auto merge of #1988 : pcwalton/servo/acid2-2, r=SimonSapin

r? @metajack @SimonSapin @larsbergstrom @june0cho @hyunjunekim

src/components/gfx/display_list.rs

@@ -18,64 +18,142 @@ use color::Color;
 use render_context::RenderContext;
 use text::TextRun;
 
-use geom::{Point2D, Rect, Size2D, SideOffsets2D};
+use geom::{Point2D, Rect, SideOffsets2D, Size2D};
 use servo_net::image::base::Image;
 use servo_util::geometry::Au;
 use servo_util::range::Range;
-use std::cast::transmute_region;
+use servo_util::smallvec::{SmallVec, SmallVec0, SmallVecIterator};
+use std::libc::uintptr_t;
+use std::mem;
 use std::vec::Items;
 use style::computed_values::border_style;
 use sync::Arc;
 
-pub struct DisplayListCollection<E> {
-    lists: ~[DisplayList<E>]
+/// An opaque handle to a node. The only safe operation that can be performed on this node is to
+/// compare it to another opaque handle or to another node.
+///
+/// Because the script task's GC does not trace layout, node data cannot be safely stored in layout
+/// data structures. Also, layout code tends to be faster when the DOM is not being accessed, for
+/// locality reasons. Using `OpaqueNode` enforces this invariant.
+#[deriving(Clone, Eq)]
+pub struct OpaqueNode(uintptr_t);
+
+impl OpaqueNode {
+    /// Returns the address of this node, for debugging purposes.
+    pub fn id(&self) -> uintptr_t {
+        let OpaqueNode(pointer) = *self;
+        pointer
+    }
 }
 
-impl<E> DisplayListCollection<E> {
-    pub fn new() -> DisplayListCollection<E> {
-        DisplayListCollection {
-            lists: ~[]
+/// A stacking context. See CSS 2.1 § E.2. "Steps" below refer to steps in that section of the
+/// specification.
+///
+/// TODO(pcwalton): Outlines.
+pub struct StackingContext {
+    /// The border and backgrounds for the root of this stacking context: steps 1 and 2.
+    background_and_borders: DisplayList,
+    /// Borders and backgrounds for block-level descendants: step 4.
+    block_backgrounds_and_borders: DisplayList,
+    /// Floats: step 5. These are treated as pseudo-stacking contexts.
+    floats: DisplayList,
+    /// All other content.
+    content: DisplayList,
+
+    /// Positioned descendant stacking contexts, along with their `z-index` levels.
+    ///
+    /// TODO(pcwalton): `z-index` should be the actual CSS property value in order to handle
+    /// `auto`, not just an integer. In this case we should store an actual stacking context, not
+    /// a flattened display list.
+    positioned_descendants: SmallVec0<(int, DisplayList)>,
+}
+
+impl StackingContext {
+    pub fn new() -> StackingContext {
+        StackingContext {
+            background_and_borders: DisplayList::new(),
+            block_backgrounds_and_borders: DisplayList::new(),
+            floats: DisplayList::new(),
+            content: DisplayList::new(),
+            positioned_descendants: SmallVec0::new(),
         }
     }
 
-    pub fn iter<'a>(&'a self) -> DisplayListIterator<'a,E> {
-        ParentDisplayListIterator(self.lists.iter())
-    }
-
-    pub fn add_list(&mut self, list: DisplayList<E>) {
-        self.lists.push(list);
-    }
-
-    pub fn draw_lists_into_context(&self, render_context: &mut RenderContext) {
-        for list in self.lists.iter() {
-            list.draw_into_context(render_context);
-        }
-        debug!("{:?}", self.dump());
-    }
-
-    fn dump(&self) {
-        let mut index = 0;
-        for list in self.lists.iter() {
-            debug!("dumping display list {:d}:", index);
-            list.dump();
-            index = index + 1;
+    pub fn list_for_background_and_border_level<'a>(
+                                                &'a mut self,
+                                                level: BackgroundAndBorderLevel)
+                                                -> &'a mut DisplayList {
+        match level {
+            RootOfStackingContextLevel => &mut self.background_and_borders,
+            BlockLevel => &mut self.block_backgrounds_and_borders,
+            ContentLevel => &mut self.content,
         }
     }
+
+    /// Flattens a stacking context into a display list according to the steps in CSS 2.1 § E.2.
+    pub fn flatten(self) -> DisplayList {
+        // Steps 1 and 2: Borders and background for the root.
+        let StackingContext {
+            background_and_borders: mut result,
+            block_backgrounds_and_borders,
+            floats,
+            content,
+            positioned_descendants: mut positioned_descendants
+        } = self;
+
+        // TODO(pcwalton): Sort positioned children according to z-index.
+
+        // Step 3: Positioned descendants with negative z-indices.
+        for &(ref mut z_index, ref mut list) in positioned_descendants.mut_iter() {
+            if *z_index < 0 {
+                result.push_all_move(mem::replace(list, DisplayList::new()))
+            }
+        }
+
+        // Step 4: Block backgrounds and borders.
+        result.push_all_move(block_backgrounds_and_borders);
+
+        // Step 5: Floats.
+        result.push_all_move(floats);
+
+        // TODO(pcwalton): Step 6: Inlines that generate stacking contexts.
+
+        // Step 7: Content.
+        result.push_all_move(content);
+
+        // Steps 8 and 9: Positioned descendants with nonnegative z-indices.
+        for &(ref mut z_index, ref mut list) in positioned_descendants.mut_iter() {
+            if *z_index >= 0 {
+                result.push_all_move(mem::replace(list, DisplayList::new()))
+            }
+        }
+
+        // TODO(pcwalton): Step 10: Outlines.
+
+        result
+    }
+}
+
+/// Which level to place backgrounds and borders in.
+pub enum BackgroundAndBorderLevel {
+    RootOfStackingContextLevel,
+    BlockLevel,
+    ContentLevel,
 }
 
 /// A list of rendering operations to be performed.
-pub struct DisplayList<E> {
-    list: ~[DisplayItem<E>]
+pub struct DisplayList {
+    list: SmallVec0<DisplayItem>,
 }
 
-pub enum DisplayListIterator<'a,E> {
+pub enum DisplayListIterator<'a> {
     EmptyDisplayListIterator,
-    ParentDisplayListIterator(Items<'a,DisplayList<E>>),
+    ParentDisplayListIterator(Items<'a,DisplayList>),
 }
 
-impl<'a,E> Iterator<&'a DisplayList<E>> for DisplayListIterator<'a,E> {
+impl<'a> Iterator<&'a DisplayList> for DisplayListIterator<'a> {
     #[inline]
-    fn next(&mut self) -> Option<&'a DisplayList<E>> {
+    fn next(&mut self) -> Option<&'a DisplayList> {
         match *self {
             EmptyDisplayListIterator => None,
             ParentDisplayListIterator(ref mut subiterator) => subiterator.next(),
@@ -83,11 +161,11 @@ impl<'a,E> Iterator<&'a DisplayList<E>> for DisplayListIterator<'a,E> {
     }
 }
 
-impl<E> DisplayList<E> {
+impl DisplayList {
     /// Creates a new display list.
-    pub fn new() -> DisplayList<E> {
+    pub fn new() -> DisplayList {
         DisplayList {
-            list: ~[]
+            list: SmallVec0::new(),
         }
     }
 
@@ -98,60 +176,62 @@ impl<E> DisplayList<E> {
     }
 
     /// Appends the given item to the display list.
-    pub fn append_item(&mut self, item: DisplayItem<E>) {
-        // FIXME(Issue #150): crashes
-        //debug!("Adding display item {:u}: {}", self.len(), item);
+    pub fn push(&mut self, item: DisplayItem) {
         self.list.push(item)
     }
 
+    /// Appends the given display list to this display list, consuming the other display list in
+    /// the process.
+    pub fn push_all_move(&mut self, other: DisplayList) {
+        self.list.push_all_move(other.list)
+    }
+
     /// Draws the display list into the given render context.
     pub fn draw_into_context(&self, render_context: &mut RenderContext) {
         debug!("Beginning display list.");
         for item in self.list.iter() {
-            // FIXME(Issue #150): crashes
-            //debug!("drawing {}", *item);
             item.draw_into_context(render_context)
         }
         debug!("Ending display list.");
     }
 
     /// Returns a preorder iterator over the given display list.
-    pub fn iter<'a>(&'a self) -> DisplayItemIterator<'a,E> {
+    pub fn iter<'a>(&'a self) -> DisplayItemIterator<'a> {
         ParentDisplayItemIterator(self.list.iter())
     }
 }
 
 /// One drawing command in the list.
-pub enum DisplayItem<E> {
-    SolidColorDisplayItemClass(~SolidColorDisplayItem<E>),
-    TextDisplayItemClass(~TextDisplayItem<E>),
-    ImageDisplayItemClass(~ImageDisplayItem<E>),
-    BorderDisplayItemClass(~BorderDisplayItem<E>),
-    LineDisplayItemClass(~LineDisplayItem<E>),
-    ClipDisplayItemClass(~ClipDisplayItem<E>)
+pub enum DisplayItem {
+    SolidColorDisplayItemClass(~SolidColorDisplayItem),
+    TextDisplayItemClass(~TextDisplayItem),
+    ImageDisplayItemClass(~ImageDisplayItem),
+    BorderDisplayItemClass(~BorderDisplayItem),
+    LineDisplayItemClass(~LineDisplayItem),
+    ClipDisplayItemClass(~ClipDisplayItem)
 }
 
 /// Information common to all display items.
-pub struct BaseDisplayItem<E> {
+pub struct BaseDisplayItem {
     /// The boundaries of the display item.
     ///
     /// TODO: Which coordinate system should this use?
     bounds: Rect<Au>,
 
-    /// Extra data: either the originating flow (for hit testing) or nothing (for rendering).
-    extra: E,
+    /// The originating DOM node.
+    node: OpaqueNode,
 }
 
 /// Renders a solid color.
-pub struct SolidColorDisplayItem<E> {
-    base: BaseDisplayItem<E>,
+pub struct SolidColorDisplayItem {
+    base: BaseDisplayItem,
     color: Color,
 }
 
 /// Renders text.
-pub struct TextDisplayItem<E> {
+pub struct TextDisplayItem {
     /// Fields common to all display items.
-    base: BaseDisplayItem<E>,
+    base: BaseDisplayItem,
 
     /// The text run.
     text_run: Arc<~TextRun>,
@@ -188,14 +268,19 @@ bitfield!(TextDisplayItemFlags, override_overline, set_override_overline, 0x02)
 bitfield!(TextDisplayItemFlags, override_line_through, set_override_line_through, 0x04)
 
 /// Renders an image.
-pub struct ImageDisplayItem<E> {
-    base: BaseDisplayItem<E>,
+pub struct ImageDisplayItem {
+    base: BaseDisplayItem,
     image: Arc<~Image>,
+
+    /// The dimensions to which the image display item should be stretched. If this is smaller than
+    /// the bounds of this display item, then the image will be repeated in the appropriate
+    /// direction to tile the entire bounds.
+    stretch_size: Size2D<Au>,
 }
 
 /// Renders a border.
-pub struct BorderDisplayItem<E> {
-    base: BaseDisplayItem<E>,
+pub struct BorderDisplayItem {
+    base: BaseDisplayItem,
 
     /// The border widths
     border: SideOffsets2D<Au>,
@@ -207,31 +292,31 @@ pub struct BorderDisplayItem<E> {
     style: SideOffsets2D<border_style::T>
 }
 
-/// Renders a line segment
-pub struct LineDisplayItem<E> {
-    base: BaseDisplayItem<E>,
+/// Renders a line segment.
+pub struct LineDisplayItem {
+    base: BaseDisplayItem,
 
     /// The line segment color.
     color: Color,
 
-    /// The line segemnt style.
+    /// The line segment style.
     style: border_style::T
 }
 
-pub struct ClipDisplayItem<E> {
-    base: BaseDisplayItem<E>,
-    child_list: ~[DisplayItem<E>],
+pub struct ClipDisplayItem {
+    base: BaseDisplayItem,
+    child_list: SmallVec0<DisplayItem>,
     need_clip: bool
 }
 
-pub enum DisplayItemIterator<'a,E> {
+pub enum DisplayItemIterator<'a> {
     EmptyDisplayItemIterator,
-    ParentDisplayItemIterator(Items<'a,DisplayItem<E>>),
+    ParentDisplayItemIterator(SmallVecIterator<'a,DisplayItem>),
 }
 
-impl<'a,E> Iterator<&'a DisplayItem<E>> for DisplayItemIterator<'a,E> {
+impl<'a> Iterator<&'a DisplayItem> for DisplayItemIterator<'a> {
     #[inline]
-    fn next(&mut self) -> Option<&'a DisplayItem<E>> {
+    fn next(&mut self) -> Option<&'a DisplayItem> {
         match *self {
             EmptyDisplayItemIterator => None,
             ParentDisplayItemIterator(ref mut subiterator) => subiterator.next(),
@@ -239,7 +324,7 @@ impl<'a,E> Iterator<&'a DisplayItem<E>> for DisplayItemIterator<'a,E> {
     }
 }
 
-impl<E> DisplayItem<E> {
+impl DisplayItem {
     /// Renders this display item into the given render context.
     fn draw_into_context(&self, render_context: &mut RenderContext) {
         match *self {
@@ -306,7 +391,22 @@ impl<E> DisplayItem<E> {
             ImageDisplayItemClass(ref image_item) => {
                 debug!("Drawing image at {:?}.", image_item.base.bounds);
 
-                render_context.draw_image(image_item.base.bounds, image_item.image.clone())
+                let mut y_offset = Au(0);
+                while y_offset < image_item.base.bounds.size.height {
+                    let mut x_offset = Au(0);
+                    while x_offset < image_item.base.bounds.size.width {
+                        let mut bounds = image_item.base.bounds;
+                        bounds.origin.x = bounds.origin.x + x_offset;
+                        bounds.origin.y = bounds.origin.y + y_offset;
+                        bounds.size = image_item.stretch_size;
+
+                        render_context.draw_image(bounds, image_item.image.clone());
+
+                        x_offset = x_offset + image_item.stretch_size.width;
+                    }
+
+                    y_offset = y_offset + image_item.stretch_size.height;
+                }
             }
 
             BorderDisplayItemClass(ref border) => {
@@ -324,17 +424,14 @@ impl<E> DisplayItem<E> {
         }
     }
 
-    pub fn base<'a>(&'a self) -> &'a BaseDisplayItem<E> {
-        // FIXME(tkuehn): Workaround for Rust region bug.
-        unsafe {
-            match *self {
-                SolidColorDisplayItemClass(ref solid_color) => transmute_region(&solid_color.base),
-                TextDisplayItemClass(ref text) => transmute_region(&text.base),
-                ImageDisplayItemClass(ref image_item) => transmute_region(&image_item.base),
-                BorderDisplayItemClass(ref border) => transmute_region(&border.base),
-                LineDisplayItemClass(ref line) => transmute_region(&line.base),
-                ClipDisplayItemClass(ref clip) => transmute_region(&clip.base),
-            }
+    pub fn base<'a>(&'a self) -> &'a BaseDisplayItem {
+        match *self {
+            SolidColorDisplayItemClass(ref solid_color) => &solid_color.base,
+            TextDisplayItemClass(ref text) => &text.base,
+            ImageDisplayItemClass(ref image_item) => &image_item.base,
+            BorderDisplayItemClass(ref border) => &border.base,
+            LineDisplayItemClass(ref line) => &line.base,
+            ClipDisplayItemClass(ref clip) => &clip.base,
         }
     }
 
@@ -342,7 +439,7 @@ impl<E> DisplayItem<E> {
         self.base().bounds
     }
 
-    pub fn children<'a>(&'a self) -> DisplayItemIterator<'a,E> {
+    pub fn children<'a>(&'a self) -> DisplayItemIterator<'a> {
         match *self {
             ClipDisplayItemClass(ref clip) => ParentDisplayItemIterator(clip.child_list.iter()),
             SolidColorDisplayItemClass(..) |

src/components/gfx/render_context.rs

@@ -5,8 +5,8 @@
 use font_context::FontContext;
 use style::computed_values::border_style;
 
-use azure::azure_hl::{B8G8R8A8, Color, ColorPattern, DrawOptions};
-use azure::azure_hl::{DrawSurfaceOptions, DrawTarget, Linear, StrokeOptions};
+use azure::azure_hl::{B8G8R8A8, Color, ColorPattern, DrawOptions, DrawSurfaceOptions, DrawTarget};
+use azure::azure_hl::{Linear, SourceOp, StrokeOptions};
 use azure::AZ_CAP_BUTT;
 use azure::AzFloat;
 use geom::point::Point2D;
@@ -45,7 +45,7 @@ impl<'a> RenderContext<'a>  {
 
     pub fn draw_solid_color(&self, bounds: &Rect<Au>, color: Color) {
         self.draw_target.make_current();
-        self.draw_target.fill_rect(&bounds.to_azure_rect(), &ColorPattern(color));
+        self.draw_target.fill_rect(&bounds.to_azure_rect(), &ColorPattern(color), None);
     }
 
     pub fn draw_border(&self,
@@ -121,13 +121,15 @@ impl<'a> RenderContext<'a>  {
     }
 
     pub fn clear(&self) {
-        let pattern = ColorPattern(Color(1.0, 1.0, 1.0, 1.0));
+        let pattern = ColorPattern(Color(0.0, 0.0, 0.0, 0.0));
         let rect = Rect(Point2D(self.page_rect.origin.x as AzFloat,
                                 self.page_rect.origin.y as AzFloat),
                         Size2D(self.screen_rect.size.width as AzFloat,
                                self.screen_rect.size.height as AzFloat));
+        let mut draw_options = DrawOptions(1.0, 0);
+        draw_options.set_composition_op(SourceOp);
         self.draw_target.make_current();
-        self.draw_target.fill_rect(&rect, &pattern);
+        self.draw_target.fill_rect(&rect, &pattern, Some(&draw_options));
     }
 
     fn draw_border_segment(&self, direction: Direction, bounds: &Rect<Au>, border: SideOffsets2D<f32>, color: SideOffsets2D<Color>, style: SideOffsets2D<border_style::T>) {

src/components/gfx/render_task.rs

@@ -2,7 +2,12 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
-// The task that handles all rendering/painting.
+//! The task that handles all rendering/painting.
+
+use buffer_map::BufferMap;
+use display_list::DisplayList;
+use font_context::{FontContext, FontContextInfo};
+use render_context::RenderContext;
 
 use azure::azure_hl::{B8G8R8A8, Color, DrawTarget, StolenGLResources};
 use azure::AzFloat;
@@ -12,12 +17,14 @@ use geom::size::Size2D;
 use layers::platform::surface::{NativePaintingGraphicsContext, NativeSurface};
 use layers::platform::surface::{NativeSurfaceMethods};
 use layers;
-use servo_msg::compositor_msg::{Epoch, IdleRenderState, LayerBuffer, LayerBufferSet};
-use servo_msg::compositor_msg::{RenderListener, RenderingRenderState};
+use servo_msg::compositor_msg::{Epoch, IdleRenderState, LayerBuffer};
+use servo_msg::compositor_msg::{LayerBufferSet, LayerId, LayerMetadata, RenderListener};
+use servo_msg::compositor_msg::{RenderingRenderState, ScrollPolicy};
 use servo_msg::constellation_msg::{ConstellationChan, PipelineId, RendererReadyMsg};
 use servo_msg::constellation_msg::{Failure, FailureMsg};
 use servo_msg::platform::surface::NativeSurfaceAzureMethods;
 use servo_util::opts::Opts;
+use servo_util::smallvec::{SmallVec, SmallVec1};
 use servo_util::time::{ProfilerChan, profile};
 use servo_util::time;
 use servo_util::task::send_on_failure;
@@ -26,20 +33,23 @@ use std::comm::{Chan, Port};
 use std::task;
 use sync::Arc;
 
-use buffer_map::BufferMap;
-use display_list::DisplayListCollection;
-use font_context::{FontContext, FontContextInfo};
-use render_context::RenderContext;
-
-pub struct RenderLayer<T> {
-    display_list_collection: Arc<DisplayListCollection<T>>,
-    size: Size2D<uint>,
-    color: Color
+/// Information about a layer that layout sends to the painting task.
+pub struct RenderLayer {
+    /// A per-pipeline ID describing this layer that should be stable across reflows.
+    id: LayerId,
+    /// The display list describing the contents of this layer.
+    display_list: Arc<DisplayList>,
+    /// The position of the layer in pixels.
+    position: Rect<uint>,
+    /// The color of the background in this layer. Used for unrendered content.
+    background_color: Color,
+    /// The scrolling policy of this layer.
+    scroll_policy: ScrollPolicy,
 }
 
-pub enum Msg<T> {
-    RenderMsg(RenderLayer<T>),
-    ReRenderMsg(~[BufferRequest], f32, Epoch),
+pub enum Msg {
+    RenderMsg(SmallVec1<RenderLayer>),
+    ReRenderMsg(~[BufferRequest], f32, LayerId, Epoch),
     UnusedBufferMsg(~[~LayerBuffer]),
     PaintPermissionGranted,
     PaintPermissionRevoked,
@@ -63,22 +73,21 @@ pub fn BufferRequest(screen_rect: Rect<uint>, page_rect: Rect<f32>) -> BufferReq
     }
 }
 
-// FIXME(rust#9155): this should be a newtype struct, but
-// generic newtypes ICE when compiled cross-crate
-pub struct RenderChan<T> {
-    chan: Chan<Msg<T>>,
+// FIXME(#2005, pcwalton): This should be a newtype struct.
+pub struct RenderChan {
+    chan: Chan<Msg>,
 }
 
-impl<T: Send> Clone for RenderChan<T> {
-    fn clone(&self) -> RenderChan<T> {
+impl Clone for RenderChan {
+    fn clone(&self) -> RenderChan {
         RenderChan {
             chan: self.chan.clone(),
         }
     }
 }
 
-impl<T: Send> RenderChan<T> {
-    pub fn new() -> (Port<Msg<T>>, RenderChan<T>) {
+impl RenderChan {
+    pub fn new() -> (Port<Msg>, RenderChan) {
         let (port, chan) = Chan::new();
         let render_chan = RenderChan {
             chan: chan,
@@ -86,11 +95,11 @@ impl<T: Send> RenderChan<T> {
         (port, render_chan)
     }
 
-    pub fn send(&self, msg: Msg<T>) {
+    pub fn send(&self, msg: Msg) {
         assert!(self.try_send(msg), "RenderChan.send: render port closed")
     }
 
-    pub fn try_send(&self, msg: Msg<T>) -> bool {
+    pub fn try_send(&self, msg: Msg) -> bool {
         self.chan.try_send(msg)
     }
 }
@@ -102,9 +111,9 @@ enum GraphicsContext {
     GpuGraphicsContext,
 }
 
-pub struct RenderTask<C,T> {
+pub struct RenderTask<C> {
     id: PipelineId,
-    port: Port<Msg<T>>,
+    port: Port<Msg>,
     compositor: C,
     constellation_chan: ConstellationChan,
     font_ctx: ~FontContext,
@@ -119,8 +128,8 @@ pub struct RenderTask<C,T> {
     /// The native graphics context.
     native_graphics_context: Option<NativePaintingGraphicsContext>,
 
-    /// The layer to be rendered
-    render_layer: Option<RenderLayer<T>>,
+    /// The layers to be rendered.
+    render_layers: SmallVec1<RenderLayer>,
 
     /// Permission to send paint messages to the compositor
     paint_permission: bool,
@@ -140,9 +149,25 @@ macro_rules! native_graphics_context(
     )
 )
 
-impl<C: RenderListener + Send,T:Send+Freeze> RenderTask<C,T> {
+fn initialize_layers<C:RenderListener>(
+                     compositor: &mut C,
+                     pipeline_id: PipelineId,
+                     epoch: Epoch,
+                     render_layers: &[RenderLayer]) {
+    let metadata = render_layers.iter().map(|render_layer| {
+        LayerMetadata {
+            id: render_layer.id,
+            position: render_layer.position,
+            background_color: render_layer.background_color,
+            scroll_policy: render_layer.scroll_policy,
+        }
+    }).collect();
+    compositor.initialize_layers_for_pipeline(pipeline_id, metadata, epoch);
+}
+
+impl<C: RenderListener + Send> RenderTask<C> {
     pub fn create(id: PipelineId,
-                  port: Port<Msg<T>>,
+                  port: Port<Msg>,
                   compositor: C,
                   constellation_chan: ConstellationChan,
                   failure_msg: Failure,
@@ -181,7 +206,7 @@ impl<C: RenderListener + Send,T:Send+Freeze> RenderTask<C,T> {
 
                     native_graphics_context: native_graphics_context,
 
-                    render_layer: None,
+                    render_layers: SmallVec1::new(),
 
                     paint_permission: false,
                     epoch: Epoch(0),
@@ -207,20 +232,25 @@ impl<C: RenderListener + Send,T:Send+Freeze> RenderTask<C,T> {
 
         loop {
             match self.port.recv() {
-                RenderMsg(render_layer) => {
-                    if self.paint_permission {
-                        self.epoch.next();
-                        self.compositor.set_layer_page_size_and_color(self.id, render_layer.size, self.epoch, render_layer.color);
-                    } else {
+                RenderMsg(render_layers) => {
+                    self.epoch.next();
+                    self.render_layers = render_layers;
+
+                    if !self.paint_permission {
                         debug!("render_task: render ready msg");
                         let ConstellationChan(ref mut c) = self.constellation_chan;
                         c.send(RendererReadyMsg(self.id));
+                        continue;
                     }
-                    self.render_layer = Some(render_layer);
+
+                    initialize_layers(&mut self.compositor,
+                                      self.id,
+                                      self.epoch,
+                                      self.render_layers.as_slice());
                 }
-                ReRenderMsg(tiles, scale, epoch) => {
+                ReRenderMsg(tiles, scale, layer_id, epoch) => {
                     if self.epoch == epoch {
-                        self.render(tiles, scale);
+                        self.render(tiles, scale, layer_id);
                     } else {
                         debug!("renderer epoch mismatch: {:?} != {:?}", self.epoch, epoch);
                     }
@@ -233,12 +263,16 @@ impl<C: RenderListener + Send,T:Send+Freeze> RenderTask<C,T> {
                 }
                 PaintPermissionGranted => {
                     self.paint_permission = true;
-                    match self.render_layer {
-                        Some(ref render_layer) => {
-                            self.epoch.next();
-                            self.compositor.set_layer_page_size_and_color(self.id, render_layer.size, self.epoch, render_layer.color);
-                        }
-                        None => {}
+
+                    // Here we assume that the main layer—the layer responsible for the page size—
+                    // is the first layer. This is a pretty fragile assumption. It will be fixed
+                    // once we use the layers-based scrolling infrastructure for all scrolling.
+                    if self.render_layers.len() > 1 {
+                        self.epoch.next();
+                        initialize_layers(&mut self.compositor,
+                                          self.id,
+                                          self.epoch,
+                                          self.render_layers.as_slice());
                     }
                 }
                 PaintPermissionRevoked => {
@@ -253,138 +287,144 @@ impl<C: RenderListener + Send,T:Send+Freeze> RenderTask<C,T> {
         }
     }
 
-    fn render(&mut self, tiles: ~[BufferRequest], scale: f32) {
-        if self.render_layer.is_none() {
-            return
-        }
-
-        self.compositor.set_render_state(RenderingRenderState);
+    /// Renders one layer and sends the tiles back to the layer.
+    ///
+    /// FIXME(pcwalton): We will probably want to eventually send all layers belonging to a page in
+    /// one transaction, to avoid the user seeing inconsistent states.
+    fn render(&mut self, tiles: ~[BufferRequest], scale: f32, layer_id: LayerId) {
         time::profile(time::RenderingCategory, self.profiler_chan.clone(), || {
             // FIXME: Try not to create a new array here.
             let mut new_buffers = ~[];
 
-            // Divide up the layer into tiles.
-            time::profile(time::RenderingPrepBuffCategory, self.profiler_chan.clone(), || {
-                for tile in tiles.iter() {
-                    let width = tile.screen_rect.size.width;
-                    let height = tile.screen_rect.size.height;
+            // Find the appropriate render layer.
+            let render_layer = match self.render_layers.iter().find(|layer| layer.id == layer_id) {
+                Some(render_layer) => render_layer,
+                None => return,
+            };
 
-                    let size = Size2D(width as i32, height as i32);
-                    let draw_target = match self.graphics_context {
-                        CpuGraphicsContext => {
-                            DrawTarget::new(self.opts.render_backend, size, B8G8R8A8)
-                        }
-                        GpuGraphicsContext => {
-                            // FIXME(pcwalton): Cache the components of draw targets
-                            // (texture color buffer, renderbuffers) instead of recreating them.
-                            let draw_target =
-                                DrawTarget::new_with_fbo(self.opts.render_backend,
-                                                         native_graphics_context!(self),
-                                                         size,
-                                                         B8G8R8A8);
-                            draw_target.make_current();
-                            draw_target
-                        }
+            self.compositor.set_render_state(RenderingRenderState);
+
+            // Divide up the layer into tiles.
+            for tile in tiles.iter() {
+                let width = tile.screen_rect.size.width;
+                let height = tile.screen_rect.size.height;
+
+                let size = Size2D(width as i32, height as i32);
+                let draw_target = match self.graphics_context {
+                    CpuGraphicsContext => {
+                        DrawTarget::new(self.opts.render_backend, size, B8G8R8A8)
+                    }
+                    GpuGraphicsContext => {
+                        // FIXME(pcwalton): Cache the components of draw targets
+                        // (texture color buffer, renderbuffers) instead of recreating them.
+                        let draw_target =
+                            DrawTarget::new_with_fbo(self.opts.render_backend,
+                                                     native_graphics_context!(self),
+                                                     size,
+                                                     B8G8R8A8);
+                        draw_target.make_current();
+                        draw_target
+                    }
+                };
+
+                {
+                    // Build the render context.
+                    let mut ctx = RenderContext {
+                        draw_target: &draw_target,
+                        font_ctx: &mut self.font_ctx,
+                        opts: &self.opts,
+                        page_rect: tile.page_rect,
+                        screen_rect: tile.screen_rect,
                     };
 
-                    {
-                        // Build the render context.
-                        let mut ctx = RenderContext {
-                            draw_target: &draw_target,
-                            font_ctx: &mut self.font_ctx,
-                            opts: &self.opts,
-                            page_rect: tile.page_rect,
-                            screen_rect: tile.screen_rect,
+                    // Apply the translation to render the tile we want.
+                    let matrix: Matrix2D<AzFloat> = Matrix2D::identity();
+                    let matrix = matrix.scale(scale as AzFloat, scale as AzFloat);
+                    let matrix = matrix.translate(-(tile.page_rect.origin.x) as AzFloat,
+                                                  -(tile.page_rect.origin.y) as AzFloat);
+                    let matrix = matrix.translate(-(render_layer.position.origin.x as AzFloat),
+                                                  -(render_layer.position.origin.y as AzFloat));
+
+                    ctx.draw_target.set_transform(&matrix);
+
+                    // Clear the buffer.
+                    ctx.clear();
+
+                    // Draw the display list.
+                    profile(time::RenderingDrawingCategory, self.profiler_chan.clone(), || {
+                        render_layer.display_list.get().draw_into_context(&mut ctx);
+                        ctx.draw_target.flush();
+                    });
+                }
+
+                // Extract the texture from the draw target and place it into its slot in the
+                // buffer. If using CPU rendering, upload it first.
+                //
+                // FIXME(pcwalton): We should supply the texture and native surface *to* the
+                // draw target in GPU rendering mode, so that it doesn't have to recreate it.
+                let buffer = match self.graphics_context {
+                    CpuGraphicsContext => {
+                        let buffer = match self.buffer_map.find(tile.screen_rect.size) {
+                            Some(buffer) => {
+                                let mut buffer = buffer;
+                                buffer.rect = tile.page_rect;
+                                buffer.screen_pos = tile.screen_rect;
+                                buffer.resolution = scale;
+                                buffer.native_surface.mark_wont_leak();
+                                buffer
+                            }
+                            None => {
+                                // Create an empty native surface. We mark it as not leaking
+                                // in case it dies in transit to the compositor task.
+                                let mut native_surface: NativeSurface =
+                                    layers::platform::surface::NativeSurfaceMethods::new(
+                                        native_graphics_context!(self),
+                                        Size2D(width as i32, height as i32),
+                                        width as i32 * 4);
+                                native_surface.mark_wont_leak();
+
+                                ~LayerBuffer {
+                                    native_surface: native_surface,
+                                    rect: tile.page_rect,
+                                    screen_pos: tile.screen_rect,
+                                    resolution: scale,
+                                    stride: (width * 4) as uint
+                                }
+                            }
                         };
 
-                        // Apply the translation to render the tile we want.
-                        let matrix: Matrix2D<AzFloat> = Matrix2D::identity();
-                        let matrix = matrix.scale(scale as AzFloat, scale as AzFloat);
-                        let matrix = matrix.translate(-(tile.page_rect.origin.x) as AzFloat,
-                                                      -(tile.page_rect.origin.y) as AzFloat);
-                        
-                        ctx.draw_target.set_transform(&matrix);
-                        
-                        // Clear the buffer.
-                        ctx.clear();
-                        
-                        // Draw the display list.
-                        profile(time::RenderingDrawingCategory, self.profiler_chan.clone(), || {
-                            let render_layer = self.render_layer.as_ref().unwrap();
-                            render_layer.display_list_collection.get().draw_lists_into_context(&mut ctx);
-                            ctx.draw_target.flush();
+                        draw_target.snapshot().get_data_surface().with_data(|data| {
+                            buffer.native_surface.upload(native_graphics_context!(self), data);
+                            debug!("RENDERER uploading to native surface {:d}",
+                                   buffer.native_surface.get_id() as int);
                         });
+
+                        buffer
                     }
+                    GpuGraphicsContext => {
+                        draw_target.make_current();
+                        let StolenGLResources {
+                            surface: native_surface
+                        } = draw_target.steal_gl_resources().unwrap();
 
-                    // Extract the texture from the draw target and place it into its slot in the
-                    // buffer. If using CPU rendering, upload it first.
-                    //
-                    // FIXME(pcwalton): We should supply the texture and native surface *to* the
-                    // draw target in GPU rendering mode, so that it doesn't have to recreate it.
-                    let buffer = match self.graphics_context {
-                        CpuGraphicsContext => {
-                            let buffer = match self.buffer_map.find(tile.screen_rect.size) {
-                                Some(buffer) => {
-                                    let mut buffer = buffer;
-                                    buffer.rect = tile.page_rect;
-                                    buffer.screen_pos = tile.screen_rect;
-                                    buffer.resolution = scale;
-                                    buffer.native_surface.mark_wont_leak();
-                                    buffer
-                                }
-                                None => {
-                                    // Create an empty native surface. We mark it as not leaking
-                                    // in case it dies in transit to the compositor task.
-                                    let mut native_surface: NativeSurface =
-                                        layers::platform::surface::NativeSurfaceMethods::new(
-                                            native_graphics_context!(self),
-                                            Size2D(width as i32, height as i32),
-                                            width as i32 * 4);
-                                    native_surface.mark_wont_leak();
+                        // We mark the native surface as not leaking in case the surfaces
+                        // die on their way to the compositor task.
+                        let mut native_surface: NativeSurface =
+                            NativeSurfaceAzureMethods::from_azure_surface(native_surface);
+                        native_surface.mark_wont_leak();
 
-                                    ~LayerBuffer {
-                                        native_surface: native_surface,
-                                        rect: tile.page_rect,
-                                        screen_pos: tile.screen_rect,
-                                        resolution: scale,
-                                        stride: (width * 4) as uint
-                                    }
-                                }
-                            };
-
-                            draw_target.snapshot().get_data_surface().with_data(|data| {
-                                buffer.native_surface.upload(native_graphics_context!(self), data);
-                                debug!("RENDERER uploading to native surface {:d}",
-                                       buffer.native_surface.get_id() as int);
-                            });
-
-                            buffer
+                        ~LayerBuffer {
+                            native_surface: native_surface,
+                            rect: tile.page_rect,
+                            screen_pos: tile.screen_rect,
+                            resolution: scale,
+                            stride: (width * 4) as uint
                         }
-                        GpuGraphicsContext => {
-                            draw_target.make_current();
-                            let StolenGLResources {
-                                surface: native_surface
-                            } = draw_target.steal_gl_resources().unwrap();
+                    }
+                };
 
-                            // We mark the native surface as not leaking in case the surfaces
-                            // die on their way to the compositor task.
-                            let mut native_surface: NativeSurface =
-                                NativeSurfaceAzureMethods::from_azure_surface(native_surface);
-                            native_surface.mark_wont_leak();
-
-                            ~LayerBuffer {
-                                native_surface: native_surface,
-                                rect: tile.page_rect,
-                                screen_pos: tile.screen_rect,
-                                resolution: scale,
-                                stride: (width * 4) as uint
-                            }
-                        }
-                    };
-                    
-                    new_buffers.push(buffer);
-                }
-            });
+                new_buffers.push(buffer);
+            }
 
             let layer_buffer_set = ~LayerBufferSet {
                 buffers: new_buffers,
@@ -392,7 +432,7 @@ impl<C: RenderListener + Send,T:Send+Freeze> RenderTask<C,T> {
 
             debug!("render_task: returning surface");
             if self.paint_permission {
-                self.compositor.paint(self.id, layer_buffer_set, self.epoch);
+                self.compositor.paint(self.id, render_layer.id, layer_buffer_set, self.epoch);
             } else {
                 debug!("render_task: RendererReadyMsg send");
                 let ConstellationChan(ref mut c) = self.constellation_chan;

src/components/main/compositing/compositor.rs

@@ -5,16 +5,13 @@
 use constellation::SendableFrameTree;
 use compositing::compositor_layer::CompositorLayer;
 use compositing::*;
-
+use pipeline::CompositionPipeline;
 use platform::{Application, Window};
-
-use windowing::{WindowEvent, WindowMethods,
-                WindowNavigateMsg,
-                IdleWindowEvent, RefreshWindowEvent, ResizeWindowEvent, LoadUrlWindowEvent,
-                MouseWindowEventClass, MouseWindowMoveEventClass,ScrollWindowEvent, ZoomWindowEvent, NavigationWindowEvent,
-                FinishedWindowEvent, QuitWindowEvent,
-                MouseWindowEvent, MouseWindowClickEvent, MouseWindowMouseDownEvent, MouseWindowMouseUpEvent};
-
+use windowing::{FinishedWindowEvent, IdleWindowEvent, LoadUrlWindowEvent, MouseWindowClickEvent};
+use windowing::{MouseWindowEvent, MouseWindowEventClass, MouseWindowMouseDownEvent};
+use windowing::{MouseWindowMouseUpEvent, MouseWindowMoveEventClass, NavigationWindowEvent};
+use windowing::{QuitWindowEvent, RefreshWindowEvent, ResizeWindowEvent, ScrollWindowEvent};
+use windowing::{WindowEvent, WindowMethods, WindowNavigateMsg, ZoomWindowEvent};
 
 use azure::azure_hl::{SourceSurfaceMethods, Color};
 use azure::azure_hl;
@@ -29,8 +26,10 @@ use layers::rendergl::RenderContext;
 use layers::scene::Scene;
 use opengles::gl2;
 use png;
-use servo_msg::compositor_msg::{Blank, Epoch, FinishedLoading, IdleRenderState, LayerBufferSet, ReadyState, RenderState};
-use servo_msg::constellation_msg::{ConstellationChan, ExitMsg, NavigateMsg, ResizedWindowMsg, LoadUrlMsg, PipelineId};
+use servo_msg::compositor_msg::{Blank, Epoch, FinishedLoading, IdleRenderState, LayerBufferSet};
+use servo_msg::compositor_msg::{LayerId, ReadyState, RenderState, ScrollPolicy, Scrollable};
+use servo_msg::constellation_msg::{ConstellationChan, ExitMsg, LoadUrlMsg, NavigateMsg};
+use servo_msg::constellation_msg::{PipelineId, ResizedWindowMsg};
 use servo_msg::constellation_msg;
 use servo_util::opts::Opts;
 use servo_util::time::{profile, ProfilerChan, Timer};
@@ -55,6 +54,9 @@ pub struct IOCompositor {
     /// The root ContainerLayer.
     root_layer: Rc<ContainerLayer>,
 
+    /// The root pipeline.
+    root_pipeline: Option<CompositionPipeline>,
+
     /// The canvas to paint a page.
     scene: Scene,
 
@@ -110,7 +112,6 @@ pub struct IOCompositor {
 }
 
 impl IOCompositor {
-
     pub fn new(app: &Application,
                opts: Opts,
                port: Port<Msg>,
@@ -131,6 +132,7 @@ impl IOCompositor {
             opts: opts,
             context: rendergl::init_render_context(),
             root_layer: root_layer.clone(),
+            root_pipeline: None,
             scene: Scene(ContainerLayerKind(root_layer), window_size, identity()),
             window_size: Size2D(window_size.width as uint, window_size.height as uint),
             graphics_context: CompositorTask::create_graphics_context(),
@@ -253,11 +255,10 @@ impl IOCompositor {
                     self.change_render_state(render_state);
                 }
 
-                (Data(SetUnRenderedColor(_id, color)), false) => {
-                    self.set_unrendered_color(_id, color);
+                (Data(SetUnRenderedColor(pipeline_id, layer_id, color)), false) => {
+                    self.set_unrendered_color(pipeline_id, layer_id, color);
                 }
 
-
                 (Data(SetIds(frame_tree, response_chan, new_constellation_chan)), _) => {
                     self.set_ids(frame_tree, response_chan, new_constellation_chan);
                 }
@@ -266,32 +267,44 @@ impl IOCompositor {
                     chan.send(Some(azure_hl::current_graphics_metadata()));
                 }
 
-                (Data(NewLayer(_id, new_size)), false) => {
-                    self.create_new_layer(_id, new_size);
+                (Data(CreateRootCompositorLayerIfNecessary(pipeline_id, layer_id, size)),
+                 false) => {
+                    self.create_root_compositor_layer_if_necessary(pipeline_id, layer_id, size);
                 }
 
-                (Data(SetLayerPageSize(id, new_size, epoch)), false) => {
-                    self.set_layer_page_size(id, new_size, epoch);
+                (Data(CreateDescendantCompositorLayerIfNecessary(pipeline_id,
+                                                                 layer_id,
+                                                                 rect,
+                                                                 scroll_behavior)),
+                 false) => {
+                    self.create_descendant_compositor_layer_if_necessary(pipeline_id,
+                                                                         layer_id,
+                                                                         rect,
+                                                                         scroll_behavior);
                 }
 
-                (Data(SetLayerClipRect(id, new_rect)), false) => {
-                    self.set_layer_clip_rect(id, new_rect);
+                (Data(SetLayerPageSize(pipeline_id, layer_id, new_size, epoch)), false) => {
+                    self.set_layer_page_size(pipeline_id, layer_id, new_size, epoch);
                 }
 
-                (Data(DeleteLayer(id)), _) => {
+                (Data(SetLayerClipRect(pipeline_id, layer_id, new_rect)), false) => {
+                    self.set_layer_clip_rect(pipeline_id, layer_id, new_rect);
+                }
+
+                (Data(DeleteLayerGroup(id)), _) => {
                     self.delete_layer(id);
                 }
 
-                (Data(Paint(id, new_layer_buffer_set, epoch)), false) => {
-                    self.paint(id, new_layer_buffer_set, epoch);
+                (Data(Paint(pipeline_id, layer_id, new_layer_buffer_set, epoch)), false) => {
+                    self.paint(pipeline_id, layer_id, new_layer_buffer_set, epoch);
                 }
 
-                (Data(InvalidateRect(id, rect)), false) => {
-                    self.invalidate_rect(id, rect);
+                (Data(InvalidateRect(pipeline_id, layer_id, rect)), false) => {
+                    self.invalidate_rect(pipeline_id, layer_id, rect);
                 }
 
-                (Data(ScrollFragmentPoint(id, point)), false) => {
-                    self.scroll_fragment_to_point(id, point);
+                (Data(ScrollFragmentPoint(pipeline_id, layer_id, point)), false) => {
+                    self.scroll_fragment_to_point(pipeline_id, layer_id, point);
                 }
 
                 (Data(LoadComplete(..)), false) => {
@@ -313,11 +326,10 @@ impl IOCompositor {
         }
     }
 
-    fn set_unrendered_color(&mut self, _id: PipelineId, color: Color) {
+    // FIXME(#2004, pcwalton): Take the pipeline ID and layer ID into account.
+    fn set_unrendered_color(&mut self, _: PipelineId, _: LayerId, color: Color) {
         match self.compositor_layer {
-            Some(ref mut layer) => {
-                layer.unrendered_color = color;
-            }
+            Some(ref mut layer) => layer.unrendered_color = color,
             None => {}
         }
     }
@@ -328,31 +340,7 @@ impl IOCompositor {
                new_constellation_chan: ConstellationChan) {
         response_chan.send(());
 
-        // This assumes there is at most one child, which should be the case.
-        // NOTE: work around borrowchk
-        {
-            let tmp = self.root_layer.borrow().first_child.borrow();
-            match *tmp.get() {
-                Some(ref old_layer) => ContainerLayer::remove_child(self.root_layer.clone(),
-                                                                     old_layer.clone()),
-                None => {}
-            }
-        }
-
-        let layer = CompositorLayer::from_frame_tree(frame_tree,
-                                                     self.opts.tile_size,
-                                                     Some(10000000u),
-                                                     self.opts.cpu_painting);
-        ContainerLayer::add_child_start(self.root_layer.clone(),
-                                        ContainerLayerKind(layer.root_layer.clone()));
-
-        // If there's already a root layer, destroy it cleanly.
-        match self.compositor_layer {
-            None => {}
-            Some(ref mut compositor_layer) => compositor_layer.clear_all(),
-        }
-
-        self.compositor_layer = Some(layer);
+        self.root_pipeline = Some(frame_tree.pipeline.clone());
 
         // Initialize the new constellation channel by sending it the root window size.
         let window_size = self.window.borrow().size();
@@ -366,39 +354,81 @@ impl IOCompositor {
         self.constellation_chan = new_constellation_chan;
     }
 
-    fn create_new_layer(&mut self, _id: PipelineId, new_size: Size2D<f32>) {
-        // FIXME: This should create an additional layer instead of replacing the current one.
-        // Once ResizeLayer messages are set up, we can switch to the new functionality.
+    // FIXME(pcwalton): Take the pipeline ID into account.
+    fn create_root_compositor_layer_if_necessary(&mut self,
+                                                 _: PipelineId,
+                                                 layer_id: LayerId,
+                                                 size: Size2D<f32>) {
+        let (root_pipeline, root_layer_id) = match self.compositor_layer {
+            Some(ref compositor_layer) => {
+                (compositor_layer.pipeline.clone(), compositor_layer.id_of_first_child())
+            }
+            None => {
+                match self.root_pipeline {
+                    Some(ref root_pipeline) => (root_pipeline.clone(), LayerId::null()),
+                    None => fail!("Compositor: Received new layer without initialized pipeline"),
+                }
+            }
+        };
 
-        let p = match self.compositor_layer {
-            Some(ref compositor_layer) => compositor_layer.pipeline.clone(),
+        if layer_id != root_layer_id {
+            let root_pipeline_id = root_pipeline.id;
+            let mut new_layer = CompositorLayer::new_root(root_pipeline,
+                                                          size,
+                                                          self.opts.tile_size,
+                                                          self.opts.cpu_painting);
+
+            {
+                let current_child = self.root_layer.borrow().first_child.borrow();
+                match *current_child.get() {
+                    None => {}
+                    Some(ref old_layer) => {
+                        ContainerLayer::remove_child(self.root_layer.clone(), old_layer.clone())
+                    }
+                }
+            }
+
+            assert!(new_layer.add_child_if_necessary(self.root_layer.clone(),
+                                                     root_pipeline_id,
+                                                     new_layer.id,
+                                                     layer_id,
+                                                     Rect(Point2D(0f32, 0f32), size),
+                                                     size,
+                                                     Scrollable));
+
+            ContainerLayer::add_child_start(self.root_layer.clone(),
+                                            ContainerLayerKind(new_layer.root_layer.clone()));
+            self.compositor_layer = Some(new_layer);
+        }
+
+        self.ask_for_tiles();
+    }
+
+    fn create_descendant_compositor_layer_if_necessary(&mut self,
+                                                       pipeline_id: PipelineId,
+                                                       layer_id: LayerId,
+                                                       rect: Rect<f32>,
+                                                       scroll_policy: ScrollPolicy) {
+        match self.compositor_layer {
+            Some(ref mut compositor_layer) => {
+                assert!(compositor_layer.add_child_if_necessary(self.root_layer.clone(),
+                                                                pipeline_id,
+                                                                compositor_layer.id,
+                                                                layer_id,
+                                                                rect,
+                                                                compositor_layer.page_size
+                                                                                .unwrap(),
+                                                                scroll_policy))
+            }
             None => fail!("Compositor: Received new layer without initialized pipeline"),
         };
-        let page_size = Size2D(new_size.width as f32, new_size.height as f32);
-        let new_layer = CompositorLayer::new(p,
-                                             Some(page_size),
-                                             self.opts.tile_size,
-                                             Some(10000000u),
-                                             self.opts.cpu_painting);
-
-        {
-            let current_child = self.root_layer.borrow().first_child.borrow();
-            // This assumes there is at most one child, which should be the case.
-            match *current_child.get() {
-                Some(ref old_layer) => ContainerLayer::remove_child(self.root_layer.clone(),
-                                                                     old_layer.clone()),
-                None => {}
-            }
-        }
-        ContainerLayer::add_child_start(self.root_layer.clone(),
-                                        ContainerLayerKind(new_layer.root_layer.clone()));
-        self.compositor_layer = Some(new_layer);
 
         self.ask_for_tiles();
     }
 
     fn set_layer_page_size(&mut self,
-                           id: PipelineId,
+                           pipeline_id: PipelineId,
+                           layer_id: LayerId,
                            new_size: Size2D<f32>,
                            epoch: Epoch) {
         let (ask, move): (bool, bool) = match self.compositor_layer {
@@ -407,8 +437,10 @@ impl IOCompositor {
                 let world_zoom = self.world_zoom;
                 let page_window = Size2D(window_size.width as f32 / world_zoom,
                                          window_size.height as f32 / world_zoom);
-                layer.resize(id, new_size, page_window, epoch);
-                let move = self.fragment_point.take().map_or(false, |point| layer.move(point, page_window));
+                layer.resize(pipeline_id, layer_id, new_size, page_window, epoch);
+                let move = self.fragment_point.take().map_or(false, |point| {
+                    layer.move(pipeline_id, layer_id, point, page_window)
+                });
 
                 (true, move)
             }
@@ -421,10 +453,13 @@ impl IOCompositor {
         }
     }
 
-    fn set_layer_clip_rect(&mut self, id: PipelineId, new_rect: Rect<f32>) {
+    fn set_layer_clip_rect(&mut self,
+                           pipeline_id: PipelineId,
+                           layer_id: LayerId,
+                           new_rect: Rect<f32>) {
         let ask: bool = match self.compositor_layer {
             Some(ref mut layer) => {
-                assert!(layer.set_clipping_rect(id, new_rect));
+                assert!(layer.set_clipping_rect(pipeline_id, layer_id, new_rect));
                 true
             }
             None => {
@@ -454,10 +489,11 @@ impl IOCompositor {
     }
 
     fn paint(&mut self,
-             id: PipelineId,
+             pipeline_id: PipelineId,
+             layer_id: LayerId,
              new_layer_buffer_set: ~LayerBufferSet,
              epoch: Epoch) {
-        debug!("osmain: received new frame");
+        debug!("compositor received new frame");
 
         // From now on, if we destroy the buffers, they will leak.
         let mut new_layer_buffer_set = new_layer_buffer_set;
@@ -466,27 +502,29 @@ impl IOCompositor {
         match self.compositor_layer {
             Some(ref mut layer) => {
                 assert!(layer.add_buffers(&self.graphics_context,
-                                          id,
+                                          pipeline_id,
+                                          layer_id,
                                           new_layer_buffer_set,
                                           epoch).is_none());
                 self.recomposite = true;
             }
             None => {
-                fail!("Compositor: given paint command with no CompositorLayer initialized");
+                fail!("compositor given paint command with no CompositorLayer initialized");
             }
         }
+
         // TODO: Recycle the old buffers; send them back to the renderer to reuse if
         // it wishes.
     }
 
-    fn invalidate_rect(&mut self, id: PipelineId, rect: Rect<uint>) {
+    fn invalidate_rect(&mut self, pipeline_id: PipelineId, layer_id: LayerId, rect: Rect<uint>) {
         let ask: bool = match self.compositor_layer {
             Some(ref mut layer) => {
                 let point = Point2D(rect.origin.x as f32,
                                     rect.origin.y as f32);
                 let size = Size2D(rect.size.width as f32,
                                   rect.size.height as f32);
-                layer.invalidate_rect(id, Rect(point, size));
+                layer.invalidate_rect(pipeline_id, layer_id, Rect(point, size));
                 true
             }
             None => {
@@ -500,14 +538,18 @@ impl IOCompositor {
         }
     }
 
-    fn scroll_fragment_to_point(&mut self, id: PipelineId, point: Point2D<f32>) {
+    fn scroll_fragment_to_point(&mut self,
+                                pipeline_id: PipelineId,
+                                layer_id: LayerId,
+                                point: Point2D<f32>) {
         let world_zoom = self.world_zoom;
         let page_window = Size2D(self.window_size.width as f32 / world_zoom,
                                  self.window_size.height as f32 / world_zoom);
-        let (ask, move): (bool, bool) = match self.compositor_layer {
-            Some(ref mut layer) if layer.pipeline.id == id && !layer.hidden => {
 
-                (true, layer.move(point, page_window))
+        let (ask, move): (bool, bool) = match self.compositor_layer {
+            Some(ref mut layer) if layer.pipeline.id == pipeline_id && !layer.hidden => {
+
+                (true, layer.move(pipeline_id, layer_id, point, page_window))
             }
             Some(_) | None => {
                 self.fragment_point = Some(point);
@@ -630,7 +672,7 @@ impl IOCompositor {
                                  self.window_size.height as f32 / world_zoom);
         let mut scroll = false;
         for layer in self.compositor_layer.mut_iter() {
-            scroll = layer.scroll(page_delta, page_cursor, page_window) || scroll;
+            scroll = layer.handle_scroll_event(page_delta, page_cursor, page_window) || scroll;
         }
         self.recomposite_if(scroll);
         self.ask_for_tiles();
@@ -656,7 +698,7 @@ impl IOCompositor {
         let page_window = Size2D(window_size.width as f32 / world_zoom,
                                  window_size.height as f32 / world_zoom);
         for layer in self.compositor_layer.mut_iter() {
-            layer.scroll(page_delta, page_cursor, page_window);
+            layer.handle_scroll_event(page_delta, page_cursor, page_window);
         }
 
         self.recomposite = true;
@@ -679,7 +721,9 @@ impl IOCompositor {
         for layer in self.compositor_layer.mut_iter() {
             if !layer.hidden {
                 let rect = Rect(Point2D(0f32, 0f32), window_size_page);
-                let recomposite = layer.get_buffer_request(&self.graphics_context, rect, world_zoom) ||
+                let recomposite = layer.get_buffer_request(&self.graphics_context,
+                                                           rect,
+                                                           world_zoom) ||
                                   self.recomposite;
                 self.recomposite = recomposite;
             } else {
@@ -756,3 +800,4 @@ impl IOCompositor {
         self.recomposite = result || self.recomposite;
     }
 }
+

src/components/main/compositing/compositor_layer.rs

@@ -3,42 +3,56 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use compositing::quadtree::{Quadtree, Normal, Invalid, Hidden};
-use constellation::{SendableChildFrameTree, SendableFrameTree};
+use pipeline::CompositionPipeline;
+use windowing::{MouseWindowEvent, MouseWindowClickEvent, MouseWindowMouseDownEvent};
+use windowing::{MouseWindowMouseUpEvent};
+
+use azure::azure_hl::Color;
 use geom::matrix::identity;
 use geom::point::Point2D;
 use geom::rect::Rect;
 use geom::size::Size2D;
 use gfx::render_task::{ReRenderMsg, UnusedBufferMsg};
+use gfx;
 use layers::layers::{ContainerLayerKind, ContainerLayer, Flip, NoFlip, TextureLayer};
 use layers::layers::TextureLayerKind;
-#[cfg(target_os="macos")] 
-#[cfg(target_os="android")]
-use layers::layers::VerticalFlip;
 use layers::platform::surface::{NativeCompositingGraphicsContext, NativeSurfaceMethods};
 use layers::texturegl::{Texture, TextureTarget};
-#[cfg(target_os="macos")] use layers::texturegl::TextureTargetRectangle;
-use pipeline::CompositionPipeline;
 use script::dom::event::{ClickEvent, MouseDownEvent, MouseMoveEvent, MouseUpEvent};
 use script::script_task::{ScriptChan, SendEventMsg};
-use servo_msg::compositor_msg::{LayerBuffer, LayerBufferSet, Epoch, Tile};
+use servo_msg::compositor_msg::{Epoch, FixedPosition, LayerBuffer, LayerBufferSet, LayerId};
+use servo_msg::compositor_msg::{ScrollPolicy, Tile};
 use servo_msg::constellation_msg::PipelineId;
 use std::cmp;
 use std::rc::Rc;
-use windowing::{MouseWindowEvent, MouseWindowClickEvent, MouseWindowMouseDownEvent};
-use windowing::{MouseWindowMouseUpEvent};
-use azure::azure_hl::Color;
-use gfx;
 
+#[cfg(target_os="macos")]
+#[cfg(target_os="android")]
+use layers::layers::VerticalFlip;
 #[cfg(not(target_os="macos"))]
 use layers::texturegl::TextureTarget2D;
+#[cfg(target_os="macos")]
+use layers::texturegl::TextureTargetRectangle;
+
+/// The amount of memory usage allowed per layer.
+static MAX_TILE_MEMORY_PER_LAYER: uint = 10000000;
 
 /// The CompositorLayer represents an element on a page that has a unique scroll
 /// or animation behavior. This can include absolute positioned elements, iframes, etc.
 /// Each layer can also have child layers.
+///
+/// FIXME(#2003, pcwalton): This should be merged with the concept of a layer in `rust-layers` and
+/// ultimately removed, except as a set of helper methods on `rust-layers` layers.
 pub struct CompositorLayer {
     /// This layer's pipeline. BufferRequests and mouse events will be sent through this.
     pipeline: CompositionPipeline,
 
+    /// The ID of this layer within the pipeline.
+    id: LayerId,
+
+    /// The bounds of this layer in terms of its parent (a.k.a. the scissor box).
+    bounds: Rect<f32>,
+
     /// The size of the underlying page in page coordinates. This is an option
     /// because we may not know the size of the page until layout is finished completely.
     /// if we have no size yet, the layer is hidden until a size message is recieved.
@@ -70,17 +84,20 @@ pub struct CompositorLayer {
     epoch: Epoch,
 
     /// The behavior of this layer when a scroll message is received. 
-    scroll_behavior: ScrollBehavior,
+    wants_scroll_events: WantsScrollEventsFlag,
+
+    /// Whether an ancestor layer that receives scroll events moves this layer.
+    scroll_policy: ScrollPolicy,
 
     /// True if CPU rendering is enabled, false if we're using GPU rendering.
     cpu_painting: bool,
 
     /// The color to use for the unrendered-content void
-    unrendered_color: Color
+    unrendered_color: Color,
 }
 
 /// Helper struct for keeping CompositorLayer children organized.
-struct CompositorLayerChild {
+pub struct CompositorLayerChild {
     /// The child itself.
     child: ~CompositorLayer,
     /// A ContainerLayer managed by the parent node. This deals with clipping and
@@ -95,13 +112,28 @@ enum MaybeQuadtree {
     NoTree(uint, Option<uint>),
 }
 
-/// Determines the behavior of the layer when a scroll message is recieved.
-enum ScrollBehavior {
-    /// Normal scrolling behavior.
-    Scroll,
-    /// Scrolling messages targeted at this layer are ignored, but can be
-    /// passed on to child layers.
-    FixedPosition,
+impl MaybeQuadtree {
+    fn tile_size(&self) -> uint {
+        match *self {
+            Tree(ref quadtree) => quadtree.max_tile_size,
+            NoTree(tile_size, _) => tile_size,
+        }
+    }
+}
+
+#[deriving(Eq, Clone)]
+pub enum WantsScrollEventsFlag {
+    WantsScrollEvents,
+    DoesntWantScrollEvents,
+}
+
+fn create_container_layer_from_rect(rect: Rect<f32>) -> Rc<ContainerLayer> {
+    let container = Rc::new(ContainerLayer());
+    container.borrow().scissor.set(Some(rect));
+    container.borrow().common.with_mut(|common| {
+        common.transform = identity().translate(rect.origin.x, rect.origin.y, 0f32);
+    });
+    container
 }
 
 trait Clampable {
@@ -124,79 +156,155 @@ impl Clampable for f32 {
 
 
 impl CompositorLayer {
-    /// Creates a new CompositorLayer with an optional page size. If no page size is given,
-    /// the layer is initially hidden and initialized without a quadtree.
-    pub fn new(pipeline: CompositionPipeline,
-               page_size: Option<Size2D<f32>>,
-               tile_size: uint,
-               max_mem: Option<uint>,
-               cpu_painting: bool)
-               -> CompositorLayer {
+    /// Creates a new `CompositorLayer`.
+    fn new(pipeline: CompositionPipeline,
+           layer_id: LayerId,
+           bounds: Rect<f32>,
+           page_size: Option<Size2D<f32>>,
+           tile_size: uint,
+           cpu_painting: bool,
+           wants_scroll_events: WantsScrollEventsFlag,
+           scroll_policy: ScrollPolicy)
+           -> CompositorLayer {
         CompositorLayer {
             pipeline: pipeline,
+            id: layer_id,
+            bounds: bounds,
             page_size: page_size,
             scroll_offset: Point2D(0f32, 0f32),
             children: ~[],
             quadtree: match page_size {
-                None => NoTree(tile_size, max_mem),
-                Some(page_size) => Tree(Quadtree::new(Size2D(page_size.width as uint,
-                                                             page_size.height as uint),
-                                                      tile_size,
-                                                      max_mem)),
+                None => NoTree(tile_size, Some(MAX_TILE_MEMORY_PER_LAYER)),
+                Some(page_size) => {
+                    Tree(Quadtree::new(Size2D(page_size.width as uint, page_size.height as uint),
+                                       tile_size,
+                                       Some(MAX_TILE_MEMORY_PER_LAYER)))
+                }
             },
             root_layer: Rc::new(ContainerLayer()),
             hidden: true,
             epoch: Epoch(0),
-            scroll_behavior: Scroll,
+            wants_scroll_events: wants_scroll_events,
+            scroll_policy: scroll_policy,
             cpu_painting: cpu_painting,
             unrendered_color: gfx::color::rgba(0.0, 0.0, 0.0, 0.0),
         }
     }
     
-    /// Constructs a CompositorLayer tree from a frame tree.
-    pub fn from_frame_tree(frame_tree: SendableFrameTree,
-                           tile_size: uint,
-                           max_mem: Option<uint>,
-                           cpu_painting: bool)
-                           -> CompositorLayer {
-        let SendableFrameTree { pipeline, children } = frame_tree;
-        let mut layer = CompositorLayer::new(pipeline, None, tile_size, max_mem, cpu_painting);
-        layer.children = (children.move_iter().map(|child| {
-            let SendableChildFrameTree { frame_tree, rect } = child;
-            let container = Rc::new(ContainerLayer());
-            match rect {
-                Some(rect) => {
-                     container.borrow().scissor.set(Some(rect));
-                     container.borrow().common.with_mut(|common| common.transform = identity().translate(rect.origin.x,
-                                                                                                         rect.origin.y,
-                                                                                                         0f32));
-                }
-                None => {}
-            }
-
-            let child_layer = ~CompositorLayer::from_frame_tree(frame_tree,
-                                                                tile_size,
-                                                                max_mem,
-                                                                cpu_painting);
-            ContainerLayer::add_child_start(container.clone(), ContainerLayerKind(child_layer.root_layer.clone()));
-
-            CompositorLayerChild {
-                child: child_layer,
-                container: container,
-            }
-        })).collect();
-        layer.set_occlusions();
-        layer
+    /// Creates a new root `CompositorLayer` bound to a composition pipeline with an optional page
+    /// size. If no page size is given, the layer is initially hidden and initialized without a
+    /// quadtree.
+    pub fn new_root(pipeline: CompositionPipeline,
+                    page_size: Size2D<f32>,
+                    tile_size: uint,
+                    cpu_painting: bool)
+                    -> CompositorLayer {
+        CompositorLayer {
+            pipeline: pipeline,
+            id: LayerId::null(),
+            bounds: Rect(Point2D(0f32, 0f32), page_size),
+            page_size: Some(page_size),
+            scroll_offset: Point2D(0f32, 0f32),
+            children: ~[],
+            quadtree: NoTree(tile_size, Some(MAX_TILE_MEMORY_PER_LAYER)),
+            root_layer: Rc::new(ContainerLayer()),
+            hidden: false,
+            epoch: Epoch(0),
+            wants_scroll_events: WantsScrollEvents,
+            scroll_policy: FixedPosition,
+            cpu_painting: cpu_painting,
+            unrendered_color: gfx::color::rgba(0.0, 0.0, 0.0, 0.0),
+        }
     }
 
-    // Move the layer by as relative specified amount in page coordinates. Does not change
-    // the position of the layer relative to its parent. This also takes in a cursor position
-    // to see if the mouse is over child layers first. If a layer successfully scrolled, returns
-    // true; otherwise returns false, so a parent layer can scroll instead.
-    pub fn scroll(&mut self, delta: Point2D<f32>, cursor: Point2D<f32>, window_size: Size2D<f32>)
-                  -> bool {
+    /// Adds a child layer to the layer with the given ID and the given pipeline, if it doesn't
+    /// exist yet. The child layer will have the same pipeline, tile size, memory limit, and CPU
+    /// painting status as its parent.
+    ///
+    /// Returns:
+    ///   * True if the layer was added;
+    ///   * True if the layer was not added because it already existed;
+    ///   * False if the layer could not be added because no suitable parent layer with the given
+    ///     ID and pipeline could be found.
+    pub fn add_child_if_necessary(&mut self,
+                                  container_layer: Rc<ContainerLayer>,
+                                  pipeline_id: PipelineId,
+                                  parent_layer_id: LayerId,
+                                  child_layer_id: LayerId,
+                                  rect: Rect<f32>,
+                                  page_size: Size2D<f32>,
+                                  scroll_policy: ScrollPolicy)
+                                  -> bool {
+        if self.pipeline.id != pipeline_id || self.id != parent_layer_id {
+            return self.children.mut_iter().any(|kid_holder| {
+                kid_holder.child.add_child_if_necessary(kid_holder.container.clone(),
+                                                        pipeline_id,
+                                                        parent_layer_id,
+                                                        child_layer_id,
+                                                        rect,
+                                                        page_size,
+                                                        scroll_policy)
+            })
+        }
+
+        // See if we've already made this child layer.
+        if self.children.iter().any(|kid_holder| {
+                    kid_holder.child.pipeline.id == pipeline_id &&
+                    kid_holder.child.id == child_layer_id
+                }) {
+            return true
+        }
+
+        let mut kid = ~CompositorLayer::new(self.pipeline.clone(),
+                                            child_layer_id,
+                                            rect,
+                                            Some(page_size),
+                                            self.quadtree.tile_size(),
+                                            self.cpu_painting,
+                                            DoesntWantScrollEvents,
+                                            scroll_policy);
+
+        kid.hidden = false;
+
+        // Place the kid's layer in a container...
+        let kid_container = create_container_layer_from_rect(rect);
+        ContainerLayer::add_child_start(kid_container.clone(),
+                                        ContainerLayerKind(kid.root_layer.clone()));
+
+        // ...and add *that* container as a child of the container passed in.
+        ContainerLayer::add_child_end(container_layer,
+                                      ContainerLayerKind(kid_container.clone()));
+
+        self.children.push(CompositorLayerChild {
+            child: kid,
+            container: kid_container,
+        });
+        true
+    }
+
+    /// Move the layer's descendants that don't want scroll events and scroll by a relative
+    /// specified amount in page coordinates. This also takes in a cursor position to see if the
+    /// mouse is over child layers first. If a layer successfully scrolled, returns true; otherwise
+    /// returns false, so a parent layer can scroll instead.
+    pub fn handle_scroll_event(&mut self,
+                               delta: Point2D<f32>,
+                               cursor: Point2D<f32>,
+                               window_size: Size2D<f32>)
+                               -> bool {
+        // If this layer is hidden, neither it nor its children will scroll.
+        if self.hidden {
+            return false
+        }
+
+        // If this layer doesn't want scroll events, neither it nor its children can handle scroll
+        // events.
+        if self.wants_scroll_events != WantsScrollEvents {
+            return false
+        }
+
+        // Allow children to scroll.
         let cursor = cursor - self.scroll_offset;
-        for child in self.children.mut_iter().filter(|x| !x.child.hidden) {
+        for child in self.children.mut_iter() {
             // NOTE: work around borrowchk
             let tmp = child.container.borrow().scissor.borrow();
             match *tmp.get() {
@@ -206,42 +314,82 @@ impl CompositorLayer {
                 Some(rect) => {
                     if cursor.x >= rect.origin.x && cursor.x < rect.origin.x + rect.size.width
                         && cursor.y >= rect.origin.y && cursor.y < rect.origin.y + rect.size.height
-                        && child.child.scroll(delta, cursor - rect.origin, rect.size) {
-                        return true;
+                        && child.child.handle_scroll_event(delta,
+                                                           cursor - rect.origin,
+                                                           rect.size) {
+                        return true
                     }
                 }
             }
         }
 
         // This scroll event is mine!
-        match self.scroll_behavior {
-            Scroll => {
-                // Scroll this layer!
-                let old_origin = self.scroll_offset;
-                self.scroll_offset = self.scroll_offset + delta;
+        // Scroll this layer!
+        let old_origin = self.scroll_offset;
+        self.scroll_offset = self.scroll_offset + delta;
 
-                // bounds checking
-                let page_size = match self.page_size {
-                    Some(size) => size,
-                    None => fail!("CompositorLayer: tried to scroll with no page size set"),
-                };
-                let min_x = cmp::min(window_size.width - page_size.width, 0.0);
-                self.scroll_offset.x = self.scroll_offset.x.clamp(&min_x, &0.0);
-                let min_y = cmp::min(window_size.height - page_size.height, 0.0);
-                self.scroll_offset.y = self.scroll_offset.y.clamp(&min_y, &0.0);
+        // bounds checking
+        let page_size = match self.page_size {
+            Some(size) => size,
+            None => fail!("CompositorLayer: tried to scroll with no page size set"),
+        };
+        let min_x = cmp::min(window_size.width - page_size.width, 0.0);
+        self.scroll_offset.x = self.scroll_offset.x.clamp(&min_x, &0.0);
+        let min_y = cmp::min(window_size.height - page_size.height, 0.0);
+        self.scroll_offset.y = self.scroll_offset.y.clamp(&min_y, &0.0);
 
-                // check to see if we scrolled
-                if old_origin - self.scroll_offset == Point2D(0f32, 0f32) {
-                    return false;
-                }
-
-                self.root_layer.borrow().common.with_mut(|common| common.set_transform(identity().translate(self.scroll_offset.x,
-                                                                                                            self.scroll_offset.y,
-                                                                                                            0.0)));
-                true
-            }
-            FixedPosition => false, // Ignore this scroll event.
+        if old_origin - self.scroll_offset == Point2D(0f32, 0f32) {
+            return false
         }
+
+        self.scroll(self.scroll_offset)
+    }
+
+    #[allow(dead_code)]
+    fn dump_layer_tree(&self, layer: Rc<ContainerLayer>, indent: ~str) {
+        {
+            let scissor = layer.borrow().scissor.borrow();
+            println!("{}scissor {:?}", indent, *scissor.get());
+        }
+        for kid in layer.borrow().children() {
+            match kid {
+                ContainerLayerKind(ref container_layer) => {
+                    self.dump_layer_tree((*container_layer).clone(), indent + "  ");
+                }
+                TextureLayerKind(_) => {
+                    println!("{}  (texture layer)", indent);
+                }
+            }
+        }
+    }
+
+    /// Actually scrolls the descendants of a layer that scroll. This is called by
+    /// `handle_scroll_event` above when it determines that a layer wants to scroll.
+    fn scroll(&mut self, scroll_offset: Point2D<f32>) -> bool {
+        let mut result = false;
+
+        // Only scroll this layer if it's not fixed-positioned.
+        if self.scroll_policy != FixedPosition {
+            // Scroll this layer!
+            self.scroll_offset = scroll_offset;
+
+            self.root_layer
+                .borrow()
+                .common
+                .with_mut(|common| {
+                    common.set_transform(identity().translate(self.scroll_offset.x,
+                                                              self.scroll_offset.y,
+                                                              0.0))
+            });
+
+            result = true
+        }
+
+        for kid_holder in self.children.mut_iter() {
+            result = kid_holder.child.scroll(scroll_offset) || result;
+        }
+
+        result
     }
 
     // Takes in a MouseWindowEvent, determines if it should be passed to children, and 
@@ -282,43 +430,49 @@ impl CompositorLayer {
         chan.try_send(SendEventMsg(self.pipeline.id.clone(), message));
     }
 
-    // Given the current window size, determine which tiles need to be (re)rendered
-    // and sends them off the the appropriate renderer.
-    // Returns a bool that is true if the scene should be repainted.
+    // Given the current window size, determine which tiles need to be (re-)rendered and sends them
+    // off the the appropriate renderer. Returns true if and only if the scene should be repainted.
     pub fn get_buffer_request(&mut self,
                               graphics_context: &NativeCompositingGraphicsContext,
                               window_rect: Rect<f32>,
                               scale: f32)
                               -> bool {
-        let rect = Rect(Point2D(-self.scroll_offset.x + window_rect.origin.x,
-                                -self.scroll_offset.y + window_rect.origin.y),
-                        window_rect.size);
-        let mut redisplay: bool;
-        { // block here to prevent double mutable borrow of self
-            let quadtree = match self.quadtree {
-                NoTree(..) => fail!("CompositorLayer: cannot get buffer request for {:?},
-                                   no quadtree initialized", self.pipeline.id),
-                Tree(ref mut quadtree) => quadtree,
-            };
-            let (request, unused) = quadtree.get_tile_rects_page(rect, scale);
-            redisplay = !unused.is_empty(); // workaround to make redisplay visible outside block
-            if redisplay { // send back unused tiles
-                self.pipeline.render_chan.try_send(UnusedBufferMsg(unused));
+        let mut redisplay = false;
+        match self.quadtree {
+            NoTree(..) => {}
+            Tree(ref mut quadtree) => {
+                let (request, unused) = quadtree.get_tile_rects_page(window_rect, scale);
+
+                // Workaround to make redisplay visible outside block.
+                redisplay = !unused.is_empty();
+                if redisplay {
+                    // Send back unused tiles.
+                    self.pipeline.render_chan.try_send(UnusedBufferMsg(unused));
+                }
+                if !request.is_empty() {
+                    // Ask for tiles.
+                    //
+                    // FIXME(#2003, pcwalton): We may want to batch these up in the case in which
+                    // one page has multiple layers, to avoid the user seeing inconsistent states.
+                    let msg = ReRenderMsg(request, scale, self.id, self.epoch);
+                    self.pipeline.render_chan.try_send(msg);
+                }
             }
-            if !request.is_empty() { // ask for tiles
-                self.pipeline.render_chan.try_send(ReRenderMsg(request, scale, self.epoch));
-            }
-        }
+        };
+
         if redisplay {
             self.build_layer_tree(graphics_context);
         }
+
         let transform = |x: &mut CompositorLayerChild| -> bool {
             // NOTE: work around borrowchk
             let tmp = x.container.borrow().scissor.borrow();
             match *tmp.get() {
                 Some(scissor) => {
-                    let new_rect = rect.intersection(&scissor);
-                    match new_rect {
+                    let mut new_rect = window_rect;
+                    new_rect.origin.x = new_rect.origin.x - x.child.scroll_offset.x;
+                    new_rect.origin.y = new_rect.origin.y - x.child.scroll_offset.y;
+                    match new_rect.intersection(&scissor) {
                         Some(new_rect) => {
                             // Child layers act as if they are rendered at (0,0), so we
                             // subtract the layer's (x,y) coords in its containing page
@@ -328,13 +482,11 @@ impl CompositorLayer {
                             x.child.get_buffer_request(graphics_context, child_rect, scale)
                         }
                         None => {
-                            false //Layer is offscreen
+                            false // Layer is offscreen
                         }
                     }
                 }
-                None => {
-                    fail!("CompositorLayer: Child layer not clipped");
-                }
+                None => fail!("child layer not clipped!"),
             }
         };
         self.children.mut_iter().filter(|x| !x.child.hidden)
@@ -347,9 +499,18 @@ impl CompositorLayer {
     // and clip the layer to the specified size in page coordinates.
     // If the layer is hidden and has a defined page size, unhide it.
     // This method returns false if the specified layer is not found.
-    pub fn set_clipping_rect(&mut self, pipeline_id: PipelineId, new_rect: Rect<f32>) -> bool {
-        match self.children.iter().position(|x| pipeline_id == x.child.pipeline.id) {
+    pub fn set_clipping_rect(&mut self,
+                             pipeline_id: PipelineId,
+                             layer_id: LayerId,
+                             new_rect: Rect<f32>)
+                             -> bool {
+        debug!("compositor_layer: starting set_clipping_rect()");
+        match self.children.iter().position(|kid_holder| {
+                pipeline_id == kid_holder.child.pipeline.id &&
+                layer_id == kid_holder.child.id
+            }) {
             Some(i) => {
+                debug!("compositor_layer: node found for set_clipping_rect()");
                 let child_node = &mut self.children[i];
                 child_node.container.borrow().common.with_mut(|common|
                                                               common.set_transform(identity().translate(new_rect.origin.x,
@@ -360,6 +521,7 @@ impl CompositorLayer {
                     let tmp = child_node.container.borrow().scissor.borrow();
                     tmp.get().clone()
                 };
+
                 child_node.container.borrow().scissor.set(Some(new_rect));
                 match self.quadtree {
                     NoTree(..) => {} // Nothing to do
@@ -382,72 +544,91 @@ impl CompositorLayer {
             None => {
                 // ID does not match any of our immediate children, so recurse on 
                 // descendents (including hidden children)
-                self.children.mut_iter().map(|x| &mut x.child).any(|x| x.set_clipping_rect(pipeline_id, new_rect))
+                self.children
+                    .mut_iter()
+                    .map(|kid_holder| &mut kid_holder.child)
+                    .any(|kid| kid.set_clipping_rect(pipeline_id, layer_id, new_rect))
             }
         }
     }
 
-
     // Set the layer's page size. This signals that the renderer is ready for BufferRequests.
     // If the layer is hidden and has a defined clipping rect, unhide it.
     // This method returns false if the specified layer is not found.
-    pub fn resize(&mut self, pipeline_id: PipelineId, new_size: Size2D<f32>, window_size: Size2D<f32>, epoch: Epoch) -> bool {
-        if self.pipeline.id == pipeline_id {
-            self.epoch = epoch;
-            self.page_size = Some(new_size);
-            match self.quadtree {
-                Tree(ref mut quadtree) => {
-                    self.pipeline.render_chan.try_send(UnusedBufferMsg(quadtree.resize(new_size.width as uint,
-                                                                                       new_size.height as uint)));
-                }
-                NoTree(tile_size, max_mem) => {
-                    self.quadtree = Tree(Quadtree::new(Size2D(new_size.width as uint,
-                                                              new_size.height as uint),
-                                                       tile_size,
-                                                       max_mem))
-                }
-            }
-            // Call scroll for bounds checking if the page shrunk. Use (-1, -1) as the cursor position
-            // to make sure the scroll isn't propagated downwards.
-            self.scroll(Point2D(0f32, 0f32), Point2D(-1f32, -1f32), window_size);
-            self.hidden = false;
-            self.set_occlusions();
-            true
-        } else {
-            self.resize_helper(pipeline_id, new_size, epoch)
+    pub fn resize(&mut self,
+                  pipeline_id: PipelineId,
+                  layer_id: LayerId,
+                  new_size: Size2D<f32>,
+                  window_size: Size2D<f32>,
+                  epoch: Epoch)
+                  -> bool {
+        debug!("compositor_layer: starting resize()");
+        if self.pipeline.id != pipeline_id || self.id != layer_id {
+            return self.resize_helper(pipeline_id, layer_id, new_size, epoch)
         }
+
+        debug!("compositor_layer: layer found for resize()");
+        self.epoch = epoch;
+        self.page_size = Some(new_size);
+        match self.quadtree {
+            Tree(ref mut quadtree) => {
+                self.pipeline
+                    .render_chan
+                    .try_send(UnusedBufferMsg(quadtree.resize(new_size.width as uint,
+                                                              new_size.height as uint)));
+            }
+            NoTree(tile_size, max_mem) => {
+                self.quadtree = Tree(Quadtree::new(Size2D(new_size.width as uint,
+                                                          new_size.height as uint),
+                                                   tile_size,
+                                                   max_mem))
+            }
+        }
+        // Call scroll for bounds checking if the page shrunk. Use (-1, -1) as the cursor position
+        // to make sure the scroll isn't propagated downwards.
+        self.handle_scroll_event(Point2D(0f32, 0f32), Point2D(-1f32, -1f32), window_size);
+        self.hidden = false;
+        self.set_occlusions();
+        true
     }
 
-    pub fn move(&mut self, origin: Point2D<f32>, window_size: Size2D<f32>) -> bool {
-        match self.scroll_behavior {
-            Scroll => {
-                // Scroll this layer!
-                let old_origin = self.scroll_offset;
-                self.scroll_offset = Point2D(0f32, 0f32) - origin;
-
-                // bounds checking
-                let page_size = match self.page_size {
-                    Some(size) => size,
-                    None => fail!("CompositorLayer: tried to scroll with no page size set"),
-                };
-                let min_x = cmp::min(window_size.width - page_size.width, 0.0);
-                self.scroll_offset.x = self.scroll_offset.x.clamp(&min_x, &0.0);
-                let min_y = cmp::min(window_size.height - page_size.height, 0.0);
-                self.scroll_offset.y = self.scroll_offset.y.clamp(&min_y, &0.0);
-
-                // check to see if we scrolled
-                if old_origin - self.scroll_offset == Point2D(0f32, 0f32) {
-                    return false;
-                }
-
-                self.root_layer.borrow().common.with_mut(|common|
-                                                         common.set_transform(identity().translate(self.scroll_offset.x,
-                                                                                                   self.scroll_offset.y,
-                                                                                                   0.0)));
-                true
-            }
-            FixedPosition => false  // Ignore this scroll event.
+    pub fn move(&mut self,
+                pipeline_id: PipelineId,
+                layer_id: LayerId,
+                origin: Point2D<f32>,
+                window_size: Size2D<f32>)
+                -> bool {
+        // Search children for the right layer to move.
+        if self.pipeline.id != pipeline_id || self.id != layer_id {
+            return self.children.mut_iter().any(|kid_holder| {
+                kid_holder.child.move(pipeline_id, layer_id, origin, window_size)
+            })
         }
+
+        if self.wants_scroll_events != WantsScrollEvents {
+            return false
+        }
+
+        // Scroll this layer!
+        let old_origin = self.scroll_offset;
+        self.scroll_offset = Point2D(0f32, 0f32) - origin;
+
+        // bounds checking
+        let page_size = match self.page_size {
+            Some(size) => size,
+            None => fail!("CompositorLayer: tried to scroll with no page size set"),
+        };
+        let min_x = cmp::min(window_size.width - page_size.width, 0.0);
+        self.scroll_offset.x = self.scroll_offset.x.clamp(&min_x, &0.0);
+        let min_y = cmp::min(window_size.height - page_size.height, 0.0);
+        self.scroll_offset.y = self.scroll_offset.y.clamp(&min_y, &0.0);
+
+        // check to see if we scrolled
+        if old_origin - self.scroll_offset == Point2D(0f32, 0f32) {
+            return false;
+        }
+
+        self.scroll(self.scroll_offset)
     }
 
     // Returns whether the layer should be vertically flipped.
@@ -479,9 +660,19 @@ impl CompositorLayer {
     }
     
     // A helper method to resize sublayers.
-    fn resize_helper(&mut self, pipeline_id: PipelineId, new_size: Size2D<f32>, epoch: Epoch) -> bool {
-        let found = match self.children.iter().position(|x| pipeline_id == x.child.pipeline.id) {
+    fn resize_helper(&mut self,
+                     pipeline_id: PipelineId,
+                     layer_id: LayerId,
+                     new_size: Size2D<f32>,
+                     epoch: Epoch)
+                     -> bool {
+        debug!("compositor_layer: starting resize_helper()");
+        let found = match self.children.iter().position(|kid_holder| {
+                pipeline_id == kid_holder.child.pipeline.id &&
+                layer_id == kid_holder.child.id
+            }) {
             Some(i) => {
+                debug!("compositor_layer: layer found for resize_helper()");
                 let child_node = &mut self.children[i];
                 let child = &mut child_node.child;
                 child.epoch = epoch;
@@ -502,9 +693,11 @@ impl CompositorLayer {
                 let tmp = child_node.container.borrow().scissor.borrow();
                 match *tmp.get() {
                     Some(scissor) => {
-                        // Call scroll for bounds checking if the page shrunk. Use (-1, -1) as the cursor position
-                        // to make sure the scroll isn't propagated downwards.
-                        child.scroll(Point2D(0f32, 0f32), Point2D(-1f32, -1f32), scissor.size);
+                        // Call scroll for bounds checking if the page shrunk. Use (-1, -1) as the
+                        // cursor position to make sure the scroll isn't propagated downwards.
+                        child.handle_scroll_event(Point2D(0f32, 0f32),
+                                                  Point2D(-1f32, -1f32),
+                                                  scissor.size);
                         child.hidden = false;
                     }
                     None => {} // Nothing to do
@@ -516,11 +709,15 @@ impl CompositorLayer {
                 
         if found { // Boolean flag to get around double borrow of self
             self.set_occlusions();
-            true
-        } else {
-            // ID does not match ours, so recurse on descendents (including hidden children)
-            self.children.mut_iter().map(|x| &mut x.child).any(|x| x.resize_helper(pipeline_id, new_size, epoch))
+            return true
         }
+
+        // If we got here, the layer's ID does not match ours, so recurse on descendents (including
+        // hidden children).
+        self.children
+            .mut_iter()
+            .map(|kid_holder| &mut kid_holder.child)
+            .any(|kid_holder| kid_holder.resize_helper(pipeline_id, layer_id, new_size, epoch))
     }
 
     // Collect buffers from the quadtree. This method IS NOT recursive, so child CompositorLayers
@@ -577,7 +774,9 @@ impl CompositorLayer {
                     buffer.native_surface.bind_to_texture(graphics_context, &texture, size);
 
                     // Make a texture layer and add it.
-                    texture_layer = Rc::new(TextureLayer::new(texture, buffer.screen_pos.size, flip));
+                    texture_layer = Rc::new(TextureLayer::new(texture,
+                                                              buffer.screen_pos.size,
+                                                              flip));
                     ContainerLayer::add_child_end(self.root_layer.clone(),
                                                   TextureLayerKind(texture_layer.clone()));
                     None
@@ -632,57 +831,65 @@ impl CompositorLayer {
     pub fn add_buffers(&mut self,
                        graphics_context: &NativeCompositingGraphicsContext,
                        pipeline_id: PipelineId,
+                       layer_id: LayerId,
                        mut new_buffers: ~LayerBufferSet,
                        epoch: Epoch)
                        -> Option<~LayerBufferSet> {
-        if self.pipeline.id == pipeline_id {
-            if self.epoch != epoch {
-                debug!("compositor epoch mismatch: {:?} != {:?}, id: {:?}",
-                       self.epoch,
-                       epoch,
-                       self.pipeline.id);
-                self.pipeline.render_chan.try_send(UnusedBufferMsg(new_buffers.buffers));
-                return None;
+        debug!("compositor_layer: starting add_buffers()");
+        if self.pipeline.id != pipeline_id || self.id != layer_id {
+            // ID does not match ours, so recurse on descendents (including hidden children).
+            for child_layer in self.children.mut_iter() {
+                match child_layer.child.add_buffers(graphics_context,
+                                                    pipeline_id,
+                                                    layer_id,
+                                                    new_buffers,
+                                                    epoch) {
+                    None => return None,
+                    Some(buffers) => new_buffers = buffers,
+                }
             }
 
-            {
-                // Block here to prevent double mutable borrow of self.
-                let quadtree = match self.quadtree {
-                    NoTree(..) => fail!("CompositorLayer: cannot add buffers, no quadtree initialized"),
-                    Tree(ref mut quadtree) => quadtree,
-                };
-                
-                let mut unused_tiles = ~[];
-                // move_rev_iter is more efficient
-                for buffer in new_buffers.buffers.move_rev_iter() {
-                    unused_tiles.push_all_move(quadtree.add_tile_pixel(buffer.screen_pos.origin.x,
-                                                                       buffer.screen_pos.origin.y,
-                                                                       buffer.resolution, buffer));
-                }
-                if !unused_tiles.is_empty() { // send back unused buffers
-                    self.pipeline.render_chan.try_send(UnusedBufferMsg(unused_tiles));
-                }
-            }
-            self.build_layer_tree(graphics_context);
-            return None;
+            // Not found. Give the caller the buffers back.
+            return Some(new_buffers)
         }
 
-        // ID does not match ours, so recurse on descendents (including hidden children).
-        for child_layer in self.children.mut_iter() {
-            match child_layer.child.add_buffers(graphics_context,
-                                                pipeline_id,
-                                                new_buffers,
-                                                epoch) {
-                None => return None,
-                Some(buffers) => new_buffers = buffers,
+        debug!("compositor_layer: layers found for add_buffers()");
+
+        if self.epoch != epoch {
+            debug!("add_buffers: compositor epoch mismatch: {:?} != {:?}, id: {:?}",
+                   self.epoch,
+                   epoch,
+                   self.pipeline.id);
+            self.pipeline.render_chan.try_send(UnusedBufferMsg(new_buffers.buffers));
+            return None
+        }
+
+        {
+            let quadtree = match self.quadtree {
+                NoTree(..) => {
+                    fail!("CompositorLayer: cannot add buffers, no quadtree initialized")
+                }
+                Tree(ref mut quadtree) => quadtree,
+            };
+
+            let mut unused_tiles = ~[];
+            for buffer in new_buffers.buffers.move_rev_iter() {
+                unused_tiles.push_all_move(quadtree.add_tile_pixel(buffer.screen_pos.origin.x,
+                                                                   buffer.screen_pos.origin.y,
+                                                                   buffer.resolution,
+                                                                   buffer));
+            }
+            if !unused_tiles.is_empty() { // send back unused buffers
+                self.pipeline.render_chan.try_send(UnusedBufferMsg(unused_tiles));
             }
         }
 
-        // Not found. Give the caller the buffers back.
-        Some(new_buffers)
+        self.build_layer_tree(graphics_context);
+        return None
     }
 
-    // Deletes a specified sublayer, including hidden children. Returns false if the layer is not found.
+    // Deletes a specified sublayer, including hidden children. Returns false if the layer is not
+    // found.
     pub fn delete(&mut self,
                   graphics_context: &NativeCompositingGraphicsContext,
                   pipeline_id: PipelineId)
@@ -717,8 +924,11 @@ impl CompositorLayer {
         }
     }
 
-    pub fn invalidate_rect(&mut self, pipeline_id: PipelineId, rect: Rect<f32>) -> bool {
-        if self.pipeline.id == pipeline_id {
+    pub fn invalidate_rect(&mut self, pipeline_id: PipelineId, layer_id: LayerId, rect: Rect<f32>)
+                           -> bool {
+        debug!("compositor_layer: starting invalidate_rect()");
+        if self.pipeline.id == pipeline_id && layer_id == self.id {
+            debug!("compositor_layer: layer found for invalidate_rect()");
             let quadtree = match self.quadtree {
                 NoTree(..) => return true, // Nothing to do
                 Tree(ref mut quadtree) => quadtree,
@@ -727,7 +937,10 @@ impl CompositorLayer {
             true
         } else {
             // ID does not match ours, so recurse on descendents (including hidden children).
-            self.children.mut_iter().map(|x| &mut x.child).any(|x| x.invalidate_rect(pipeline_id, rect))
+            self.children
+                .mut_iter()
+                .map(|kid_holder| &mut kid_holder.child)
+                .any(|kid| kid.invalidate_rect(pipeline_id, layer_id, rect))
         }
     }
     
@@ -773,16 +986,6 @@ impl CompositorLayer {
         }
     }
 
-    /// Destroys all quadtree tiles of all layers, including child layers, sending the buffers
-    /// back to the renderer to be destroyed or reused.
-    pub fn clear_all(&mut self) {
-        self.clear();
-
-        for kid in self.children.mut_iter() {
-            kid.child.clear_all()
-        }
-    }
-
     /// Destroys all tiles of all layers, including children, *without* sending them back to the
     /// renderer. You must call this only when the render task is destined to be going down;
     /// otherwise, you will leak tiles.
@@ -804,5 +1007,9 @@ impl CompositorLayer {
             kid.child.forget_all_tiles();
         }
     }
+
+    pub fn id_of_first_child(&self) -> LayerId {
+        self.children.iter().next().expect("no first child!").child.id
+    }
 }
 

src/components/main/compositing/compositor_task.rs

@@ -13,8 +13,8 @@ use geom::point::Point2D;
 use geom::rect::Rect;
 use geom::size::Size2D;
 use layers::platform::surface::{NativeCompositingGraphicsContext, NativeGraphicsMetadata};
-use servo_msg::compositor_msg::{Epoch, RenderListener, LayerBufferSet, RenderState, ReadyState};
-use servo_msg::compositor_msg::ScriptListener;
+use servo_msg::compositor_msg::{Epoch, LayerBufferSet, LayerId, LayerMetadata, ReadyState};
+use servo_msg::compositor_msg::{RenderListener, RenderState, ScriptListener, ScrollPolicy};
 use servo_msg::constellation_msg::{ConstellationChan, PipelineId};
 use servo_util::opts::Opts;
 use servo_util::time::ProfilerChan;
@@ -45,12 +45,15 @@ impl ScriptListener for CompositorChan {
         self.chan.send(msg);
     }
 
-    fn invalidate_rect(&self, id: PipelineId, rect: Rect<uint>) {
-        self.chan.send(InvalidateRect(id, rect));
+    fn invalidate_rect(&self, pipeline_id: PipelineId, layer_id: LayerId, rect: Rect<uint>) {
+        self.chan.send(InvalidateRect(pipeline_id, layer_id, rect));
     }
 
-    fn scroll_fragment_point(&self, id: PipelineId, point: Point2D<f32>) {
-	    self.chan.send(ScrollFragmentPoint(id, point));
+    fn scroll_fragment_point(&self,
+                             pipeline_id: PipelineId,
+                             layer_id: LayerId,
+                             point: Point2D<f32>) {
+	    self.chan.send(ScrollFragmentPoint(pipeline_id, layer_id, point));
     }
 
     fn close(&self) {
@@ -72,30 +75,68 @@ impl RenderListener for CompositorChan {
         port.recv()
     }
 
-    fn paint(&self, id: PipelineId, layer_buffer_set: ~LayerBufferSet, epoch: Epoch) {
-        self.chan.send(Paint(id, layer_buffer_set, epoch))
+    fn paint(&self,
+             pipeline_id: PipelineId,
+             layer_id: LayerId,
+             layer_buffer_set: ~LayerBufferSet,
+             epoch: Epoch) {
+        self.chan.send(Paint(pipeline_id, layer_id, layer_buffer_set, epoch))
     }
 
-    fn new_layer(&self, id: PipelineId, page_size: Size2D<uint>) {
+    fn create_layer_group_for_pipeline(&self, id: PipelineId, page_size: Size2D<uint>) {
         let Size2D { width, height } = page_size;
-        self.chan.send(NewLayer(id, Size2D(width as f32, height as f32)))
-    }
-    fn set_layer_page_size_and_color(&self, id: PipelineId, page_size: Size2D<uint>, epoch: Epoch, color: Color) {
-        let Size2D { width, height } = page_size;
-        self.chan.send(SetUnRenderedColor(id, color));
-        self.chan.send(SetLayerPageSize(id, Size2D(width as f32, height as f32), epoch))
+        self.chan.send(CreateRootCompositorLayerIfNecessary(id,
+                                                            LayerId::null(),
+                                                            Size2D(width as f32, height as f32)))
     }
 
-    fn set_layer_clip_rect(&self, id: PipelineId, new_rect: Rect<uint>) {
+    fn initialize_layers_for_pipeline(&self,
+                                      pipeline_id: PipelineId,
+                                      metadata: ~[LayerMetadata],
+                                      epoch: Epoch) {
+        // FIXME(#2004, pcwalton): This assumes that the first layer determines the page size, and
+        // that all other layers are immediate children of it. This is sufficient to handle
+        // `position: fixed` but will not be sufficient to handle `overflow: scroll` or transforms.
+        let mut first = true;
+        for metadata in metadata.iter() {
+            let origin = Point2D(metadata.position.origin.x as f32,
+                                 metadata.position.origin.y as f32);
+            let size = Size2D(metadata.position.size.width as f32,
+                              metadata.position.size.height as f32);
+            let rect = Rect(origin, size);
+            if first {
+                self.chan.send(CreateRootCompositorLayerIfNecessary(pipeline_id,
+                                                                    metadata.id,
+                                                                    size));
+                first = false
+            } else {
+                self.chan
+                    .send(CreateDescendantCompositorLayerIfNecessary(pipeline_id,
+                                                                     metadata.id,
+                                                                     rect,
+                                                                     metadata.scroll_policy));
+            }
+
+            self.chan.send(SetUnRenderedColor(pipeline_id,
+                                              metadata.id,
+                                              metadata.background_color));
+            self.chan.send(SetLayerPageSize(pipeline_id, metadata.id, size, epoch));
+        }
+    }
+
+    fn set_layer_clip_rect(&self,
+                           pipeline_id: PipelineId,
+                           layer_id: LayerId,
+                           new_rect: Rect<uint>) {
         let new_rect = Rect(Point2D(new_rect.origin.x as f32,
                                     new_rect.origin.y as f32),
                             Size2D(new_rect.size.width as f32,
                                    new_rect.size.height as f32));
-        self.chan.send(SetLayerClipRect(id, new_rect))
+        self.chan.send(SetLayerClipRect(pipeline_id, layer_id, new_rect))
     }
 
-    fn delete_layer(&self, id: PipelineId) {
-        self.chan.send(DeleteLayer(id))
+    fn delete_layer_group(&self, id: PipelineId) {
+        self.chan.send(DeleteLayerGroup(id))
     }
 
     fn set_render_state(&self, render_state: RenderState) {
@@ -133,29 +174,32 @@ pub enum Msg {
     /// The headless compositor returns `None`.
     GetGraphicsMetadata(Chan<Option<NativeGraphicsMetadata>>),
 
-    /// Alerts the compositor that there is a new layer to be rendered.
-    NewLayer(PipelineId, Size2D<f32>),
-    /// Alerts the compositor that the specified layer's page has changed size.
-    SetLayerPageSize(PipelineId, Size2D<f32>, Epoch),
+    /// Tells the compositor to create the root layer for a pipeline if necessary (i.e. if no layer
+    /// with that ID exists).
+    CreateRootCompositorLayerIfNecessary(PipelineId, LayerId, Size2D<f32>),
+    /// Tells the compositor to create a descendant layer for a pipeline if necessary (i.e. if no
+    /// layer with that ID exists).
+    CreateDescendantCompositorLayerIfNecessary(PipelineId, LayerId, Rect<f32>, ScrollPolicy),
+    /// Alerts the compositor that the specified layer has changed size.
+    SetLayerPageSize(PipelineId, LayerId, Size2D<f32>, Epoch),
     /// Alerts the compositor that the specified layer's clipping rect has changed.
-    SetLayerClipRect(PipelineId, Rect<f32>),
-    /// Alerts the compositor that the specified layer has been deleted.
-    DeleteLayer(PipelineId),
+    SetLayerClipRect(PipelineId, LayerId, Rect<f32>),
+    /// Alerts the compositor that the specified pipeline has been deleted.
+    DeleteLayerGroup(PipelineId),
     /// Invalidate a rect for a given layer
-    InvalidateRect(PipelineId, Rect<uint>),
+    InvalidateRect(PipelineId, LayerId, Rect<uint>),
     /// Scroll a page in a window
-    ScrollFragmentPoint(PipelineId, Point2D<f32>),
+    ScrollFragmentPoint(PipelineId, LayerId, Point2D<f32>),
     /// Requests that the compositor paint the given layer buffer set for the given page size.
-    Paint(PipelineId, ~LayerBufferSet, Epoch),
+    Paint(PipelineId, LayerId, ~LayerBufferSet, Epoch),
     /// Alerts the compositor to the current status of page loading.
     ChangeReadyState(ReadyState),
     /// Alerts the compositor to the current status of rendering.
     ChangeRenderState(RenderState),
     /// Sets the channel to the current layout and render tasks, along with their id
     SetIds(SendableFrameTree, Chan<()>, ConstellationChan),
-
-    SetUnRenderedColor(PipelineId, Color),
-
+    /// Sets the color of unrendered content for a layer.
+    SetUnRenderedColor(PipelineId, LayerId, Color),
     /// The load of a page for a given URL has completed.
     LoadComplete(PipelineId, Url),
 }

src/components/main/compositing/headless.rs

@@ -77,10 +77,11 @@ impl NullCompositor {
                 // we'll notice and think about whether it needs a response, like
                 // SetIds.
 
-                NewLayer(..) | SetLayerPageSize(..) | SetLayerClipRect(..) | DeleteLayer(..) |
-                Paint(..) | InvalidateRect(..) | ChangeReadyState(..) | ChangeRenderState(..)|
-                ScrollFragmentPoint(..) | SetUnRenderedColor(..) | LoadComplete(..)
-                    => ()
+                CreateRootCompositorLayerIfNecessary(..) |
+                CreateDescendantCompositorLayerIfNecessary(..) | SetLayerPageSize(..) |
+                SetLayerClipRect(..) | DeleteLayerGroup(..) | Paint(..) | InvalidateRect(..) |
+                ChangeReadyState(..) | ChangeRenderState(..) | ScrollFragmentPoint(..) |
+                SetUnRenderedColor(..) | LoadComplete(..) => ()
             }
         }
     }

src/components/main/compositing/quadtree.rs

@@ -460,9 +460,13 @@ impl<T: Tile> QuadtreeNode<T> {
     /// treated as invalid as well.
     /// NOTE: this method will sometimes modify the tree by deleting tiles.
     /// See the QuadTree function description for more details.
-    fn get_tile_rects(&mut self, window: Rect<f32>, clip: Size2D<f32>, scale: f32, tile_size: f32, override: bool) ->
-        (~[BufferRequest], ~[T], int) {
-        
+    fn get_tile_rects(&mut self,
+                      window: Rect<f32>,
+                      clip: Size2D<f32>,
+                      scale: f32,
+                      tile_size: f32,
+                      override: bool)
+                      -> (~[BufferRequest], ~[T], int) {
         let w_x = window.origin.x;
         let w_y = window.origin.y;
         let w_width = window.size.width;
@@ -470,11 +474,11 @@ impl<T: Tile> QuadtreeNode<T> {
         let s_x = self.origin.x;
         let s_y = self.origin.y;
         let s_size = self.size;
-        
+
         // if window is outside of visible region, nothing to do
         if w_x + w_width < s_x || w_x > s_x + s_size
-            || w_y + w_height < s_y || w_y > s_y + s_size 
-            || w_x >= clip.width || w_y >= clip.height {
+                || w_y + w_height < s_y || w_y > s_y + s_size
+                || w_x >= clip.width || w_y >= clip.height {
             return (~[], ~[], 0);
         }
         

src/components/main/constellation.rs

@@ -14,6 +14,7 @@ use script::script_task::{ResizeMsg, ResizeInactiveMsg, ExitPipelineMsg};
 use script::layout_interface;
 use script::layout_interface::LayoutChan;
 use script::script_task::ScriptChan;
+use servo_msg::compositor_msg::LayerId;
 use servo_msg::constellation_msg::{ConstellationChan, ExitMsg, FailureMsg, Failure, FrameRectMsg};
 use servo_msg::constellation_msg::{IFrameSandboxState, IFrameUnsandboxed, InitLoadUrlMsg};
 use servo_msg::constellation_msg::{LoadCompleteMsg, LoadIframeUrlMsg, LoadUrlMsg, Msg, NavigateMsg};
@@ -98,15 +99,6 @@ pub struct SendableChildFrameTree {
     rect: Option<Rect<f32>>,
 }
 
-// impl SendableFrameTree {
-//     fn contains(&self, id: PipelineId) -> bool {
-//         self.pipeline.id == id ||
-//         self.children.iter().any(|&SendableChildFrameTree { frame_tree: ref frame_tree, .. }| {
-//             frame_tree.contains(id)
-//         })
-//     }
-// }
-
 enum ReplaceResult {
     ReplacedNode(Rc<FrameTree>),
     OriginalNode(Rc<FrameTree>),
@@ -511,11 +503,12 @@ impl Constellation {
                 == subpage_id
         };
 
+        let frames = self.find_all(pipeline_id);
+
         {
             // Update a child's frame rect and inform its script task of the change,
             // if it hasn't been already. Optionally inform the compositor if 
             // resize happens immediately.
-            let compositor_chan = self.compositor_chan.clone();
             let update_child_rect = |child_frame_tree: &mut ChildFrameTree, is_active: bool| {
                 child_frame_tree.rect = Some(rect.clone());
                 // NOTE: work around borrowchk issues
@@ -524,21 +517,19 @@ impl Constellation {
                     let Size2D { width, height } = rect.size;
                     if is_active {
                         let pipeline = pipeline.get().borrow();
-                        let ScriptChan(ref chan) = pipeline.script_chan;
-                        chan.send(ResizeMsg(pipeline.id, Size2D {
+                        let ScriptChan(ref script_chan) = pipeline.script_chan;
+                        script_chan.send(ResizeMsg(pipeline.id, Size2D {
                             width:  width  as uint,
                             height: height as uint
                         }));
-                        compositor_chan.send(SetLayerClipRect(pipeline.id, rect));
+                        self.compositor_chan.send(SetLayerClipRect(pipeline.id,
+                                                                   LayerId::null(),
+                                                                   rect));
                     } else {
                         let pipeline = pipeline.get().borrow();
-                        let ScriptChan(ref chan) = pipeline.script_chan;
-                        chan.send(ResizeInactiveMsg(pipeline.id,
-                                                    Size2D(width as uint, height as uint)));
+                        already_sent.insert(pipeline.id);
                     }
-                    let pipeline = pipeline.get().borrow();
-                    already_sent.insert(pipeline.id);
-                }
+                };
             };
 
             // If the subframe is in the current frame tree, the compositor needs the new size
@@ -554,7 +545,6 @@ impl Constellation {
             }
 
             // Update all frames with matching pipeline- and subpage-ids
-            let frames = self.find_all(pipeline_id);
             for frame_tree in frames.iter() {
                 // NOTE: work around borrowchk issues
                 let mut tmp = frame_tree.borrow().children.borrow_mut();

src/components/main/css/node_util.rs

@@ -5,7 +5,7 @@
 use layout::incremental::RestyleDamage;
 use layout::util::LayoutDataAccess;
 use layout::wrapper::{TLayoutNode, ThreadSafeLayoutNode};
-
+use layout::wrapper::{After, AfterBlock, Before, BeforeBlock, Normal};
 use std::cast;
 use style::ComputedValues;
 use sync::Arc;
@@ -25,13 +25,35 @@ impl<'ln> NodeUtil for ThreadSafeLayoutNode<'ln> {
     fn get_css_select_results<'a>(&'a self) -> &'a Arc<ComputedValues> {
         unsafe {
             let layout_data_ref = self.borrow_layout_data();
-            cast::transmute_region(layout_data_ref.get()
-                                                  .as_ref()
-                                                  .unwrap()
-                                                  .data
-                                                  .style
-                                                  .as_ref()
-                                                  .unwrap())
+            match self.get_element_type() {
+                Before | BeforeBlock => {
+                     cast::transmute_region(layout_data_ref.get()
+                                                           .as_ref()
+                                                           .unwrap()
+                                                           .data
+                                                           .before_style
+                                                           .as_ref()
+                                                           .unwrap())
+                }
+                After | AfterBlock => {
+                    cast::transmute_region(layout_data_ref.get()
+                                                          .as_ref()
+                                                          .unwrap()
+                                                          .data
+                                                          .after_style
+                                                          .as_ref()
+                                                          .unwrap())
+                }
+                Normal => {
+                    cast::transmute_region(layout_data_ref.get()
+                                                          .as_ref()
+                                                          .unwrap()
+                                                          .data
+                                                          .style
+                                                          .as_ref()
+                                                          .unwrap())
+                }
+            }
         }
     }
 

src/components/main/layout/box_.rs

@@ -4,17 +4,29 @@
 
 //! The `Box` type, which represents the leaves of the layout tree.
 
+use css::node_style::StyledNode;
+use layout::construct::FlowConstructor;
+use layout::context::LayoutContext;
+use layout::display_list_builder::{DisplayListBuilder, DisplayListBuildingInfo, ToGfxColor};
+use layout::floats::{ClearBoth, ClearLeft, ClearRight, ClearType};
+use layout::flow::{Flow, FlowFlagsInfo};
+use layout::flow;
+use layout::model::{Auto, IntrinsicWidths, MaybeAuto, Specified, specified};
+use layout::model;
+use layout::util::OpaqueNodeMethods;
+use layout::wrapper::{TLayoutNode, ThreadSafeLayoutNode};
+
 use extra::url::Url;
 use sync::{MutexArc, Arc};
 use geom::{Point2D, Rect, Size2D, SideOffsets2D};
 use geom::approxeq::ApproxEq;
 use gfx::color::rgb;
-use gfx::display_list::{BaseDisplayItem, BorderDisplayItem, BorderDisplayItemClass};
-use gfx::display_list::{LineDisplayItem, LineDisplayItemClass};
-use gfx::display_list::{ImageDisplayItem, ImageDisplayItemClass};
-use gfx::display_list::{SolidColorDisplayItem, SolidColorDisplayItemClass, TextDisplayItem};
-use gfx::display_list::{TextDisplayItemClass, TextDisplayItemFlags, ClipDisplayItem};
-use gfx::display_list::{ClipDisplayItemClass, DisplayListCollection};
+use gfx::display_list::{BackgroundAndBorderLevel, BaseDisplayItem, BorderDisplayItem};
+use gfx::display_list::{BorderDisplayItemClass, ClipDisplayItem, ClipDisplayItemClass};
+use gfx::display_list::{DisplayList, ImageDisplayItem, ImageDisplayItemClass, LineDisplayItem};
+use gfx::display_list::{LineDisplayItemClass, OpaqueNode, SolidColorDisplayItem};
+use gfx::display_list::{SolidColorDisplayItemClass, StackingContext, TextDisplayItem};
+use gfx::display_list::{TextDisplayItemClass, TextDisplayItemFlags};
 use gfx::font::FontStyle;
 use gfx::text::text_run::TextRun;
 use servo_msg::constellation_msg::{ConstellationChan, FrameRectMsg, PipelineId, SubpageId};
@@ -24,26 +36,16 @@ use servo_util::geometry::Au;
 use servo_util::geometry;
 use servo_util::range::*;
 use servo_util::namespace;
+use servo_util::smallvec::{SmallVec, SmallVec0};
 use servo_util::str::is_whitespace;
-
 use std::cast;
 use std::cell::RefCell;
 use std::num::Zero;
 use style::{ComputedValues, TElement, TNode, cascade, initial_values};
 use style::computed_values::{LengthOrPercentage, LengthOrPercentageOrAuto, overflow, LPA_Auto};
-use style::computed_values::{border_style, clear, font_family, line_height, position};
-use style::computed_values::{text_align, text_decoration, vertical_align, visibility, white_space};
-
-use css::node_style::StyledNode;
-use layout::construct::FlowConstructor;
-use layout::context::LayoutContext;
-use layout::display_list_builder::{DisplayListBuilder, ExtraDisplayListData, ToGfxColor};
-use layout::floats::{ClearBoth, ClearLeft, ClearRight, ClearType};
-use layout::flow::{Flow, FlowFlagsInfo};
-use layout::flow;
-use layout::model::{MaybeAuto, specified, Auto, Specified};
-use layout::util::OpaqueNode;
-use layout::wrapper::{TLayoutNode, ThreadSafeLayoutNode};
+use style::computed_values::{background_attachment, background_repeat, border_style, clear};
+use style::computed_values::{font_family, line_height, position, text_align, text_decoration};
+use style::computed_values::{vertical_align, visibility, white_space};
 
 /// Boxes (`struct Box`) are the leaves of the layout tree. They cannot position themselves. In
 /// general, boxes do not have a simple correspondence with CSS boxes in the specification:
@@ -288,18 +290,21 @@ pub enum SplitBoxResult {
 }
 
 
-/// data for inline boxes
+/// Data for inline boxes.
+///
+/// FIXME(#2013, pcwalton): Copying `InlineParentInfo` vectors all the time is really inefficient.
+/// Use atomic reference counting instead.
 #[deriving(Clone)]
 pub struct InlineInfo {
-    parent_info: ~[InlineParentInfo],
+    parent_info: SmallVec0<InlineParentInfo>,
     baseline: Au,
 }
 
 impl InlineInfo {
     pub fn new() -> InlineInfo {
         InlineInfo {
-            parent_info: ~[],
-            baseline: Au::new(0),
+            parent_info: SmallVec0::new(),
+            baseline: Au(0),
         }
     }
 }
@@ -414,10 +419,16 @@ def_noncontent_horiz!(left,  merge_noncontent_inline_left,  clear_noncontent_inl
 def_noncontent_horiz!(right, merge_noncontent_inline_right, clear_noncontent_inline_right)
 
 impl Box {
-    /// Constructs a new `Box` instance.
+    /// Constructs a new `Box` instance for the given node.
+    ///
+    /// Arguments:
+    ///
+    ///   * `constructor`: The flow constructor.
+    ///
+    ///   * `node`: The node to create a box for.
     pub fn new(constructor: &mut FlowConstructor, node: &ThreadSafeLayoutNode) -> Box {
         Box {
-            node: OpaqueNode::from_thread_safe_layout_node(node),
+            node: OpaqueNodeMethods::from_thread_safe_layout_node(node),
             style: node.style().clone(),
             border_box: RefCell::new(Au::zero_rect()),
             border: RefCell::new(Zero::zero()),
@@ -433,7 +444,7 @@ impl Box {
     /// Constructs a new `Box` instance from a specific info.
     pub fn new_from_specific_info(node: &ThreadSafeLayoutNode, specific: SpecificBoxInfo) -> Box {
         Box {
-            node: OpaqueNode::from_thread_safe_layout_node(node),
+            node: OpaqueNodeMethods::from_thread_safe_layout_node(node),
             style: node.style().clone(),
             border_box: RefCell::new(Au::zero_rect()),
             border: RefCell::new(Zero::zero()),
@@ -460,7 +471,7 @@ impl Box {
         let (node_style, _) = cascade(&[], false, Some(node.style().get()),
                                       &initial_values(), None);
         Box {
-            node: OpaqueNode::from_thread_safe_layout_node(node),
+            node: OpaqueNodeMethods::from_thread_safe_layout_node(node),
             style: Arc::new(node_style),
             border_box: RefCell::new(Au::zero_rect()),
             border: RefCell::new(Zero::zero()),
@@ -589,54 +600,55 @@ impl Box {
         }
     }
 
-    /// Returns the shared part of the width for computation of minimum and preferred width per
-    /// CSS 2.1.
-    fn guess_width(&self) -> Au {
+    /// Uses the style only to estimate the intrinsic widths. These may be modified for text or
+    /// replaced elements.
+    fn style_specified_intrinsic_width(&self) -> IntrinsicWidths {
+        let (use_margins, use_padding) = match self.specific {
+            GenericBox | IframeBox(_) | ImageBox(_) => (true, true),
+            TableBox | TableCellBox => (false, true),
+            TableWrapperBox => (true, false),
+            TableRowBox => (false, false),
+            ScannedTextBox(_) | TableColumnBox(_) | UnscannedTextBox(_) => {
+                // Styles are irrelevant for these kinds of boxes.
+                return IntrinsicWidths::new()
+            }
+        };
+
         let style = self.style();
-        let mut margin_left = Au::new(0);
-        let mut margin_right = Au::new(0);
-        let mut padding_left = Au::new(0);
-        let mut padding_right = Au::new(0);
-
-        match self.specific {
-            GenericBox | IframeBox(_) | ImageBox(_) => {
-                margin_left = MaybeAuto::from_style(style.Margin.get().margin_left,
-                                                    Au::new(0)).specified_or_zero();
-                margin_right = MaybeAuto::from_style(style.Margin.get().margin_right,
-                                                     Au::new(0)).specified_or_zero();
-                padding_left = self.compute_padding_length(style.Padding.get().padding_left,
-                                                           Au::new(0));
-                padding_right = self.compute_padding_length(style.Padding.get().padding_right,
-                                                            Au::new(0));
-            }
-            TableBox | TableCellBox => {
-                padding_left = self.compute_padding_length(style.Padding.get().padding_left,
-                                                           Au::new(0));
-                padding_right = self.compute_padding_length(style.Padding.get().padding_right,
-                                                            Au::new(0));
-            }
-            TableWrapperBox => {
-                margin_left = MaybeAuto::from_style(style.Margin.get().margin_left,
-                                                    Au::new(0)).specified_or_zero();
-                margin_right = MaybeAuto::from_style(style.Margin.get().margin_right,
-                                                     Au::new(0)).specified_or_zero();
-            }
-            TableRowBox => {}
-            ScannedTextBox(_) | TableColumnBox(_) | UnscannedTextBox(_) => return Au(0),
-        }
-
         let width = MaybeAuto::from_style(style.Box.get().width, Au::new(0)).specified_or_zero();
 
-        width + margin_left + margin_right + padding_left + padding_right +
-            self.border.get().left + self.border.get().right
+        let (margin_left, margin_right) = if use_margins {
+            (MaybeAuto::from_style(style.Margin.get().margin_left, Au(0)).specified_or_zero(),
+             MaybeAuto::from_style(style.Margin.get().margin_right, Au(0)).specified_or_zero())
+        } else {
+            (Au(0), Au(0))
+        };
+
+        let (padding_left, padding_right) = if use_padding {
+            (self.compute_padding_length(style.Padding.get().padding_left, Au(0)),
+             self.compute_padding_length(style.Padding.get().padding_right, Au(0)))
+        } else {
+            (Au(0), Au(0))
+        };
+
+        let surround_width = margin_left + margin_right + padding_left + padding_right +
+                self.border.get().left + self.border.get().right;
+
+        IntrinsicWidths {
+            minimum_width: width,
+            preferred_width: width,
+            surround_width: surround_width,
+        }
     }
 
     pub fn calculate_line_height(&self, font_size: Au) -> Au {
-        match self.line_height() {
+        let from_inline = match self.style().InheritedBox.get().line_height {
             line_height::Normal => font_size.scale_by(1.14),
             line_height::Number(l) => font_size.scale_by(l),
             line_height::Length(l) => l
-        }
+        };
+        let minimum = self.style().InheritedBox.get()._servo_minimum_line_height;
+        Au::max(from_inline, minimum)
     }
 
     /// Populates the box model border parameters from the given computed style.
@@ -864,10 +876,6 @@ impl Box {
         self.style().InheritedText.get().text_align
     }
 
-    pub fn line_height(&self) -> line_height::T {
-        self.style().InheritedBox.get().line_height
-    }
-
     pub fn vertical_align(&self) -> vertical_align::T {
         self.style().Box.get().vertical_align
     }
@@ -920,15 +928,6 @@ impl Box {
         }
     }
 
-    /// Returns true if this element is replaced content. This is true for images, form elements,
-    /// and so on.
-    pub fn is_replaced(&self) -> bool {
-        match self.specific {
-            ImageBox(..) => true,
-            _ => false,
-        }
-    }
-
     /// Returns true if this element can be split. This is true for text boxes.
     pub fn can_split(&self) -> bool {
         match self.specific {
@@ -951,12 +950,10 @@ impl Box {
         (Au::new(0), Au::new(0))
     }
 
-    pub fn paint_inline_background_border_if_applicable<E:ExtraDisplayListData>(
-                                          &self,
-                                          index: uint,
-                                          lists: &RefCell<DisplayListCollection<E>>,
-                                          absolute_bounds: &Rect<Au>,
-                                          offset: &Point2D<Au>) {
+    pub fn paint_inline_background_border_if_applicable(&self,
+                                                        list: &mut DisplayList,
+                                                        absolute_bounds: &Rect<Au>,
+                                                        offset: &Point2D<Au>) {
         // FIXME: This causes a lot of background colors to be displayed when they are clearly not
         // needed. We could use display list optimization to clean this up, but it still seems
         // inefficient. What we really want is something like "nearest ancestor element that
@@ -965,7 +962,7 @@ impl Box {
         match info.get() {
             &Some(ref box_info) => {
                 let mut bg_rect = absolute_bounds.clone();
-                for info in box_info.parent_info.rev_iter() {
+                for info in box_info.parent_info.as_slice().rev_iter() {
                     // TODO (ksh8281) compute vertical-align, line-height
                     bg_rect.origin.y = box_info.baseline + offset.y - info.font_ascent;
                     bg_rect.size.height = info.font_ascent + info.font_descent;
@@ -973,23 +970,24 @@ impl Box {
                         info.style.get().Background.get().background_color);
 
                     if !background_color.alpha.approx_eq(&0.0) {
-                        lists.with_mut(|lists| {
-                            let solid_color_display_item = ~SolidColorDisplayItem {
-                                base: BaseDisplayItem {
-                                          bounds: bg_rect.clone(),
-                                          extra: ExtraDisplayListData::new(self),
-                                      },
-                                      color: background_color.to_gfx_color(),
-                            };
+                        let solid_color_display_item = ~SolidColorDisplayItem {
+                            base: BaseDisplayItem {
+                                      bounds: bg_rect.clone(),
+                                      node: self.node,
+                                  },
+                                  color: background_color.to_gfx_color(),
+                        };
 
-                            lists.lists[index].append_item(SolidColorDisplayItemClass(solid_color_display_item))
-                        });
+                        list.push(SolidColorDisplayItemClass(solid_color_display_item))
                     }
+
                     let border = &info.border;
+
                     // Fast path.
                     if border.is_zero() {
-                        continue;
+                        continue
                     }
+
                     bg_rect.origin.y = bg_rect.origin.y - border.top;
                     bg_rect.size.height = bg_rect.size.height + border.top + border.bottom;
 
@@ -1003,26 +1001,20 @@ impl Box {
                     let bottom_style = style.Border.get().border_bottom_style;
                     let left_style = style.Border.get().border_left_style;
 
+                    let border_display_item = ~BorderDisplayItem {
+                        base: BaseDisplayItem {
+                            bounds: bg_rect,
+                            node: self.node,
+                        },
+                        border: border.clone(),
+                        color: SideOffsets2D::new(top_color.to_gfx_color(),
+                        right_color.to_gfx_color(),
+                        bottom_color.to_gfx_color(),
+                        left_color.to_gfx_color()),
+                        style: SideOffsets2D::new(top_style, right_style, bottom_style, left_style)
+                    };
 
-                    lists.with_mut(|lists| {
-                        let border_display_item = ~BorderDisplayItem {
-                            base: BaseDisplayItem {
-                                      bounds: bg_rect,
-                                      extra: ExtraDisplayListData::new(self),
-                                  },
-                                  border: border.clone(),
-                                  color: SideOffsets2D::new(top_color.to_gfx_color(),
-                                  right_color.to_gfx_color(),
-                                  bottom_color.to_gfx_color(),
-                                  left_color.to_gfx_color()),
-                                  style: SideOffsets2D::new(top_style,
-                                  right_style,
-                                  bottom_style,
-                                  left_style)
-                        };
-
-                        lists.lists[index].append_item(BorderDisplayItemClass(border_display_item))
-                    });
+                    list.push(BorderDisplayItemClass(border_display_item));
 
                     bg_rect.origin.x = bg_rect.origin.x + border.left;
                     bg_rect.size.width = bg_rect.size.width - border.left - border.right;
@@ -1033,11 +1025,9 @@ impl Box {
     }
     /// Adds the display items necessary to paint the background of this box to the display list if
     /// necessary.
-    pub fn paint_background_if_applicable<E:ExtraDisplayListData>(
-                                          &self,
+    pub fn paint_background_if_applicable(&self,
+                                          list: &mut DisplayList,
                                           builder: &DisplayListBuilder,
-                                          index: uint,
-                                          lists: &RefCell<DisplayListCollection<E>>,
                                           absolute_bounds: &Rect<Au>) {
         // FIXME: This causes a lot of background colors to be displayed when they are clearly not
         // needed. We could use display list optimization to clean this up, but it still seems
@@ -1046,17 +1036,15 @@ impl Box {
         let style = self.style();
         let background_color = style.resolve_color(style.Background.get().background_color);
         if !background_color.alpha.approx_eq(&0.0) {
-            lists.with_mut(|lists| {
-                let solid_color_display_item = ~SolidColorDisplayItem {
-                    base: BaseDisplayItem {
-                        bounds: *absolute_bounds,
-                        extra: ExtraDisplayListData::new(self),
-                    },
-                    color: background_color.to_gfx_color(),
-                };
+            let display_item = ~SolidColorDisplayItem {
+                base: BaseDisplayItem {
+                    bounds: *absolute_bounds,
+                    node: self.node,
+                },
+                color: background_color.to_gfx_color(),
+            };
 
-                lists.lists[index].append_item(SolidColorDisplayItemClass(solid_color_display_item))
-            });
+            list.push(SolidColorDisplayItemClass(display_item))
         }
 
         // The background image is painted on top of the background color.
@@ -1064,22 +1052,81 @@ impl Box {
         // http://www.w3.org/TR/CSS21/colors.html#background
         match style.Background.get().background_image {
             Some(ref image_url) => {
-                let mut holder = ImageHolder::new(image_url.clone(), builder.ctx.image_cache.clone());
+                let mut holder = ImageHolder::new(image_url.clone(),
+                                                  builder.ctx.image_cache.clone());
                 match holder.get_image() {
                     Some(image) => {
                         debug!("(building display list) building background image");
 
-                        // Place the image into the display list.
-                        lists.with_mut(|lists| {
-                            let image_display_item = ~ImageDisplayItem {
-                                base: BaseDisplayItem {
-                                    bounds: *absolute_bounds,
-                                    extra: ExtraDisplayListData::new(self),
-                                },
-                                image: image.clone(),
-                            };
-                            lists.lists[index].append_item(ImageDisplayItemClass(image_display_item));
+                        // Adjust bounds for `background-position` and `background-attachment`.
+                        let mut bounds = *absolute_bounds;
+                        let horizontal_position = model::specified(
+                            style.Background.get().background_position.horizontal,
+                            bounds.size.width);
+                        let vertical_position = model::specified(
+                            style.Background.get().background_position.vertical,
+                            bounds.size.height);
+
+                        let clip_display_item;
+                        match style.Background.get().background_attachment {
+                            background_attachment::scroll => {
+                                clip_display_item = None;
+                                bounds.origin.x = bounds.origin.x + horizontal_position;
+                                bounds.origin.y = bounds.origin.y + vertical_position;
+                                bounds.size.width = bounds.size.width - horizontal_position;
+                                bounds.size.height = bounds.size.height - vertical_position;
+                            }
+                            background_attachment::fixed => {
+                                clip_display_item = Some(~ClipDisplayItem {
+                                    base: BaseDisplayItem {
+                                        bounds: bounds,
+                                        node: self.node,
+                                    },
+                                    child_list: SmallVec0::new(),
+                                    need_clip: true,
+                                });
+
+                                bounds = Rect {
+                                    origin: Point2D(horizontal_position, vertical_position),
+                                    size: Size2D(bounds.origin.x + bounds.size.width,
+                                                 bounds.origin.y + bounds.size.height),
+                                }
+                            }
+                        }
+                        // Adjust sizes for `background-repeat`.
+                        match style.Background.get().background_repeat {
+                            background_repeat::no_repeat => {
+                                bounds.size.width = Au::from_px(image.get().width as int);
+                                bounds.size.height = Au::from_px(image.get().height as int)
+                            }
+                            background_repeat::repeat_x => {
+                                bounds.size.height = Au::from_px(image.get().height as int)
+                            }
+                            background_repeat::repeat_y => {
+                                bounds.size.width = Au::from_px(image.get().width as int)
+                            }
+                            background_repeat::repeat => {}
+                        };
+
+
+                        // Create the image display item.
+                        let image_display_item = ImageDisplayItemClass(~ImageDisplayItem {
+                            base: BaseDisplayItem {
+                                bounds: bounds,
+                                node: self.node,
+                            },
+                            image: image.clone(),
+                            stretch_size: Size2D(Au::from_px(image.get().width as int),
+                                                 Au::from_px(image.get().height as int)),
                         });
+
+                        match clip_display_item {
+                            None => list.push(image_display_item),
+                            Some(mut clip_display_item) => {
+                                clip_display_item.child_list.push(image_display_item);
+                                list.push(ClipDisplayItemClass(clip_display_item))
+                            }
+                        }
                     }
                     None => {
                         // No image data at all? Do nothing.
@@ -1095,11 +1142,7 @@ impl Box {
 
     /// Adds the display items necessary to paint the borders of this box to a display list if
     /// necessary.
-    pub fn paint_borders_if_applicable<E:ExtraDisplayListData>(
-                                       &self,
-                                       index: uint,
-                                       lists: &RefCell<DisplayListCollection<E>>,
-                                       abs_bounds: &Rect<Au>) {
+    pub fn paint_borders_if_applicable(&self, list: &mut DisplayList, abs_bounds: &Rect<Au>) {
         // Fast path.
         let border = self.border.get();
         if border.is_zero() {
@@ -1122,75 +1165,142 @@ impl Box {
             - self.noncontent_inline_right();
 
         // Append the border to the display list.
-        lists.with_mut(|lists| {
-            let border_display_item = ~BorderDisplayItem {
-                base: BaseDisplayItem {
-                    bounds: abs_bounds,
-                    extra: ExtraDisplayListData::new(self),
-                },
-                border: border,
-                color: SideOffsets2D::new(top_color.to_gfx_color(),
-                                          right_color.to_gfx_color(),
-                                          bottom_color.to_gfx_color(),
-                                          left_color.to_gfx_color()),
-                style: SideOffsets2D::new(top_style,
-                                          right_style,
-                                          bottom_style,
-                                          left_style)
-            };
+        let border_display_item = ~BorderDisplayItem {
+            base: BaseDisplayItem {
+                bounds: abs_bounds,
+                node: self.node,
+            },
+            border: border,
+            color: SideOffsets2D::new(top_color.to_gfx_color(),
+                                      right_color.to_gfx_color(),
+                                      bottom_color.to_gfx_color(),
+                                      left_color.to_gfx_color()),
+            style: SideOffsets2D::new(top_style,
+                                      right_style,
+                                      bottom_style,
+                                      left_style)
+        };
 
-            lists.lists[index].append_item(BorderDisplayItemClass(border_display_item))
-        });
+        list.push(BorderDisplayItemClass(border_display_item))
     }
 
-    /// Adds the display items for this box to the given display list.
+    fn build_debug_borders_around_text_boxes(&self,
+                                             stacking_context: &mut StackingContext,
+                                             flow_origin: Point2D<Au>,
+                                             text_box: &ScannedTextBoxInfo) {
+        let box_bounds = self.border_box.get();
+        let absolute_box_bounds = box_bounds.translate(&flow_origin);
+
+        // Compute the text box bounds and draw a border surrounding them.
+        let debug_border = SideOffsets2D::new_all_same(Au::from_px(1));
+
+        let border_display_item = ~BorderDisplayItem {
+            base: BaseDisplayItem {
+                bounds: absolute_box_bounds,
+                node: self.node,
+            },
+            border: debug_border,
+            color: SideOffsets2D::new_all_same(rgb(0, 0, 200)),
+            style: SideOffsets2D::new_all_same(border_style::solid)
+
+        };
+        stacking_context.content.push(BorderDisplayItemClass(border_display_item));
+
+        // Draw a rectangle representing the baselines.
+        let ascent = text_box.run.get().metrics_for_range(&text_box.range).ascent;
+        let baseline = Rect(absolute_box_bounds.origin + Point2D(Au(0), ascent),
+                            Size2D(absolute_box_bounds.size.width, Au(0)));
+
+        let line_display_item = ~LineDisplayItem {
+            base: BaseDisplayItem {
+                bounds: baseline,
+                node: self.node,
+            },
+            color: rgb(0, 200, 0),
+            style: border_style::dashed,
+
+        };
+        stacking_context.content.push(LineDisplayItemClass(line_display_item))
+    }
+
+    fn build_debug_borders_around_box(&self,
+                                      stacking_context: &mut StackingContext,
+                                      flow_origin: Point2D<Au>) {
+        let box_bounds = self.border_box.get();
+        let absolute_box_bounds = box_bounds.translate(&flow_origin);
+
+        // This prints a debug border around the border of this box.
+        let debug_border = SideOffsets2D::new_all_same(Au::from_px(1));
+
+        let border_display_item = ~BorderDisplayItem {
+            base: BaseDisplayItem {
+                bounds: absolute_box_bounds,
+                node: self.node,
+            },
+            border: debug_border,
+            color: SideOffsets2D::new_all_same(rgb(0, 0, 200)),
+            style: SideOffsets2D::new_all_same(border_style::solid)
+
+        };
+        stacking_context.content.push(BorderDisplayItemClass(border_display_item))
+    }
+
+    /// Adds the display items for this box to the given stacking context.
     ///
     /// Arguments:
+    ///
+    /// * `stacking_context`: The stacking context to add display items to.
     /// * `builder`: The display list builder, which manages the coordinate system and options.
     /// * `dirty`: The dirty rectangle in the coordinate system of the owning flow.
     /// * `flow_origin`: Position of the origin of the owning flow wrt the display list root flow.
     ///   box.
-    /// * `list`: The display list to which items should be appended.
-    ///
-    /// TODO: To implement stacking contexts correctly, we need to create a set of display lists,
-    /// one per layer of the stacking context (CSS 2.1 § 9.9.1). Each box is passed the list set
-    /// representing the box's stacking context. When asked to construct its constituent display
-    /// items, each box puts its display items into the correct stack layer according to CSS 2.1
-    /// Appendix E. Finally, the builder flattens the list.
-    pub fn build_display_list<E:ExtraDisplayListData>(
-                              &self,
+    /// * `flow`: The flow that this box belongs to.
+    pub fn build_display_list(&self,
+                              stacking_context: &mut StackingContext,
                               builder: &DisplayListBuilder,
-                              dirty: &Rect<Au>,
+                              _: &DisplayListBuildingInfo,
                               flow_origin: Point2D<Au>,
                               flow: &Flow,
-                              index: uint,
-                              lists: &RefCell<DisplayListCollection<E>>) {
+                              background_and_border_level: BackgroundAndBorderLevel) {
         // Box position wrt to the owning flow.
         let box_bounds = self.border_box.get();
         let absolute_box_bounds = box_bounds.translate(&flow_origin);
         debug!("Box::build_display_list at rel={}, abs={}: {:s}",
-               box_bounds, absolute_box_bounds, self.debug_str());
-        debug!("Box::build_display_list: dirty={}, flow_origin={}", *dirty, flow_origin);
+               box_bounds,
+               absolute_box_bounds,
+               self.debug_str());
+        debug!("Box::build_display_list: dirty={}, flow_origin={}", builder.dirty, flow_origin);
 
         if self.style().InheritedBox.get().visibility != visibility::visible {
-            return;
+            return
         }
 
-        if absolute_box_bounds.intersects(dirty) {
-            debug!("Box::build_display_list: intersected. Adding display item...");
-        } else {
+        if !absolute_box_bounds.intersects(&builder.dirty) {
             debug!("Box::build_display_list: Did not intersect...");
-            return;
+            return
         }
 
-        self.paint_inline_background_border_if_applicable(index, lists, &absolute_box_bounds, &flow_origin);
-        // Add the background to the list, if applicable.
-        self.paint_background_if_applicable(builder, index, lists, &absolute_box_bounds);
+        debug!("Box::build_display_list: intersected. Adding display item...");
 
-        // Add a border, if applicable.
-        //
-        // TODO: Outlines.
-        self.paint_borders_if_applicable(index, lists, &absolute_box_bounds);
+        {
+            let list =
+                stacking_context.list_for_background_and_border_level(background_and_border_level);
+
+            // Add a background to the list, if this is an inline.
+            //
+            // FIXME(pcwalton): This is kind of ugly; merge with the call below?
+            self.paint_inline_background_border_if_applicable(list,
+                                                              &absolute_box_bounds,
+                                                              &flow_origin);
+
+            // Add the background to the list, if applicable.
+            self.paint_background_if_applicable(list, builder, &absolute_box_bounds);
+
+            // Add a border, if applicable.
+            //
+            // TODO: Outlines.
+            self.paint_borders_if_applicable(list, &absolute_box_bounds);
+        }
 
         match self.specific {
             UnscannedTextBox(_) => fail!("Shouldn't see unscanned boxes here."),
@@ -1204,7 +1314,7 @@ impl Box {
                 let inline_info = self.inline_info.borrow();
                 match inline_info.get() {
                     &Some(ref info) => {
-                        for data in info.parent_info.rev_iter() {
+                        for data in info.parent_info.as_slice().rev_iter() {
                             let parent_info = FlowFlagsInfo::new(data.style.get());
                             flow_flags.propagate_text_decoration_from_parent(&parent_info);
                         }
@@ -1224,100 +1334,45 @@ impl Box {
                                     - self.noncontent_inline_right();
 
                 // Create the text box.
-                lists.with_mut(|lists| {
-                    let text_display_item = ~TextDisplayItem {
-                        base: BaseDisplayItem {
-                            bounds: bounds,
-                            extra: ExtraDisplayListData::new(self),
-                        },
-                        text_run: text_box.run.clone(),
-                        range: text_box.range,
-                        text_color: text_color,
-                        overline_color: flow_flags.overline_color(text_color),
-                        underline_color: flow_flags.underline_color(text_color),
-                        line_through_color: flow_flags.line_through_color(text_color),
-                        flags: text_flags,
-                    };
+                let text_display_item = ~TextDisplayItem {
+                    base: BaseDisplayItem {
+                        bounds: bounds,
+                        node: self.node,
+                    },
+                    text_run: text_box.run.clone(),
+                    range: text_box.range,
+                    text_color: text_color,
+                    overline_color: flow_flags.overline_color(text_color),
+                    underline_color: flow_flags.underline_color(text_color),
+                    line_through_color: flow_flags.line_through_color(text_color),
+                    flags: text_flags,
+                };
 
-                    lists.lists[index].append_item(TextDisplayItemClass(text_display_item));
-                });
+                stacking_context.content.push(TextDisplayItemClass(text_display_item));
 
                 // Draw debug frames for text bounds.
                 //
                 // FIXME(pcwalton): This is a bit of an abuse of the logging infrastructure. We
                 // should have a real `SERVO_DEBUG` system.
-                debug!("{:?}", {
-                    // Compute the text box bounds and draw a border surrounding them.
-                    let debug_border = SideOffsets2D::new_all_same(Au::from_px(1));
-
-                    lists.with_mut(|lists| {
-                        let border_display_item = ~BorderDisplayItem {
-                            base: BaseDisplayItem {
-                                bounds: absolute_box_bounds,
-                                extra: ExtraDisplayListData::new(self),
-                            },
-                            border: debug_border,
-                            color: SideOffsets2D::new_all_same(rgb(0, 0, 200)),
-                            style: SideOffsets2D::new_all_same(border_style::solid)
-
-                        };
-                        lists.lists[index].append_item(BorderDisplayItemClass(border_display_item));
-                    });
-
-                    // Draw a rectangle representing the baselines.
-                    let ascent = text_box.run.get().metrics_for_range(
-                        &text_box.range).ascent;
-                    let baseline = Rect(absolute_box_bounds.origin + Point2D(Au(0), ascent),
-                                        Size2D(absolute_box_bounds.size.width, Au(0)));
-
-                    lists.with_mut(|lists| {
-                        let line_display_item = ~LineDisplayItem {
-                            base: BaseDisplayItem {
-                                bounds: baseline,
-                                extra: ExtraDisplayListData::new(self),
-                            },
-                            color: rgb(0, 200, 0),
-                            style: border_style::dashed
-
-                        };
-                        lists.lists[index].append_item(LineDisplayItemClass(line_display_item));
-                    });
-                });
+                debug!("{:?}", self.build_debug_borders_around_text_boxes(stacking_context,
+                                                                          flow_origin,
+                                                                          text_box))
             },
             GenericBox | IframeBox(..) | TableBox | TableCellBox | TableRowBox |
             TableWrapperBox => {
-                lists.with_mut(|lists| {
-                    let item = ~ClipDisplayItem {
-                        base: BaseDisplayItem {
-                            bounds: absolute_box_bounds,
-                            extra: ExtraDisplayListData::new(self),
-                        },
-                        child_list: ~[],
-                        need_clip: self.needs_clip()
-                    };
-                    lists.lists[index].append_item(ClipDisplayItemClass(item));
-                });
+                let item = ~ClipDisplayItem {
+                    base: BaseDisplayItem {
+                        bounds: absolute_box_bounds,
+                        node: self.node,
+                    },
+                    child_list: SmallVec0::new(),
+                    need_clip: self.needs_clip()
+                };
+                stacking_context.content.push(ClipDisplayItemClass(item));
 
                 // FIXME(pcwalton): This is a bit of an abuse of the logging infrastructure. We
                 // should have a real `SERVO_DEBUG` system.
-                debug!("{:?}", {
-                    // This prints a debug border around the border of this box.
-                    let debug_border = SideOffsets2D::new_all_same(Au::from_px(1));
-
-                    lists.with_mut(|lists| {
-                        let border_display_item = ~BorderDisplayItem {
-                            base: BaseDisplayItem {
-                                bounds: absolute_box_bounds,
-                                extra: ExtraDisplayListData::new(self),
-                            },
-                            border: debug_border,
-                            color: SideOffsets2D::new_all_same(rgb(0, 0, 200)),
-                            style: SideOffsets2D::new_all_same(border_style::solid)
-
-                        };
-                        lists.lists[index].append_item(BorderDisplayItemClass(border_display_item));
-                    });
-                });
+                debug!("{:?}", self.build_debug_borders_around_box(stacking_context, flow_origin))
             },
             ImageBox(ref image_box) => {
                 let mut image_ref = image_box.image.borrow_mut();
@@ -1335,16 +1390,15 @@ impl Box {
                         debug!("(building display list) building image box");
 
                         // Place the image into the display list.
-                        lists.with_mut(|lists| {
-                            let image_display_item = ~ImageDisplayItem {
-                                base: BaseDisplayItem {
-                                    bounds: bounds,
-                                    extra: ExtraDisplayListData::new(self),
-                                },
-                                image: image.clone(),
-                            };
-                            lists.lists[index].append_item(ImageDisplayItemClass(image_display_item));
-                        });
+                        let image_display_item = ~ImageDisplayItem {
+                            base: BaseDisplayItem {
+                                bounds: bounds,
+                                node: self.node,
+                            },
+                            image: image.clone(),
+                            stretch_size: bounds.size,
+                        };
+                        stacking_context.content.push(ImageDisplayItemClass(image_display_item))
                     }
                     None => {
                         // No image data at all? Do nothing.
@@ -1355,24 +1409,7 @@ impl Box {
                 }
                 // FIXME(pcwalton): This is a bit of an abuse of the logging infrastructure. We
                 // should have a real `SERVO_DEBUG` system.
-                debug!("{:?}", {
-                    let debug_border = SideOffsets2D::new_all_same(Au::from_px(1));
-
-                    lists.with_mut(|lists| {
-                        let border_display_item = ~BorderDisplayItem {
-                            base: BaseDisplayItem {
-                                bounds: absolute_box_bounds,
-                                extra: ExtraDisplayListData::new(self),
-                            },
-                            border: debug_border,
-                            color: SideOffsets2D::new_all_same(rgb(0, 0, 200)),
-                            style: SideOffsets2D::new_all_same(border_style::solid)
-
-                        };
-                        lists.lists[index].append_item(BorderDisplayItemClass(border_display_item))
-                    });
-                });
-
+                debug!("{:?}", self.build_debug_borders_around_box(stacking_context, flow_origin))
             }
         }
 
@@ -1392,18 +1429,19 @@ impl Box {
             }
             _ => {}
         }
-
     }
 
-    /// Returns the *minimum width* and *preferred width* of this box as defined by CSS 2.1.
-    pub fn minimum_and_preferred_widths(&self) -> (Au, Au) {
-        let guessed_width = self.guess_width();
-        let (additional_minimum, additional_preferred) = match self.specific {
-            GenericBox | IframeBox(_) | TableBox | TableCellBox | TableColumnBox(_) |
-            TableRowBox | TableWrapperBox => (Au(0), Au(0)),
+    /// Returns the intrinsic widths of this fragment.
+    pub fn intrinsic_widths(&self) -> IntrinsicWidths {
+        let mut result = self.style_specified_intrinsic_width();
+
+        match self.specific {
+            GenericBox | IframeBox(_) | TableBox | TableCellBox | TableColumnBox(_) | TableRowBox |
+            TableWrapperBox => {}
             ImageBox(ref image_box_info) => {
                 let image_width = image_box_info.image_width();
-                (image_width, image_width)
+                result.minimum_width = geometry::max(result.minimum_width, image_width);
+                result.preferred_width = geometry::max(result.preferred_width, image_width);
             }
             ScannedTextBox(ref text_box_info) => {
                 let range = &text_box_info.range;
@@ -1415,11 +1453,29 @@ impl Box {
                     max_line_width = Au::max(max_line_width, line_metrics.advance_width);
                 }
 
-                (min_line_width, max_line_width)
+                result.minimum_width = geometry::max(result.minimum_width, min_line_width);
+                result.preferred_width = geometry::max(result.preferred_width, max_line_width);
             }
             UnscannedTextBox(..) => fail!("Unscanned text boxes should have been scanned by now!"),
-        };
-        (guessed_width + additional_minimum, guessed_width + additional_preferred)
+        }
+
+        // Take borders and padding for parent inline boxes into account.
+        let inline_info = self.inline_info.get();
+        match inline_info {
+            None => {}
+            Some(ref inline_info) => {
+                for inline_parent_info in inline_info.parent_info.iter() {
+                    let border_width = inline_parent_info.border.left +
+                        inline_parent_info.border.right;
+                    let padding_width = inline_parent_info.padding.left +
+                        inline_parent_info.padding.right;
+                    result.minimum_width = result.minimum_width + border_width + padding_width;
+                    result.preferred_width = result.preferred_width + border_width + padding_width;
+                }
+            }
+        }
+
+        result
     }
 
 
@@ -1440,8 +1496,8 @@ impl Box {
             UnscannedTextBox(_) => fail!("Unscanned text boxes should have been scanned by now!"),
         }
     }
+
     /// Returns, and computes, the height of this box.
-    ///
     pub fn content_height(&self) -> Au {
         match self.specific {
             GenericBox | IframeBox(_) | TableBox | TableCellBox | TableRowBox |
@@ -1625,16 +1681,16 @@ impl Box {
         }
     }
 
-    /// Assigns replaced width for this box only if it is replaced content.
-    ///
-    /// This assigns only the width, not margin or anything else.
-    /// CSS 2.1 § 10.3.2.
-    pub fn assign_replaced_width_if_necessary(&self,container_width: Au) {
+    /// Assigns replaced width, padding, and margins for this box only if it is replaced content
+    /// per CSS 2.1 § 10.3.2.
+    pub fn assign_replaced_width_if_necessary(&self, container_width: Au) {
         match self.specific {
             GenericBox | IframeBox(_) | TableBox | TableCellBox | TableRowBox |
             TableWrapperBox => {}
             ImageBox(ref image_box_info) => {
-                // TODO(ksh8281): compute border,margin,padding
+                self.compute_padding(self.style(), container_width);
+
+                // TODO(ksh8281): compute border,margin
                 let width = ImageBoxInfo::style_length(self.style().Box.get().width,
                                                        image_box_info.dom_width,
                                                        container_width);

src/components/main/layout/construct.rs

@@ -22,14 +22,14 @@
 
 use css::node_style::StyledNode;
 use layout::block::BlockFlow;
-use layout::box_::{Box, GenericBox, IframeBox, IframeBoxInfo, ImageBox, ImageBoxInfo, TableBox};
-use layout::box_::{TableCellBox, TableColumnBox, TableColumnBoxInfo, TableRowBox, TableWrapperBox};
-use layout::box_::{InlineInfo, InlineParentInfo, SpecificBoxInfo, UnscannedTextBox};
-use layout::box_::{UnscannedTextBoxInfo};
+use layout::box_::{Box, GenericBox, IframeBox, IframeBoxInfo, ImageBox, ImageBoxInfo};
+use layout::box_::{InlineInfo, InlineParentInfo, SpecificBoxInfo};
+use layout::box_::{TableBox, TableCellBox, TableColumnBox, TableColumnBoxInfo, TableRowBox};
+use layout::box_::{TableWrapperBox, UnscannedTextBox, UnscannedTextBoxInfo};
 use layout::context::LayoutContext;
 use layout::floats::FloatKind;
 use layout::flow::{Flow, ImmutableFlowUtils, MutableOwnedFlowUtils};
-use layout::flow::{Descendants, AbsDescendants, FixedDescendants};
+use layout::flow::{Descendants, AbsDescendants};
 use layout::flow_list::{Rawlink};
 use layout::inline::InlineFlow;
 use layout::table_wrapper::TableWrapperFlow;
@@ -40,31 +40,34 @@ use layout::table_rowgroup::TableRowGroupFlow;
 use layout::table_row::TableRowFlow;
 use layout::table_cell::TableCellFlow;
 use layout::text::TextRunScanner;
-use layout::util::{LayoutDataAccess, OpaqueNode};
+use layout::util::{LayoutDataAccess, OpaqueNodeMethods};
 use layout::wrapper::{PostorderNodeMutTraversal, TLayoutNode, ThreadSafeLayoutNode};
+use layout::wrapper::{Before, BeforeBlock, After, AfterBlock, Normal};
 
+use extra::url::Url;
+use gfx::display_list::OpaqueNode;
 use gfx::font_context::FontContext;
 use script::dom::bindings::codegen::InheritTypes::TextCast;
 use script::dom::bindings::js::JS;
-use script::dom::element::{HTMLIFrameElementTypeId, HTMLImageElementTypeId, HTMLObjectElementTypeId};
-use script::dom::element::{HTMLTableElementTypeId, HTMLTableSectionElementTypeId};
-use script::dom::element::{HTMLTableDataCellElementTypeId, HTMLTableHeaderCellElementTypeId};
-use script::dom::element::{HTMLTableColElementTypeId, HTMLTableRowElementTypeId};
+use script::dom::element::{HTMLIFrameElementTypeId, HTMLImageElementTypeId};
+use script::dom::element::{HTMLObjectElementTypeId};
+use script::dom::element::{HTMLTableColElementTypeId, HTMLTableDataCellElementTypeId};
+use script::dom::element::{HTMLTableElementTypeId, HTMLTableHeaderCellElementTypeId};
+use script::dom::element::{HTMLTableRowElementTypeId, HTMLTableSectionElementTypeId};
 use script::dom::node::{CommentNodeTypeId, DoctypeNodeTypeId, DocumentFragmentNodeTypeId};
 use script::dom::node::{DocumentNodeTypeId, ElementNodeTypeId, ProcessingInstructionNodeTypeId};
 use script::dom::node::{TextNodeTypeId};
 use script::dom::text::Text;
-use style::computed_values::{display, position, float, white_space};
-use style::ComputedValues;
+use servo_util::geometry::Au;
 use servo_util::namespace;
-use servo_util::url::parse_url;
-use servo_util::url::is_image_data;
+use servo_util::smallvec::SmallVec;
 use servo_util::str::is_whitespace;
-
-use extra::url::Url;
-use sync::Arc;
+use servo_util::url::{is_image_data, parse_url};
 use std::mem;
 use std::num::Zero;
+use style::ComputedValues;
+use style::computed_values::{display, position, float, white_space};
+use sync::Arc;
 
 /// The results of flow construction for a DOM node.
 pub enum ConstructionResult {
@@ -75,7 +78,7 @@ pub enum ConstructionResult {
     /// This node contributed a flow at the proper position in the tree.
     /// Nothing more needs to be done for this node. It has bubbled up fixed
     /// and absolute descendant flows that have a CB above it.
-    FlowConstructionResult(~Flow, AbsDescendants, FixedDescendants),
+    FlowConstructionResult(~Flow, AbsDescendants),
 
     /// This node contributed some object or objects that will be needed to construct a proper flow
     /// later up the tree, but these objects have not yet found their home.
@@ -86,7 +89,7 @@ impl ConstructionResult {
     fn destroy(&mut self) {
         match *self {
             NoConstructionResult => {}
-            FlowConstructionResult(ref mut flow, _, _) => flow.destroy(),
+            FlowConstructionResult(ref mut flow, _) => flow.destroy(),
             ConstructionItemConstructionResult(ref mut item) => item.destroy(),
         }
     }
@@ -132,9 +135,6 @@ struct InlineBoxesConstructionResult {
 
     /// Any absolute descendants that we're bubbling up.
     abs_descendants: AbsDescendants,
-
-    /// Any fixed descendants that we're bubbling up.
-    fixed_descendants: FixedDescendants,
 }
 
 /// Represents an {ib} split that has not yet found the containing block that it belongs to. This
@@ -281,7 +281,8 @@ impl<'a> FlowConstructor<'a> {
     }
 
     /// Builds the `ImageBoxInfo` for the given image. This is out of line to guide inlining.
-    fn build_box_info_for_image(&mut self, node: &ThreadSafeLayoutNode, url: Option<Url>) -> SpecificBoxInfo {
+    fn build_box_info_for_image(&mut self, node: &ThreadSafeLayoutNode, url: Option<Url>)
+                                -> SpecificBoxInfo {
         match url {
             None => GenericBox,
             Some(url) => {
@@ -296,19 +297,25 @@ impl<'a> FlowConstructor<'a> {
     pub fn build_specific_box_info_for_node(&mut self, node: &ThreadSafeLayoutNode)
                                             -> SpecificBoxInfo {
         match node.type_id() {
-            ElementNodeTypeId(HTMLImageElementTypeId) => self.build_box_info_for_image(node, node.image_url()),
-            ElementNodeTypeId(HTMLIFrameElementTypeId) => IframeBox(IframeBoxInfo::new(node)),
-            ElementNodeTypeId(HTMLObjectElementTypeId) => {
+            Some(ElementNodeTypeId(HTMLImageElementTypeId)) => {
+                self.build_box_info_for_image(node, node.image_url())
+            }
+            Some(ElementNodeTypeId(HTMLIFrameElementTypeId)) => {
+                IframeBox(IframeBoxInfo::new(node))
+            }
+            Some(ElementNodeTypeId(HTMLObjectElementTypeId)) => {
                 let data = node.get_object_data(&self.layout_context.url);
                 self.build_box_info_for_image(node, data)
             }
-            ElementNodeTypeId(HTMLTableElementTypeId) => TableWrapperBox,
-            ElementNodeTypeId(HTMLTableColElementTypeId) => TableColumnBox(TableColumnBoxInfo::new(node)),
-            ElementNodeTypeId(HTMLTableDataCellElementTypeId) |
-            ElementNodeTypeId(HTMLTableHeaderCellElementTypeId) => TableCellBox,
-            ElementNodeTypeId(HTMLTableRowElementTypeId) |
-            ElementNodeTypeId(HTMLTableSectionElementTypeId) => TableRowBox,
-            TextNodeTypeId => UnscannedTextBox(UnscannedTextBoxInfo::new(node)),
+            Some(ElementNodeTypeId(HTMLTableElementTypeId)) => TableWrapperBox,
+            Some(ElementNodeTypeId(HTMLTableColElementTypeId)) => {
+                TableColumnBox(TableColumnBoxInfo::new(node))
+            }
+            Some(ElementNodeTypeId(HTMLTableDataCellElementTypeId)) |
+            Some(ElementNodeTypeId(HTMLTableHeaderCellElementTypeId)) => TableCellBox,
+            Some(ElementNodeTypeId(HTMLTableRowElementTypeId)) |
+            Some(ElementNodeTypeId(HTMLTableSectionElementTypeId)) => TableRowBox,
+            None | Some(TextNodeTypeId) => UnscannedTextBox(UnscannedTextBoxInfo::new(node)),
             _ => GenericBox,
         }
     }
@@ -352,6 +359,115 @@ impl<'a> FlowConstructor<'a> {
         }
     }
 
+    fn build_block_flow_using_children_construction_result(&mut self,
+                                                           flow: &mut ~Flow,
+                                                           consecutive_siblings: &mut ~[~Flow],
+                                                           node: &ThreadSafeLayoutNode,
+                                                           kid: ThreadSafeLayoutNode,
+                                                           opt_boxes_for_inline_flow: &mut Option<~[Box]>,
+                                                           abs_descendants: &mut Descendants,
+                                                           first_box: &mut bool) {
+        match kid.swap_out_construction_result() {
+            NoConstructionResult => {}
+            FlowConstructionResult(kid_flow, kid_abs_descendants) => {
+                // If kid_flow is TableCaptionFlow, kid_flow should be added under
+                // TableWrapperFlow.
+                if flow.is_table() && kid_flow.is_table_caption() {
+                    kid.set_flow_construction_result(FlowConstructionResult(
+                            kid_flow,
+                            Descendants::new()))
+                } else if flow.need_anonymous_flow(kid_flow) {
+                    consecutive_siblings.push(kid_flow)
+                } else {
+                    // Strip ignorable whitespace from the start of this flow per CSS 2.1 §
+                    // 9.2.1.1.
+                    if flow.is_table_kind() || *first_box {
+                        strip_ignorable_whitespace_from_start(opt_boxes_for_inline_flow);
+                        *first_box = false
+                    }
+
+                    // Flush any inline boxes that we were gathering up. This allows us to handle
+                    // {ib} splits.
+                    debug!("flushing {} inline box(es) to flow A",
+                            opt_boxes_for_inline_flow.as_ref()
+                            .map_or(0, |boxes| boxes.len()));
+                    self.flush_inline_boxes_to_flow_or_list_if_necessary(
+                        opt_boxes_for_inline_flow,
+                        flow,
+                        consecutive_siblings,
+                        node);
+                    if !consecutive_siblings.is_empty() {
+                        let consecutive_siblings = mem::replace(consecutive_siblings, ~[]);
+                        self.generate_anonymous_missing_child(consecutive_siblings,
+                                                              flow,
+                                                              node);
+                    }
+                    flow.add_new_child(kid_flow);
+                }
+                abs_descendants.push_descendants(kid_abs_descendants);
+            }
+            ConstructionItemConstructionResult(InlineBoxesConstructionItem(
+                    InlineBoxesConstructionResult {
+                        splits: opt_splits,
+                        boxes: boxes,
+                        abs_descendants: kid_abs_descendants,
+                    })) => {
+                // Add any {ib} splits.
+                match opt_splits {
+                    None => {}
+                    Some(splits) => {
+                        for split in splits.move_iter() {
+                            // Pull apart the {ib} split object and push its predecessor boxes
+                            // onto the list.
+                            let InlineBlockSplit {
+                                predecessor_boxes: predecessor_boxes,
+                                flow: kid_flow
+                            } = split;
+                            opt_boxes_for_inline_flow.push_all_move(predecessor_boxes);
+
+                            // If this is the first box in flow, then strip ignorable
+                            // whitespace per CSS 2.1 § 9.2.1.1.
+                            if *first_box {
+                                strip_ignorable_whitespace_from_start(
+                                    opt_boxes_for_inline_flow);
+                                *first_box = false
+                            }
+
+                            // Flush any inline boxes that we were gathering up.
+                            debug!("flushing {} inline box(es) to flow A",
+                                   opt_boxes_for_inline_flow.as_ref()
+                                                            .map_or(0, |boxes| boxes.len()));
+                            self.flush_inline_boxes_to_flow_or_list_if_necessary(
+                                    opt_boxes_for_inline_flow,
+                                    flow,
+                                    consecutive_siblings,
+                                    node);
+
+                            // Push the flow generated by the {ib} split onto our list of
+                            // flows.
+                            if flow.need_anonymous_flow(kid_flow) {
+                                consecutive_siblings.push(kid_flow)
+                            } else {
+                                flow.add_new_child(kid_flow)
+                            }
+                        }
+                    }
+                }
+
+                // Add the boxes to the list we're maintaining.
+                opt_boxes_for_inline_flow.push_all_move(boxes);
+                abs_descendants.push_descendants(kid_abs_descendants);
+            }
+            ConstructionItemConstructionResult(WhitespaceConstructionItem(..)) => {
+                // Nothing to do here.
+            }
+            ConstructionItemConstructionResult(TableColumnBoxConstructionItem(_)) => {
+                // TODO: Implement anonymous table objects for missing parents
+                // CSS 2.1 § 17.2.1, step 3-2
+            }
+        }
+    }
+
     /// Build block flow for current node using information from children nodes.
     ///
     /// Consume results from children and combine them, handling {ib} splits.
@@ -367,109 +483,22 @@ impl<'a> FlowConstructor<'a> {
         let mut opt_boxes_for_inline_flow = None;
         let mut consecutive_siblings = ~[];
         let mut first_box = true;
+
         // List of absolute descendants, in tree order.
         let mut abs_descendants = Descendants::new();
-        let mut fixed_descendants = Descendants::new();
         for kid in node.children() {
-            match kid.swap_out_construction_result() {
-                NoConstructionResult => {}
-                FlowConstructionResult(kid_flow, kid_abs_descendants, kid_fixed_descendants) => {
-                    // If kid_flow is TableCaptionFlow, kid_flow should be added under TableWrapperFlow.
-                    if flow.is_table() && kid_flow.is_table_caption() {
-                        kid.set_flow_construction_result(FlowConstructionResult(kid_flow,
-                                                                                Descendants::new(),
-                                                                                Descendants::new()))
-                    } else if flow.need_anonymous_flow(kid_flow) {
-                        consecutive_siblings.push(kid_flow)
-                    } else {
-                        // Strip ignorable whitespace from the start of this flow per CSS 2.1 §
-                        // 9.2.1.1.
-                        if flow.is_table_kind() || first_box {
-                            strip_ignorable_whitespace_from_start(&mut opt_boxes_for_inline_flow);
-                            first_box = false
-                        }
-
-                        // Flush any inline boxes that we were gathering up. This allows us to handle
-                        // {ib} splits.
-                        debug!("flushing {} inline box(es) to flow A",
-                                opt_boxes_for_inline_flow.as_ref()
-                                .map_or(0, |boxes| boxes.len()));
-                        self.flush_inline_boxes_to_flow_or_list_if_necessary(&mut opt_boxes_for_inline_flow,
-                                                                             &mut flow,
-                                                                             &mut consecutive_siblings,
-                                                                             node);
-                        if !consecutive_siblings.is_empty() {
-                            self.generate_anonymous_missing_child(consecutive_siblings, &mut flow, node);
-                            consecutive_siblings = ~[];
-                        }
-                        flow.add_new_child(kid_flow);
-                    }
-                    abs_descendants.push_descendants(kid_abs_descendants);
-                    fixed_descendants.push_descendants(kid_fixed_descendants);
-                }
-                ConstructionItemConstructionResult(InlineBoxesConstructionItem(
-                        InlineBoxesConstructionResult {
-                            splits: opt_splits,
-                            boxes: boxes,
-                            abs_descendants: kid_abs_descendants,
-                            fixed_descendants: kid_fixed_descendants,
-                        })) => {
-                    // Add any {ib} splits.
-                    match opt_splits {
-                        None => {}
-                        Some(splits) => {
-                            for split in splits.move_iter() {
-                                // Pull apart the {ib} split object and push its predecessor boxes
-                                // onto the list.
-                                let InlineBlockSplit {
-                                    predecessor_boxes: predecessor_boxes,
-                                    flow: kid_flow
-                                } = split;
-                                opt_boxes_for_inline_flow.push_all_move(predecessor_boxes);
-
-                                // If this is the first box in flow, then strip ignorable
-                                // whitespace per CSS 2.1 § 9.2.1.1.
-                                if first_box {
-                                    strip_ignorable_whitespace_from_start(
-                                        &mut opt_boxes_for_inline_flow);
-                                    first_box = false
-                                }
-
-                                // Flush any inline boxes that we were gathering up.
-                                debug!("flushing {} inline box(es) to flow A",
-                                       opt_boxes_for_inline_flow.as_ref()
-                                                                .map_or(0,
-                                                                        |boxes| boxes.len()));
-                                self.flush_inline_boxes_to_flow_or_list_if_necessary(
-                                        &mut opt_boxes_for_inline_flow,
-                                        &mut flow,
-                                        &mut consecutive_siblings,
-                                        node);
-
-                                // Push the flow generated by the {ib} split onto our list of
-                                // flows.
-                                if flow.need_anonymous_flow(kid_flow) {
-                                    consecutive_siblings.push(kid_flow)
-                                } else {
-                                    flow.add_new_child(kid_flow)
-                                }
-                            }
-                        }
-                    }
-
-                    // Add the boxes to the list we're maintaining.
-                    opt_boxes_for_inline_flow.push_all_move(boxes);
-                    abs_descendants.push_descendants(kid_abs_descendants);
-                    fixed_descendants.push_descendants(kid_fixed_descendants);
-                }
-                ConstructionItemConstructionResult(WhitespaceConstructionItem(..)) => {
-                    // Nothing to do here.
-                }
-                ConstructionItemConstructionResult(TableColumnBoxConstructionItem(_)) => {
-                    // TODO: Implement anonymous table objects for missing parents
-                    // CSS 2.1 § 17.2.1, step 3-2
-                }
+            if kid.get_element_type() != Normal {
+                self.process(&kid);
             }
+
+            self.build_block_flow_using_children_construction_result(
+                &mut flow,
+                &mut consecutive_siblings,
+                node,
+                kid,
+                &mut opt_boxes_for_inline_flow,
+                &mut abs_descendants,
+                &mut first_box);
         }
 
         // Perform a final flush of any inline boxes that we were gathering up to handle {ib}
@@ -493,16 +522,13 @@ impl<'a> FlowConstructor<'a> {
             flow.set_abs_descendants(abs_descendants);
             abs_descendants = Descendants::new();
 
-            if is_fixed_positioned {
-                // Send itself along with the other fixed descendants.
-                fixed_descendants.push(Rawlink::some(flow));
-            } else if is_absolutely_positioned {
+            if is_fixed_positioned || is_absolutely_positioned {
                 // This is now the only absolute flow in the subtree which hasn't yet
                 // reached its CB.
                 abs_descendants.push(Rawlink::some(flow));
             }
         }
-        FlowConstructionResult(flow, abs_descendants, fixed_descendants)
+        FlowConstructionResult(flow, abs_descendants)
     }
 
     /// Builds a flow for a node with `display: block`. This yields a `BlockFlow` with possibly
@@ -521,7 +547,6 @@ impl<'a> FlowConstructor<'a> {
         self.build_flow_using_children(flow, node)
     }
 
-
     /// Concatenates the boxes of kids, adding in our own borders/padding/margins if necessary.
     /// Returns the `InlineBoxesConstructionResult`, if any. There will be no
     /// `InlineBoxesConstructionResult` if this node consisted entirely of ignorable whitespace.
@@ -530,13 +555,12 @@ impl<'a> FlowConstructor<'a> {
         let mut opt_inline_block_splits = None;
         let mut opt_box_accumulator = None;
         let mut abs_descendants = Descendants::new();
-        let mut fixed_descendants = Descendants::new();
 
         // Concatenate all the boxes of our kids, creating {ib} splits as necessary.
         for kid in node.children() {
             match kid.swap_out_construction_result() {
                 NoConstructionResult => {}
-                FlowConstructionResult(flow, kid_abs_descendants, kid_fixed_descendants) => {
+                FlowConstructionResult(flow, kid_abs_descendants) => {
                     // {ib} split. Flush the accumulator to our new split and make a new
                     // accumulator to hold any subsequent boxes we come across.
                     let split = InlineBlockSplit {
@@ -545,14 +569,12 @@ impl<'a> FlowConstructor<'a> {
                     };
                     opt_inline_block_splits.push(split);
                     abs_descendants.push_descendants(kid_abs_descendants);
-                    fixed_descendants.push_descendants(kid_fixed_descendants);
                 }
                 ConstructionItemConstructionResult(InlineBoxesConstructionItem(
                         InlineBoxesConstructionResult {
                             splits: opt_splits,
                             boxes: boxes,
                             abs_descendants: kid_abs_descendants,
-                            fixed_descendants: kid_fixed_descendants,
                         })) => {
 
                     // Bubble up {ib} splits.
@@ -579,7 +601,6 @@ impl<'a> FlowConstructor<'a> {
                     // Push residual boxes.
                     opt_box_accumulator.push_all_move(boxes);
                     abs_descendants.push_descendants(kid_abs_descendants);
-                    fixed_descendants.push_descendants(kid_fixed_descendants);
                 }
                 ConstructionItemConstructionResult(WhitespaceConstructionItem(whitespace_node,
                                                                               whitespace_style))
@@ -612,7 +633,7 @@ impl<'a> FlowConstructor<'a> {
                         for box_ in boxes.iter() {
                             total.push(box_);
                         }
-                        self.set_inline_info_for_inline_child(&total, node);
+                        self.set_inline_info_for_inline_child(total, node);
 
                     },
                     None => {
@@ -622,7 +643,7 @@ impl<'a> FlowConstructor<'a> {
                                 total.push(box_);
                             }
                         }
-                        self.set_inline_info_for_inline_child(&total, node);
+                        self.set_inline_info_for_inline_child(total, node);
                     }
                 }
             },
@@ -633,7 +654,7 @@ impl<'a> FlowConstructor<'a> {
                         for box_ in boxes.iter() {
                             total.push(box_);
                         }
-                        self.set_inline_info_for_inline_child(&total, node);
+                        self.set_inline_info_for_inline_child(total, node);
                     },
                     None => {}
                 }
@@ -648,7 +669,6 @@ impl<'a> FlowConstructor<'a> {
                 splits: opt_inline_block_splits,
                 boxes: opt_box_accumulator.to_vec(),
                 abs_descendants: abs_descendants,
-                fixed_descendants: fixed_descendants,
             });
             ConstructionItemConstructionResult(construction_item)
         } else {
@@ -656,8 +676,9 @@ impl<'a> FlowConstructor<'a> {
         }
     }
 
+    // FIXME(#1999, pcwalton): Why does this function create a box only to throw it away???
     fn set_inline_info_for_inline_child(&mut self,
-                                        boxes: &~[&Box],
+                                        boxes: &[&Box],
                                         parent_node: &ThreadSafeLayoutNode) {
         let parent_box = Box::new(self, parent_node);
         let font_style = parent_box.font_style();
@@ -671,33 +692,39 @@ impl<'a> FlowConstructor<'a> {
         let boxes_len = boxes.len();
         parent_box.compute_borders(parent_box.style());
 
+        // FIXME(#2000, pcwalton): I suspect that `Au(0)` is not correct for the containing block
+        // width.
+        parent_box.compute_padding(parent_box.style(), Au(0));
+
         for (i, box_) in boxes.iter().enumerate() {
             if box_.inline_info.with( |data| data.is_none() ) {
                 box_.inline_info.set(Some(InlineInfo::new()));
             }
 
             let mut border = parent_box.border.get();
+            let mut padding = parent_box.padding.get();
             if i != 0 {
                 border.left = Zero::zero();
+                padding.left = Zero::zero()
             }
             if i != (boxes_len - 1) {
                 border.right = Zero::zero();
+                padding.right = Zero::zero()
             }
 
             let mut info = box_.inline_info.borrow_mut();
             match info.get() {
                 &Some(ref mut info) => {
-                    // TODO(ksh8281) compute margin,padding
-                    info.parent_info.push(
-                        InlineParentInfo {
-                            padding: Zero::zero(),
-                            border: border,
-                            margin: Zero::zero(),
-                            style: parent_box.style.clone(),
-                            font_ascent: font_ascent,
-                            font_descent: font_descent,
-                            node: OpaqueNode::from_thread_safe_layout_node(parent_node),
-                        });
+                    // TODO(ksh8281): Compute margins.
+                    info.parent_info.push(InlineParentInfo {
+                        padding: padding,
+                        border: border,
+                        margin: Zero::zero(),
+                        style: parent_box.style.clone(),
+                        font_ascent: font_ascent,
+                        font_descent: font_descent,
+                        node: OpaqueNodeMethods::from_thread_safe_layout_node(parent_node),
+                    })
                 },
                 &None => {}
             }
@@ -712,20 +739,22 @@ impl<'a> FlowConstructor<'a> {
         }
 
         // If this node is ignorable whitespace, bail out now.
+        //
+        // FIXME(#2001, pcwalton): Don't do this if there's padding or borders.
         if node.is_ignorable_whitespace() {
-            let opaque_node = OpaqueNode::from_thread_safe_layout_node(node);
+            let opaque_node = OpaqueNodeMethods::from_thread_safe_layout_node(node);
             return ConstructionItemConstructionResult(WhitespaceConstructionItem(
                 opaque_node,
                 node.style().clone()))
         }
 
+        let mut opt_box_accumulator = None;
+        opt_box_accumulator.push(Box::new(self, node));
+
         let construction_item = InlineBoxesConstructionItem(InlineBoxesConstructionResult {
             splits: None,
-            boxes: ~[
-                Box::new(self, node)
-            ],
+            boxes: opt_box_accumulator.to_vec(),
             abs_descendants: Descendants::new(),
-            fixed_descendants: Descendants::new(),
         });
         ConstructionItemConstructionResult(construction_item)
     }
@@ -750,7 +779,7 @@ impl<'a> FlowConstructor<'a> {
         for kid in node.children() {
             match kid.swap_out_construction_result() {
                 NoConstructionResult | ConstructionItemConstructionResult(_) => {}
-                FlowConstructionResult(kid_flow, _, _) => {
+                FlowConstructionResult(kid_flow, _) => {
                     // Only kid flows with table-caption are matched here.
                     assert!(kid_flow.is_table_caption());
                     table_wrapper_flow.add_new_child(kid_flow);
@@ -761,8 +790,10 @@ impl<'a> FlowConstructor<'a> {
 
     /// Generates an anonymous table flow according to CSS 2.1 § 17.2.1, step 2.
     /// If necessary, generate recursively another anonymous table flow.
-    fn generate_anonymous_missing_child(&mut self, child_flows: ~[~Flow],
-                                        flow: &mut ~Flow, node: &ThreadSafeLayoutNode) {
+    fn generate_anonymous_missing_child(&mut self,
+                                        child_flows: ~[~Flow],
+                                        flow: &mut ~Flow,
+                                        node: &ThreadSafeLayoutNode) {
         let mut anonymous_flow = flow.generate_missing_child_flow(node);
         let mut consecutive_siblings = ~[];
         for kid_flow in child_flows.move_iter() {
@@ -805,10 +836,9 @@ impl<'a> FlowConstructor<'a> {
         // NOTE: The order of captions and table are not the same order as in the DOM tree.
         // All caption blocks are placed before the table flow
         match construction_result {
-            FlowConstructionResult(table_flow, table_abs_descendants, table_fixed_descendants) => {
+            FlowConstructionResult(table_flow, table_abs_descendants) => {
                 wrapper_flow.add_new_child(table_flow);
                 abs_descendants.push_descendants(table_abs_descendants);
-                fixed_descendants.push_descendants(table_fixed_descendants);
             }
             _ => {}
         }
@@ -832,7 +862,7 @@ impl<'a> FlowConstructor<'a> {
                 abs_descendants.push(Rawlink::some(wrapper_flow));
             }
         }
-        FlowConstructionResult(wrapper_flow, abs_descendants, fixed_descendants)
+        FlowConstructionResult(wrapper_flow, abs_descendants)
     }
 
     /// Builds a flow for a node with `display: table-caption`. This yields a `TableCaptionFlow`
@@ -904,7 +934,7 @@ impl<'a> FlowConstructor<'a> {
         let mut flow = ~TableColGroupFlow::from_node_and_boxes(node, box_, col_boxes) as ~Flow;
         flow.finish(self.layout_context);
 
-        FlowConstructionResult(flow, Descendants::new(), Descendants::new())
+        FlowConstructionResult(flow, Descendants::new())
     }
 }
 
@@ -922,16 +952,23 @@ impl<'a> PostorderNodeMutTraversal for FlowConstructor<'a> {
     fn process(&mut self, node: &ThreadSafeLayoutNode) -> bool {
         // Get the `display` property for this node, and determine whether this node is floated.
         let (display, float, positioning) = match node.type_id() {
-            ElementNodeTypeId(_) => {
+            None => {
+                // Pseudo-element.
+                let style = node.style().get();
+                (display::inline, style.Box.get().float, style.Box.get().position)
+            }
+            Some(ElementNodeTypeId(_)) => {
                 let style = node.style().get();
                 (style.Box.get().display, style.Box.get().float, style.Box.get().position)
             }
-            TextNodeTypeId => (display::inline, float::none, position::static_),
-            CommentNodeTypeId |
-            DoctypeNodeTypeId |
-            DocumentFragmentNodeTypeId |
-            DocumentNodeTypeId |
-            ProcessingInstructionNodeTypeId => (display::none, float::none, position::static_),
+            Some(TextNodeTypeId) => (display::inline, float::none, position::static_),
+            Some(CommentNodeTypeId) |
+            Some(DoctypeNodeTypeId) |
+            Some(DocumentFragmentNodeTypeId) |
+            Some(DocumentNodeTypeId) |
+            Some(ProcessingInstructionNodeTypeId) => {
+                (display::none, float::none, position::static_)
+            }
         };
 
         debug!("building flow for node: {:?} {:?}", display, float);
@@ -1044,21 +1081,22 @@ trait NodeUtils {
 impl<'ln> NodeUtils for ThreadSafeLayoutNode<'ln> {
     fn is_replaced_content(&self) -> bool {
         match self.type_id() {
-            TextNodeTypeId |
-            ProcessingInstructionNodeTypeId |
-            CommentNodeTypeId |
-            DoctypeNodeTypeId |
-            DocumentFragmentNodeTypeId |
-            DocumentNodeTypeId |
-            ElementNodeTypeId(HTMLImageElementTypeId) => true,
-            ElementNodeTypeId(HTMLObjectElementTypeId) => self.has_object_data(),
-            ElementNodeTypeId(_) => false,
+            Some(TextNodeTypeId) |
+            Some(ProcessingInstructionNodeTypeId) |
+            Some(CommentNodeTypeId) |
+            Some(DoctypeNodeTypeId) |
+            Some(DocumentFragmentNodeTypeId) |
+            Some(DocumentNodeTypeId) |
+            None |
+            Some(ElementNodeTypeId(HTMLImageElementTypeId)) => true,
+            Some(ElementNodeTypeId(HTMLObjectElementTypeId)) => self.has_object_data(),
+            Some(ElementNodeTypeId(_)) => false,
         }
     }
 
     fn is_ignorable_whitespace(&self) -> bool {
         match self.type_id() {
-            TextNodeTypeId => {
+            Some(TextNodeTypeId) => {
                 unsafe {
                     let text: JS<Text> = TextCast::to(self.get_jsmanaged()).unwrap();
                     if !is_whitespace(text.get().characterdata.data) {
@@ -1085,7 +1123,17 @@ impl<'ln> NodeUtils for ThreadSafeLayoutNode<'ln> {
     fn set_flow_construction_result(&self, result: ConstructionResult) {
         let mut layout_data_ref = self.mutate_layout_data();
         match *layout_data_ref.get() {
-            Some(ref mut layout_data) => layout_data.data.flow_construction_result = result,
+            Some(ref mut layout_data) =>{
+                match self.get_element_type() {
+                    Before | BeforeBlock => {
+                        layout_data.data.before_flow_construction_result = result
+                    },
+                    After | AfterBlock => {
+                        layout_data.data.after_flow_construction_result = result
+                    },
+                    Normal => layout_data.data.flow_construction_result = result,
+                }
+            },
             None => fail!("no layout data"),
         }
     }
@@ -1095,7 +1143,20 @@ impl<'ln> NodeUtils for ThreadSafeLayoutNode<'ln> {
         let mut layout_data_ref = self.mutate_layout_data();
         match *layout_data_ref.get() {
             Some(ref mut layout_data) => {
-                mem::replace(&mut layout_data.data.flow_construction_result, NoConstructionResult)
+                match self.get_element_type() {
+                    Before | BeforeBlock => {
+                        mem::replace(&mut layout_data.data.before_flow_construction_result,
+                                     NoConstructionResult)
+                    }
+                    After | AfterBlock => {
+                        mem::replace(&mut layout_data.data.after_flow_construction_result,
+                                     NoConstructionResult)
+                    }
+                    Normal => {
+                        mem::replace(&mut layout_data.data.flow_construction_result,
+                                     NoConstructionResult)
+                    }
+                }
             }
             None => fail!("no layout data"),
         }

src/components/main/layout/context.rs

@@ -5,10 +5,10 @@
 //! Data needed by the layout task.
 
 use css::matching::{ApplicableDeclarationsCache, StyleSharingCandidateCache};
-use layout::util::OpaqueNode;
 
 use extra::url::Url;
 use geom::size::Size2D;
+use gfx::display_list::OpaqueNode;
 use gfx::font_context::{FontContext, FontContextInfo};
 use green::task::GreenTask;
 use script::layout_interface::LayoutChan;

src/components/main/layout/display_list_builder.rs

@@ -4,39 +4,34 @@
 
 //! Constructs display lists from boxes.
 
-use layout::box_::Box;
 use layout::context::LayoutContext;
-use layout::util::OpaqueNode;
 
+use geom::{Point2D, Rect, Size2D};
+use gfx::render_task::RenderLayer;
 use gfx;
+use servo_util::geometry::Au;
+use servo_util::smallvec::SmallVec0;
 use style;
 
-pub trait ExtraDisplayListData {
-    fn new(box_: &Box) -> Self;
-}
-
-pub type Nothing = ();
-
-impl ExtraDisplayListData for OpaqueNode {
-    fn new(box_: &Box) -> OpaqueNode {
-        box_.node
-    }
-}
-
-impl ExtraDisplayListData for Nothing {
-    fn new(_: &Box) -> Nothing {
-        ()
-    }
-}
-
-/// A builder object that manages display list builder should mainly hold information about the
-/// initial request and desired result--for example, whether the `DisplayList` is to be used for
-/// painting or hit testing. This can affect which boxes are created.
-///
-/// Right now, the builder isn't used for much, but it establishes the pattern we'll need once we
-/// support display-list-based hit testing and so forth.
+/// Manages the information needed to construct the display list.
 pub struct DisplayListBuilder<'a> {
     ctx: &'a LayoutContext,
+
+    /// A list of render layers that we've built up, root layer not included.
+    layers: SmallVec0<RenderLayer>,
+
+    /// The dirty rect.
+    dirty: Rect<Au>,
+}
+
+/// Information needed at each step of the display list building traversal.
+pub struct DisplayListBuildingInfo {
+    /// The size of the containing block for relatively-positioned descendants.
+    relative_containing_block_size: Size2D<Au>,
+    /// The position and size of the absolute containing block.
+    absolute_containing_block_position: Point2D<Au>,
+    /// Whether the absolute containing block forces positioned descendants to be layerized.
+    layers_needed_for_positioned_flows: bool,
 }
 
 //

src/components/main/layout/flow.rs

@@ -26,14 +26,16 @@
 ///   similar methods.
 
 use css::node_style::StyledNode;
-use layout::block::{BlockFlow};
+use layout::block::BlockFlow;
 use layout::box_::{Box, TableRowBox, TableCellBox};
-use layout::context::LayoutContext;
 use layout::construct::OptVector;
-use layout::display_list_builder::{DisplayListBuilder, ExtraDisplayListData};
+use layout::context::LayoutContext;
+use layout::display_list_builder::{DisplayListBuilder, DisplayListBuildingInfo, ToGfxColor};
 use layout::floats::Floats;
+use layout::flow_list::{FlowList, Link, Rawlink, FlowListIterator, MutFlowListIterator};
 use layout::incremental::RestyleDamage;
 use layout::inline::InlineFlow;
+use layout::model::{CollapsibleMargins, IntrinsicWidths, MarginCollapseInfo};
 use layout::parallel::FlowParallelInfo;
 use layout::parallel;
 use layout::table_wrapper::TableWrapperFlow;
@@ -44,24 +46,22 @@ use layout::table_row::TableRowFlow;
 use layout::table_caption::TableCaptionFlow;
 use layout::table_cell::TableCellFlow;
 use layout::wrapper::ThreadSafeLayoutNode;
-use layout::flow_list::{FlowList, Link, Rawlink, FlowListIterator, MutFlowListIterator};
 
 use collections::Deque;
-use geom::point::Point2D;
 use geom::Size2D;
+use geom::point::Point2D;
 use geom::rect::Rect;
-use gfx::display_list::{ClipDisplayItemClass, DisplayListCollection, DisplayList};
-use layout::display_list_builder::ToGfxColor;
 use gfx::color::Color;
-use servo_util::smallvec::{SmallVec, SmallVec0};
+use gfx::display_list::StackingContext;
+use servo_msg::compositor_msg::LayerId;
 use servo_util::geometry::Au;
+use servo_util::smallvec::{SmallVec, SmallVec0};
 use std::cast;
-use std::cell::RefCell;
+use std::iter::Zip;
 use std::sync::atomics::Relaxed;
 use std::vec::MutItems;
-use std::iter::Zip;
 use style::ComputedValues;
-use style::computed_values::{text_align, position};
+use style::computed_values::{clear, position, text_align};
 
 /// Virtual methods that make up a float context.
 ///
@@ -126,6 +126,24 @@ pub trait Flow {
         fail!("called as_table_cell() on a non-tablecell flow")
     }
 
+    /// If this is a table row or table rowgroup or table flow, returns column widths.
+    /// Fails otherwise.
+    fn col_widths<'a>(&'a mut self) -> &'a mut ~[Au] {
+        fail!("called col_widths() on an other flow than table-row/table-rowgroup/table")
+    }
+
+    /// If this is a table row flow or table rowgroup flow or table flow, returns column min widths.
+    /// Fails otherwise.
+    fn col_min_widths<'a>(&'a self) -> &'a ~[Au] {
+        fail!("called col_min_widths() on an other flow than table-row/table-rowgroup/table")
+    }
+
+    /// If this is a table row flow or table rowgroup flow or table flow, returns column min widths.
+    /// Fails otherwise.
+    fn col_pref_widths<'a>(&'a self) -> &'a ~[Au] {
+        fail!("called col_pref_widths() on an other flow than table-row/table-rowgroup/table")
+    }
+
     // Main methods
 
     /// Pass 1 of reflow: computes minimum and preferred widths.
@@ -148,15 +166,10 @@ pub trait Flow {
         fail!("assign_height_inorder not yet implemented")
     }
 
-    /// Collapses margins with the parent flow. This runs as part of assign-heights.
-    fn collapse_margins(&mut self,
-                        _top_margin_collapsible: bool,
-                        _first_in_flow: &mut bool,
-                        _margin_top: &mut Au,
-                        _top_offset: &mut Au,
-                        _collapsing: &mut Au,
-                        _collapsible: &mut Au) {
-        fail!("collapse_margins not yet implemented")
+    fn compute_collapsible_top_margin(&mut self,
+                                      _layout_context: &mut LayoutContext,
+                                      _margin_collapse_info: &mut MarginCollapseInfo) {
+        // The default implementation is a no-op.
     }
 
     /// Marks this flow as the root flow. The default implementation is a no-op.
@@ -209,6 +222,11 @@ pub trait Flow {
         false
     }
 
+    /// Returns true if this is an absolute containing block.
+    fn is_absolute_containing_block(&self) -> bool {
+        false
+    }
+
     /// Return the dimensions of the CB generated _by_ this flow for absolute descendants.
     fn generated_cb_size(&self) -> Size2D<Au> {
         fail!("generated_cb_size not yet implemented")
@@ -219,6 +237,14 @@ pub trait Flow {
         fail!("this is not the CB-generating flow you're looking for")
     }
 
+    /// Returns a layer ID for the given fragment.
+    fn layer_id(&self, fragment_id: uint) -> LayerId {
+        unsafe {
+            let pointer: uint = cast::transmute(self);
+            LayerId(pointer, fragment_id)
+        }
+    }
+
     /// Returns a debugging string describing this flow.
     fn debug_str(&self) -> ~str {
         ~"???"
@@ -336,16 +362,11 @@ pub trait MutableFlowUtils {
     /// Computes the overflow region for this flow.
     fn store_overflow(self, _: &mut LayoutContext);
 
-    /// builds the display lists
-    fn build_display_lists<E:ExtraDisplayListData>(
-                          self,
-                          builder: &DisplayListBuilder,
-                          container_block_size: &Size2D<Au>,
-                          absolute_cb_abs_position: Point2D<Au>,
-                          dirty: &Rect<Au>,
-                          index: uint,
-                          mut list: &RefCell<DisplayListCollection<E>>)
-                          -> bool;
+    /// Builds the display lists for this flow and its descendants.
+    fn build_display_list(self,
+                          stacking_context: &mut StackingContext,
+                          builder: &mut DisplayListBuilder,
+                          info: &DisplayListBuildingInfo);
 
     /// Destroys the flow.
     fn destroy(self);
@@ -369,11 +390,6 @@ pub trait MutableOwnedFlowUtils {
     /// Set this flow as the Containing Block for all the absolute descendants.
     fn set_abs_descendants(&mut self, abs_descendants: AbsDescendants);
 
-    /// Set fixed descendants for this flow.
-    ///
-    /// Set yourself as the Containing Block for all the fixed descendants.
-    fn set_fixed_descendants(&mut self, fixed_descendants: AbsDescendants);
-
     /// Destroys the flow.
     fn destroy(&mut self);
 }
@@ -606,6 +622,17 @@ bitfield!(FlowFlags, override_overline, set_override_overline, 0b0000_0100)
 // NB: If you update this, you need to update TEXT_DECORATION_OVERRIDE_BITMASK.
 bitfield!(FlowFlags, override_line_through, set_override_line_through, 0b0000_1000)
 
+// Whether this flow contains a flow that has its own layer within the same absolute containing
+// block.
+bitfield!(FlowFlags,
+          layers_needed_for_descendants,
+          set_layers_needed_for_descendants,
+          0b0100_0000)
+
+// Whether this flow must have its own layer. Even if this flag is not set, it might get its own
+// layer if it's deemed to be likely to overlap flows with their own layer.
+bitfield!(FlowFlags, needs_layer, set_needs_layer, 0b1000_0000)
+
 // The text alignment for this flow.
 impl FlowFlags {
     #[inline]
@@ -690,7 +717,6 @@ impl Descendants {
 }
 
 pub type AbsDescendants = Descendants;
-pub type FixedDescendants = Descendants;
 
 type DescendantIter<'a> = MutItems<'a, Rawlink>;
 
@@ -708,12 +734,16 @@ pub struct BaseFlow {
     /* layout computations */
     // TODO: min/pref and position are used during disjoint phases of
     // layout; maybe combine into a single enum to save space.
-    min_width: Au,
-    pref_width: Au,
+    intrinsic_widths: IntrinsicWidths,
 
-    /// The upper left corner of the box representing this flow, relative to
-    /// the box representing its parent flow.
-    /// For absolute flows, this represents the position wrt to its Containing Block.
+    /// The upper left corner of the box representing this flow, relative to the box representing
+    /// its parent flow.
+    ///
+    /// For absolute flows, this represents the position with respect to its *containing block*.
+    ///
+    /// This does not include margins in the block flow direction, because those can collapse. So
+    /// for the block direction (usually vertical), this represents the *border box*. For the
+    /// inline direction (usually horizontal), this represents the *margin box*.
     position: Rect<Au>,
 
     /// The amount of overflow of this flow, relative to the containing block. Must include all the
@@ -728,6 +758,9 @@ pub struct BaseFlow {
     /// The floats next to this flow.
     floats: Floats,
 
+    /// The value of this flow's `clear` property, if any.
+    clear: clear::T,
+
     /// For normal flows, this is the number of floated descendants that are
     /// not contained within any other floated descendant of this flow. For
     /// floats, it is 1.
@@ -735,15 +768,15 @@ pub struct BaseFlow {
     /// decide whether to do an in-order traversal for assign_height.
     num_floats: uint,
 
+    /// The collapsible margins for this flow, if any.
+    collapsible_margins: CollapsibleMargins,
+
     /// The position of this flow in page coordinates, computed during display list construction.
     abs_position: Point2D<Au>,
 
-    /// Details about descendants with position 'absolute' for which we are
-    /// the CB. This is in tree order. This includes any direct children.
+    /// Details about descendants with position 'absolute' or 'fixed' for which we are the
+    /// containing block. This is in tree order. This includes any direct children.
     abs_descendants: AbsDescendants,
-    /// Details about descendants with position 'fixed'.
-    /// TODO: Optimize this, because this will be set only for the root.
-    fixed_descendants: FixedDescendants,
 
     /// Offset wrt the nearest positioned ancestor - aka the Containing Block
     /// for any absolutely positioned elements.
@@ -800,8 +833,7 @@ impl BaseFlow {
             next_sibling: None,
             prev_sibling: Rawlink::none(),
 
-            min_width: Au::new(0),
-            pref_width: Au::new(0),
+            intrinsic_widths: IntrinsicWidths::new(),
             position: Au::zero_rect(),
             overflow: Au::zero_rect(),
 
@@ -809,9 +841,10 @@ impl BaseFlow {
 
             floats: Floats::new(),
             num_floats: 0,
+            collapsible_margins: CollapsibleMargins::new(),
+            clear: clear::none,
             abs_position: Point2D(Au::new(0), Au::new(0)),
             abs_descendants: Descendants::new(),
-            fixed_descendants: Descendants::new(),
             absolute_static_x_offset: Au::new(0),
             fixed_static_x_offset: Au::new(0),
             absolute_cb: Rawlink::none(),
@@ -1068,6 +1101,7 @@ impl<'a> MutableFlowUtils for &'a mut Flow {
                 overflow = overflow.union(&kid_overflow)
             }
 
+            // FIXME(#2004, pcwalton): This is wrong for `position: fixed`.
             for descendant_link in mut_base(self).abs_descendants.iter() {
                 match descendant_link.resolve() {
                     Some(flow) => {
@@ -1078,183 +1112,62 @@ impl<'a> MutableFlowUtils for &'a mut Flow {
                     None => fail!("empty Rawlink to a descendant")
                 }
             }
-
-            if self.is_root() {
-                for fixed_descendant_link in mut_base(self).fixed_descendants.iter() {
-                    match fixed_descendant_link.resolve() {
-                        Some(flow) => {
-                            let mut kid_overflow = base(flow).overflow;
-                            kid_overflow = kid_overflow.translate(&my_position.origin);
-                            overflow = overflow.union(&kid_overflow)
-                        }
-                        None => fail!("empty Rawlink to a descendant")
-                    }
-                }
-            }
         }
         mut_base(self).overflow = overflow;
     }
 
-    /// Push display items for current flow and its children onto `list`.
+    /// Push display items for current flow and its descendants onto the appropriate display lists
+    /// of the given stacking context.
     ///
-    /// For InlineFlow, add display items for all its boxes onto list`.
-    /// For BlockFlow, add a ClipDisplayItemClass for itself and its children,
-    /// plus any other display items like border.
+    /// Arguments:
     ///
-    /// `container_block_size`: Size of the Containing Block for the current
-    /// flow. This is used for relative positioning (which resolves percentage
-    /// values for 'top', etc. after all Containing Block heights have been computed.)
-    /// `absolute_cb_abs_position`: Absolute position of the Containing Block
-    /// for the flow if it is absolutely positioned.
-    fn build_display_lists<E:ExtraDisplayListData>(
-                          self,
-                          builder: &DisplayListBuilder,
-                          container_block_size: &Size2D<Au>,
-                          absolute_cb_abs_position: Point2D<Au>,
-                          dirty: &Rect<Au>,
-                          mut index: uint,
-                          lists: &RefCell<DisplayListCollection<E>>)
-                          -> bool {
+    /// * `stacking_context`: The parent stacking context that this flow belongs to and to which
+    ///   display items will be added.
+    ///
+    /// * `builder`: The display list builder, which contains information used during the entire
+    ///   display list building pass.
+    ///
+    /// * `info`: Per-flow display list building information.
+    fn build_display_list(self,
+                          stacking_context: &mut StackingContext,
+                          builder: &mut DisplayListBuilder,
+                          info: &DisplayListBuildingInfo) {
         debug!("Flow: building display list");
-        index = match self.class() {
-            BlockFlowClass => self.as_block().build_display_list_block(builder,
-                                                                       container_block_size,
-                                                                       absolute_cb_abs_position,
-                                                                       dirty,
-                                                                       index,
-                                                                       lists),
-            InlineFlowClass => self.as_inline().build_display_list_inline(builder, container_block_size, dirty, index, lists),
-            TableWrapperFlowClass => self.as_table_wrapper().build_display_list_table_wrapper(builder,
-                                                                                              container_block_size,
-                                                                                              absolute_cb_abs_position,
-                                                                                              dirty,
-                                                                                              index,
-                                                                                              lists),
-            TableFlowClass => self.as_table().build_display_list_table(builder,
-                                                                       container_block_size,
-                                                                       absolute_cb_abs_position,
-                                                                       dirty,
-                                                                       index,
-                                                                       lists),
-            TableRowGroupFlowClass => self.as_table_rowgroup().build_display_list_table_rowgroup(builder,
-                                                                                                 container_block_size,
-                                                                                                 absolute_cb_abs_position,
-                                                                                                 dirty,
-                                                                                                 index,
-                                                                                                 lists),
-            TableRowFlowClass => self.as_table_row().build_display_list_table_row(builder,
-                                                                                  container_block_size,
-                                                                                  absolute_cb_abs_position,
-                                                                                  dirty,
-                                                                                  index,
-                                                                                  lists),
-            TableCaptionFlowClass => self.as_table_caption().build_display_list_table_caption(builder,
-                                                                                              container_block_size,
-                                                                                              absolute_cb_abs_position,
-                                                                                              dirty,
-                                                                                              index,
-                                                                                              lists),
-            TableCellFlowClass => self.as_table_cell().build_display_list_table_cell(builder,
-                                                                                     container_block_size,
-                                                                                     absolute_cb_abs_position,
-                                                                                     dirty,
-                                                                                     index,
-                                                                                     lists),
-            TableColGroupFlowClass => index,
-        };
-
-        if lists.with_mut(|lists| lists.lists[index].list.len() == 0) {
-            return true;
+        match self.class() {
+            BlockFlowClass => {
+                self.as_block().build_display_list_block(stacking_context, builder, info)
+            }
+            InlineFlowClass => {
+                self.as_inline().build_display_list_inline(stacking_context, builder, info)
+            }
+            TableWrapperFlowClass => {
+                self.as_table_wrapper().build_display_list_table_wrapper(stacking_context,
+                                                                         builder,
+                                                                         info)
+            }
+            TableFlowClass => {
+                self.as_table().build_display_list_table(stacking_context, builder, info)
+            }
+            TableRowGroupFlowClass => {
+                self.as_table_rowgroup().build_display_list_table_rowgroup(stacking_context,
+                                                                           builder,
+                                                                           info)
+            }
+            TableRowFlowClass => {
+                self.as_table_row().build_display_list_table_row(stacking_context, builder, info)
+            }
+            TableCaptionFlowClass => {
+                self.as_table_caption().build_display_list_table_caption(stacking_context,
+                                                                         builder,
+                                                                         info)
+            }
+            TableCellFlowClass => {
+                self.as_table_cell().build_display_list_table_cell(stacking_context, builder, info)
+            }
+            TableColGroupFlowClass => {
+                // Nothing to do here, as column groups don't render.
+            }
         }
-
-        if self.is_block_container() || self.is_table_kind() {
-            let block = self.as_block();
-            let mut child_lists = DisplayListCollection::new();
-            child_lists.add_list(DisplayList::new());
-            let child_lists = RefCell::new(child_lists);
-            let container_block_size;
-            let abs_cb_position;
-            // TODO(pradeep): Move this into a generated CB function and stuff in Flow.
-            match block.box_ {
-                Some(ref box_) => {
-                    // The Containing Block formed by a Block for relatively
-                    // positioned descendants is the content box.
-                    container_block_size = box_.content_box_size();
-
-                    abs_cb_position = if block.is_positioned() {
-                        block.base.abs_position + block.generated_cb_position()
-                    } else {
-                        absolute_cb_abs_position
-                    };
-                }
-                None => fail!("Flow: block container should have a box_")
-            }
-
-            for kid in block.base.child_iter() {
-                if kid.is_absolutely_positioned() {
-                    // All absolute flows will be handled by their CB.
-                    continue;
-                }
-                kid.build_display_lists(builder, &container_block_size,
-                                        abs_cb_position,
-                                        dirty, 0u, &child_lists);
-            }
-
-            // TODO: Maybe we should handle position 'absolute' and 'fixed'
-            // descendants before normal descendants just in case there is a
-            // problem when display-list building is parallel and both the
-            // original parent and this flow access the same absolute flow.
-            // Note that this can only be done once we have paint order
-            // working cos currently the later boxes paint over the absolute
-            // and fixed boxes :|
-            for abs_descendant_link in block.base.abs_descendants.iter() {
-                match abs_descendant_link.resolve() {
-                    Some(flow) => {
-                        // TODO(pradeep): Send in your abs_position directly.
-                        flow.build_display_lists(builder, &container_block_size,
-                                                 abs_cb_position,
-                                                 dirty, 0u, &child_lists);
-                    }
-                    None => fail!("empty Rawlink to a descendant")
-                }
-            }
-
-            if block.is_root() {
-                for fixed_descendant_link in block.base.fixed_descendants.iter() {
-                    match fixed_descendant_link.resolve() {
-                        Some(flow) => {
-                            flow.build_display_lists(builder, &container_block_size,
-                                                     abs_cb_position,
-                                                     dirty, 0u, &child_lists);
-                        }
-                        None => fail!("empty Rawlink to a descendant")
-                    }
-                }
-            }
-
-            let mut child_lists = Some(child_lists.unwrap());
-            // Find parent ClipDisplayItemClass and push all child display items
-            // under it
-            lists.with_mut(|lists| {
-                let mut child_lists = child_lists.take_unwrap();
-                let result = lists.lists[index].list.mut_rev_iter().position(|item| {
-                    match *item {
-                        ClipDisplayItemClass(ref mut item) => {
-                            item.child_list.push_all_move(child_lists.lists.shift().unwrap().list);
-                            true
-                        },
-                        _ => false,
-                    }
-                });
-
-                if result.is_none() {
-                    fail!("fail to find parent item");
-                }
-
-                lists.lists.push_all_move(child_lists.lists);
-            });
-        }
-        true
     }
 
     /// Destroys the flow.
@@ -1314,29 +1227,6 @@ impl MutableOwnedFlowUtils for ~Flow {
         }
     }
 
-    /// Set fixed descendants for this flow.
-    ///
-    /// Set yourself as the Containing Block for all the fixed descendants.
-    ///
-    /// Assumption: This is called in a bottom-up traversal, so that nothing
-    /// else is accessing the descendant flows.
-    /// Assumption: This is the root flow.
-    fn set_fixed_descendants(&mut self, fixed_descendants: FixedDescendants) {
-        let self_link = Rawlink::some(*self);
-        let block = self.as_block();
-        block.base.fixed_descendants = fixed_descendants;
-
-        for descendant_link in block.base.fixed_descendants.iter() {
-            match descendant_link.resolve() {
-                Some(flow) => {
-                    let base = mut_base(flow);
-                    base.absolute_cb = self_link.clone();
-                }
-                None => fail!("empty Rawlink to a descendant")
-            }
-        }
-    }
-
     /// Destroys the flow.
     fn destroy(&mut self) {
         let self_borrowed: &mut Flow = *self;

src/components/main/layout/inline.rs

@@ -3,23 +3,24 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use css::node_style::StyledNode;
-use layout::box_::{Box, CannotSplit, GenericBox, IframeBox, ImageBox, ScannedTextBox, SplitDidFit};
-use layout::box_::{SplitDidNotFit, UnscannedTextBox, InlineInfo};
-use layout::box_::{TableColumnBox, TableRowBox, TableWrapperBox, TableCellBox, TableBox};
+use layout::box_::{Box, CannotSplit, GenericBox, IframeBox, ImageBox, InlineInfo, ScannedTextBox};
+use layout::box_::{SplitDidFit, SplitDidNotFit, TableBox, TableCellBox, TableColumnBox};
+use layout::box_::{TableRowBox, TableWrapperBox, UnscannedTextBox};
 use layout::context::LayoutContext;
-use layout::display_list_builder::{DisplayListBuilder, ExtraDisplayListData};
+use layout::display_list_builder::{DisplayListBuilder, DisplayListBuildingInfo};
 use layout::floats::{FloatLeft, Floats, PlacementInfo};
 use layout::flow::{BaseFlow, FlowClass, Flow, InlineFlowClass};
 use layout::flow;
+use layout::model::IntrinsicWidths;
 use layout::util::ElementMapping;
 use layout::wrapper::ThreadSafeLayoutNode;
 
 use collections::{Deque, RingBuf};
 use geom::{Point2D, Rect, Size2D};
-use gfx::display_list::DisplayListCollection;
+use gfx::display_list::{ContentLevel, StackingContext};
 use servo_util::geometry::Au;
+use servo_util::geometry;
 use servo_util::range::Range;
-use std::cell::RefCell;
 use std::mem;
 use std::u16;
 use style::computed_values::{text_align, vertical_align, white_space};
@@ -480,17 +481,13 @@ impl InlineFlow {
         self.boxes = ~[];
     }
 
-    pub fn build_display_list_inline<E:ExtraDisplayListData>(
-                                     &self,
+    pub fn build_display_list_inline(&self,
+                                     stacking_context: &mut StackingContext,
                                      builder: &DisplayListBuilder,
-                                     container_block_size: &Size2D<Au>,
-                                     dirty: &Rect<Au>,
-                                     index: uint,
-                                     lists: &RefCell<DisplayListCollection<E>>)
-                                     -> uint {
+                                     info: &DisplayListBuildingInfo) {
         let abs_rect = Rect(self.base.abs_position, self.base.position.size);
-        if !abs_rect.intersects(dirty) {
-            return index;
+        if !abs_rect.intersects(&builder.dirty) {
+            return
         }
 
         // TODO(#228): Once we form line boxes and have their cached bounds, we can be smarter and
@@ -498,15 +495,19 @@ impl InlineFlow {
         debug!("Flow: building display list for {:u} inline boxes", self.boxes.len());
 
         for box_ in self.boxes.iter() {
-            let rel_offset: Point2D<Au> = box_.relative_position(container_block_size);
-            box_.build_display_list(builder, dirty, self.base.abs_position + rel_offset, (&*self) as &Flow, index, lists);
+            let rel_offset = box_.relative_position(&info.relative_containing_block_size);
+            box_.build_display_list(stacking_context,
+                                    builder,
+                                    info,
+                                    self.base.abs_position + rel_offset,
+                                    (&*self) as &Flow,
+                                    ContentLevel);
         }
 
         // TODO(#225): Should `inline-block` elements have flows as children of the inline flow or
         // should the flow be nested inside the box somehow?
 
-        // For now, don't traverse the subtree rooted here
-        index
+        // For now, don't traverse the subtree rooted here.
     }
 
     /// Returns the relative offset from the baseline for this box, taking into account the value
@@ -628,20 +629,19 @@ impl Flow for InlineFlow {
             child_base.floats = Floats::new();
         }
 
-        let mut min_width = Au::new(0);
-        let mut pref_width = Au::new(0);
-
+        let mut intrinsic_widths = IntrinsicWidths::new();
         for box_ in self.boxes.iter() {
             debug!("Flow: measuring {:s}", box_.debug_str());
             box_.compute_borders(box_.style());
-            let (this_minimum_width, this_preferred_width) =
-                box_.minimum_and_preferred_widths();
-            min_width = Au::max(min_width, this_minimum_width);
-            pref_width = Au::max(pref_width, this_preferred_width);
+
+            let box_intrinsic_widths = box_.intrinsic_widths();
+            intrinsic_widths.minimum_width = geometry::max(intrinsic_widths.minimum_width,
+                                                           box_intrinsic_widths.minimum_width);
+            intrinsic_widths.preferred_width = geometry::max(intrinsic_widths.preferred_width,
+                                                             box_intrinsic_widths.preferred_width);
         }
 
-        self.base.min_width = min_width;
-        self.base.pref_width = pref_width;
+        self.base.intrinsic_widths = intrinsic_widths;
         self.base.num_floats = num_floats;
     }
 
@@ -696,6 +696,7 @@ impl Flow for InlineFlow {
         //
         // TODO(pcwalton): Cache the linebox scanner?
         debug!("assign_height_inline: floats in: {:?}", self.base.floats);
+
         // assign height for inline boxes
         for box_ in self.boxes.iter() {
             box_.assign_replaced_height_if_necessary();
@@ -883,20 +884,6 @@ impl Flow for InlineFlow {
         self.base.floats.translate(Point2D(Au::new(0), -self.base.position.size.height));
     }
 
-    fn collapse_margins(&mut self,
-                        _: bool,
-                        _: &mut bool,
-                        _: &mut Au,
-                        _: &mut Au,
-                        collapsing: &mut Au,
-                        collapsible: &mut Au) {
-        *collapsing = Au::new(0);
-        // Non-empty inline flows prevent collapsing between the previous margion and the next.
-        if self.base.position.size.height > Au::new(0) {
-            *collapsible = Au::new(0);
-        }
-    }
-
     fn debug_str(&self) -> ~str {
         ~"InlineFlow: " + self.boxes.map(|s| s.debug_str()).connect(", ")
     }

src/components/main/layout/layout_task.rs

@@ -11,22 +11,22 @@ use css::select::new_stylist;
 use css::node_style::StyledNode;
 use layout::construct::{FlowConstructionResult, NoConstructionResult};
 use layout::context::LayoutContext;
-use layout::display_list_builder::{DisplayListBuilder, ToGfxColor};
+use layout::display_list_builder::{DisplayListBuilder, DisplayListBuildingInfo, ToGfxColor};
 use layout::flow::{Flow, ImmutableFlowUtils, MutableFlowUtils, MutableOwnedFlowUtils};
 use layout::flow::{PreorderFlowTraversal, PostorderFlowTraversal};
 use layout::flow;
 use layout::incremental::RestyleDamage;
 use layout::parallel::PaddedUnsafeFlow;
 use layout::parallel;
-use layout::util::{LayoutDataAccess, OpaqueNode, LayoutDataWrapper};
+use layout::util::{LayoutDataAccess, LayoutDataWrapper, OpaqueNodeMethods};
 use layout::wrapper::{LayoutNode, TLayoutNode, ThreadSafeLayoutNode};
 
 use extra::url::Url;
 use geom::point::Point2D;
 use geom::rect::Rect;
 use geom::size::Size2D;
-use gfx::display_list::{ClipDisplayItemClass, DisplayItem, DisplayItemIterator};
-use gfx::display_list::{DisplayList, DisplayListCollection};
+use gfx::display_list::{ClipDisplayItemClass, DisplayItem, DisplayItemIterator, DisplayList};
+use gfx::display_list::{OpaqueNode, StackingContext};
 use gfx::font_context::{FontContext, FontContextInfo};
 use gfx::render_task::{RenderMsg, RenderChan, RenderLayer};
 use gfx::{render_task, color};
@@ -41,18 +41,20 @@ use script::layout_interface::{ContentChangedDocumentDamage, LayoutChan, Msg, Pr
 use script::layout_interface::{QueryMsg, ReapLayoutDataMsg, Reflow, UntrustedNodeAddress};
 use script::layout_interface::{ReflowForDisplay, ReflowMsg};
 use script::script_task::{ReflowCompleteMsg, ScriptChan, SendEventMsg};
+use servo_msg::compositor_msg::Scrollable;
 use servo_msg::constellation_msg::{ConstellationChan, PipelineId, Failure, FailureMsg};
 use servo_net::image_cache_task::{ImageCacheTask, ImageResponseMsg};
 use servo_net::local_image_cache::{ImageResponder, LocalImageCache};
 use servo_util::geometry::Au;
+use servo_util::geometry;
 use servo_util::opts::Opts;
+use servo_util::smallvec::{SmallVec, SmallVec0, SmallVec1};
 use servo_util::time::{ProfilerChan, profile};
 use servo_util::time;
 use servo_util::task::send_on_failure;
 use servo_util::workqueue::WorkQueue;
 use std::cast::transmute;
 use std::cast;
-use std::cell::RefCell;
 use std::comm::Port;
 use std::mem;
 use std::ptr;
@@ -79,7 +81,7 @@ pub struct LayoutTask {
     script_chan: ScriptChan,
 
     /// The channel on which messages can be sent to the painting task.
-    render_chan: RenderChan<OpaqueNode>,
+    render_chan: RenderChan,
 
     /// The channel on which messages can be sent to the image cache.
     image_cache_task: ImageCacheTask,
@@ -91,7 +93,7 @@ pub struct LayoutTask {
     screen_size: Size2D<Au>,
 
     /// A cached display list.
-    display_list_collection: Option<Arc<DisplayListCollection<OpaqueNode>>>,
+    display_list: Option<Arc<DisplayList>>,
 
     stylist: ~Stylist,
 
@@ -251,7 +253,7 @@ impl LayoutTask {
                   constellation_chan: ConstellationChan,
                   failure_msg: Failure,
                   script_chan: ScriptChan,
-                  render_chan: RenderChan<OpaqueNode>,
+                  render_chan: RenderChan,
                   img_cache_task: ImageCacheTask,
                   opts: Opts,
                   profiler_chan: ProfilerChan,
@@ -282,7 +284,7 @@ impl LayoutTask {
            chan: LayoutChan,
            constellation_chan: ConstellationChan,
            script_chan: ScriptChan,
-           render_chan: RenderChan<OpaqueNode>,
+           render_chan: RenderChan,
            image_cache_task: ImageCacheTask,
            opts: &Opts,
            profiler_chan: ProfilerChan)
@@ -306,7 +308,7 @@ impl LayoutTask {
             local_image_cache: local_image_cache,
             screen_size: screen_size,
 
-            display_list_collection: None,
+            display_list: None,
             stylist: ~new_stylist(),
             initial_css_values: Arc::new(style::initial_values()),
             parallel_traversal: parallel_traversal,
@@ -339,7 +341,7 @@ impl LayoutTask {
             stylist: &*self.stylist,
             initial_css_values: self.initial_css_values.clone(),
             url: (*url).clone(),
-            reflow_root: OpaqueNode::from_layout_node(reflow_root),
+            reflow_root: OpaqueNodeMethods::from_layout_node(reflow_root),
             opts: self.opts.clone(),
         }
     }
@@ -432,15 +434,13 @@ impl LayoutTask {
             None => fail!("no layout data for root node"),
         };
         let mut flow = match result {
-            FlowConstructionResult(mut flow, abs_descendants, fixed_descendants) => {
+            FlowConstructionResult(mut flow, abs_descendants) => {
                 // Note: Assuming that the root has display 'static' (as per
                 // CSS Section 9.3.1). Otherwise, if it were absolutely
                 // positioned, it would return a reference to itself in
                 // `abs_descendants` and would lead to a circular reference.
                 // Set Root as CB for any remaining absolute descendants.
                 flow.set_abs_descendants(abs_descendants);
-                // Set Root as CB for all fixed descendants.
-                flow.set_fixed_descendants(fixed_descendants);
                 flow
             }
             _ => fail!("Flow construction didn't result in a flow at the root of the tree!"),
@@ -627,26 +627,30 @@ impl LayoutTask {
         // Build the display list if necessary, and send it to the renderer.
         if data.goal == ReflowForDisplay {
             profile(time::LayoutDispListBuildCategory, self.profiler_chan.clone(), || {
-                let root_size = flow::base(layout_root).position.size;
-                let root_abs_position = Point2D(Au::new(0), Au::new(0));
-                let mut display_list_collection = DisplayListCollection::new();
-                display_list_collection.add_list(DisplayList::<OpaqueNode>::new());
-                let display_list_collection = ~RefCell::new(display_list_collection);
-                let dirty = flow::base(layout_root).position.clone();
-                let display_list_builder = DisplayListBuilder {
+                let mut root_stacking_context = StackingContext::new();
+                let mut display_list_builder = DisplayListBuilder {
                     ctx: &layout_ctx,
+                    layers: SmallVec0::new(),
+                    dirty: flow::base(layout_root).position.clone(),
+                };
+                let display_list_building_info = DisplayListBuildingInfo {
+                    relative_containing_block_size: flow::base(layout_root).position.size,
+                    absolute_containing_block_position: Point2D(Au(0), Au(0)),
+                    layers_needed_for_positioned_flows: false,
                 };
-                layout_root.build_display_lists(&display_list_builder, &root_size,
-                                                root_abs_position,
-                                                &dirty, 0u, display_list_collection);
 
-                let display_list_collection = Arc::new(display_list_collection.unwrap());
+                layout_root.build_display_list(&mut root_stacking_context,
+                                               &mut display_list_builder,
+                                               &display_list_building_info);
 
+                let display_list = Arc::new(root_stacking_context.flatten());
+
+                // FIXME(pcwalton): This is really ugly and can't handle overflow: scroll. Refactor
+                // it with extreme prejudice.
                 let mut color = color::rgba(255.0, 255.0, 255.0, 255.0);
-
                 for child in node.traverse_preorder() {
-                    if child.type_id() == ElementNodeTypeId(HTMLHtmlElementTypeId) ||
-                            child.type_id() == ElementNodeTypeId(HTMLBodyElementTypeId) {
+                    if child.type_id() == Some(ElementNodeTypeId(HTMLHtmlElementTypeId)) ||
+                            child.type_id() == Some(ElementNodeTypeId(HTMLBodyElementTypeId)) {
                         let element_bg_color = {
                             let thread_safe_child = ThreadSafeLayoutNode::new(&child);
                             thread_safe_child.style()
@@ -668,18 +672,33 @@ impl LayoutTask {
                     }
                 }
 
+                let root_size = Size2D(display_list_building_info.relative_containing_block_size
+                                                                 .width
+                                                                 .to_nearest_px() as uint,
+                                       display_list_building_info.relative_containing_block_size
+                                                                 .height
+                                                                 .to_nearest_px() as uint);
                 let render_layer = RenderLayer {
-                    display_list_collection: display_list_collection.clone(),
-                    size: Size2D(root_size.width.to_nearest_px() as uint,
-                                 root_size.height.to_nearest_px() as uint),
-                    color: color
+                    id: layout_root.layer_id(0),
+                    display_list: display_list.clone(),
+                    position: Rect(Point2D(0u, 0u), root_size),
+                    background_color: color,
+                    scroll_policy: Scrollable,
                 };
 
-                self.display_list_collection = Some(display_list_collection.clone());
+                self.display_list = Some(display_list.clone());
+
+                let mut layers = SmallVec1::new();
+                layers.push(render_layer);
+                let DisplayListBuilder {
+                    layers: sublayers,
+                    ..
+                } = display_list_builder;
+                layers.push_all_move(sublayers);
 
                 debug!("Layout done!");
 
-                self.render_chan.send(RenderMsg(render_layer));
+                self.render_chan.send(RenderMsg(layers));
             });
         }
 
@@ -701,15 +720,14 @@ impl LayoutTask {
             // The neat thing here is that in order to answer the following two queries we only
             // need to compare nodes for equality. Thus we can safely work only with `OpaqueNode`.
             ContentBoxQuery(node, reply_chan) => {
-                let node = OpaqueNode::from_script_node(node);
+                let node: OpaqueNode = OpaqueNodeMethods::from_script_node(node);
 
-                fn union_boxes_for_node<'a>(
-                                        accumulator: &mut Option<Rect<Au>>,
-                                        mut iter: DisplayItemIterator<'a,OpaqueNode>,
+                fn union_boxes_for_node(accumulator: &mut Option<Rect<Au>>,
+                                        mut iter: DisplayItemIterator,
                                         node: OpaqueNode) {
                     for item in iter {
                         union_boxes_for_node(accumulator, item.children(), node);
-                        if item.base().extra == node {
+                        if item.base().node == node {
                             match *accumulator {
                                 None => *accumulator = Some(item.base().bounds),
                                 Some(ref mut acc) => *acc = acc.union(&item.base().bounds),
@@ -719,41 +737,49 @@ impl LayoutTask {
                 }
 
                 let mut rect = None;
-                for display_list in self.display_list_collection.as_ref().unwrap().get().iter() {
-                    union_boxes_for_node(&mut rect, display_list.iter(), node);
+                match self.display_list {
+                    None => fail!("no display list!"),
+                    Some(ref display_list) => {
+                        union_boxes_for_node(&mut rect, display_list.get().iter(), node)
+                    }
                 }
                 reply_chan.send(ContentBoxResponse(rect.unwrap_or(Au::zero_rect())))
             }
             ContentBoxesQuery(node, reply_chan) => {
-                let node = OpaqueNode::from_script_node(node);
+                let node: OpaqueNode = OpaqueNodeMethods::from_script_node(node);
 
-                fn add_boxes_for_node<'a>(
-                                      accumulator: &mut ~[Rect<Au>],
-                                      mut iter: DisplayItemIterator<'a,OpaqueNode>,
+                fn add_boxes_for_node(accumulator: &mut ~[Rect<Au>],
+                                      mut iter: DisplayItemIterator,
                                       node: OpaqueNode) {
                     for item in iter {
                         add_boxes_for_node(accumulator, item.children(), node);
-                        if item.base().extra == node {
+                        if item.base().node == node {
                             accumulator.push(item.base().bounds)
                         }
                     }
                 }
 
                 let mut boxes = ~[];
-                for display_list in self.display_list_collection.as_ref().unwrap().get().iter() {
-                    add_boxes_for_node(&mut boxes, display_list.iter(), node);
+                match self.display_list {
+                    None => fail!("no display list!"),
+                    Some(ref display_list) => {
+                        add_boxes_for_node(&mut boxes, display_list.get().iter(), node)
+                    }
                 }
                 reply_chan.send(ContentBoxesResponse(boxes))
             }
             HitTestQuery(_, point, reply_chan) => {
-                fn hit_test(x: Au, y: Au, list: &[DisplayItem<OpaqueNode>])
+                fn hit_test(x: Au, y: Au, list: &[DisplayItem])
                             -> Option<HitTestResponse> {
                     for item in list.rev_iter() {
                         match *item {
                             ClipDisplayItemClass(ref cc) => {
-                                let ret = hit_test(x, y, cc.child_list);
-                                if !ret.is_none() {
-                                    return ret;
+                                if !cc.need_clip || geometry::rect_contains_point(cc.base.bounds,
+                                                                                  Point2D(x, y)) {
+                                    let ret = hit_test(x, y, cc.child_list.as_slice());
+                                    if !ret.is_none() {
+                                        return ret
+                                    }
                                 }
                             }
                             _ => {}
@@ -774,31 +800,35 @@ impl LayoutTask {
                                 y < bounds.origin.y + bounds.size.height &&
                                 bounds.origin.y <= y {
                             return Some(HitTestResponse(item.base()
-                                                            .extra
+                                                            .node
                                                             .to_untrusted_node_address()))
                         }
                     }
                     let ret: Option<HitTestResponse> = None;
                     ret
                 }
-                for display_list in self.display_list_collection.as_ref().unwrap().get().lists.rev_iter() {
-                    let (x, y) = (Au::from_frac_px(point.x as f64),
-                                  Au::from_frac_px(point.y as f64));
-                    let resp = hit_test(x,y,display_list.list);
-                    if resp.is_some() {
-                        reply_chan.send(Ok(resp.unwrap()));
-                        return
-                    }
+                let (x, y) = (Au::from_frac_px(point.x as f64),
+                              Au::from_frac_px(point.y as f64));
+                let resp = match self.display_list {
+                    None => fail!("no display list!"),
+                    Some(ref display_list) => hit_test(x, y, display_list.get().list.as_slice()),
+                };
+                if resp.is_some() {
+                    reply_chan.send(Ok(resp.unwrap()));
+                    return
                 }
                 reply_chan.send(Err(()));
 
             }
             MouseOverQuery(_, point, reply_chan) => {
-                fn mouse_over_test(x: Au, y: Au, list: &[DisplayItem<OpaqueNode>], result: &mut ~[UntrustedNodeAddress]) {
+                fn mouse_over_test(x: Au,
+                                   y: Au,
+                                   list: &[DisplayItem],
+                                   result: &mut ~[UntrustedNodeAddress]) {
                     for item in list.rev_iter() {
                         match *item {
                             ClipDisplayItemClass(ref cc) => {
-                                mouse_over_test(x, y, cc.child_list, result);
+                                mouse_over_test(x, y, cc.child_list.as_slice(), result);
                             }
                             _ => {}
                         }
@@ -814,18 +844,24 @@ impl LayoutTask {
                                 y < bounds.origin.y + bounds.size.height &&
                                 bounds.origin.y <= y {
                             result.push(item.base()
-                                            .extra
+                                            .node
                                             .to_untrusted_node_address());
                         }
                     }
                 }
 
                 let mut mouse_over_list:~[UntrustedNodeAddress] = ~[];
-                for display_list in self.display_list_collection.as_ref().unwrap().get().lists.rev_iter() {
-                    let (x, y) = (Au::from_frac_px(point.x as f64),
-                                  Au::from_frac_px(point.y as f64));
-                    mouse_over_test(x,y,display_list.list, &mut mouse_over_list);
-                }
+                let (x, y) = (Au::from_frac_px(point.x as f64),
+                              Au::from_frac_px(point.y as f64));
+                match self.display_list {
+                    None => fail!("no display list!"),
+                    Some(ref display_list) => {
+                        mouse_over_test(x,
+                                        y,
+                                        display_list.get().list.as_slice(),
+                                        &mut mouse_over_list);
+                    }
+                };
 
                 if mouse_over_list.is_empty() {
                     reply_chan.send(Err(()));

src/components/main/layout/model.rs

@@ -4,8 +4,257 @@
 
 //! Borders, padding, and margins.
 
-use servo_util::geometry::Au;
+use layout::box_::Box;
+
 use computed = style::computed_values;
+use style::computed_values::{LPA_Auto, LPA_Length, LPA_Percentage};
+use servo_util::geometry::Au;
+use servo_util::geometry;
+
+/// A collapsible margin. See CSS 2.1 § 8.3.1.
+pub struct AdjoiningMargins {
+    /// The value of the greatest positive margin.
+    most_positive: Au,
+
+    /// The actual value (not the absolute value) of the negative margin with the largest absolute
+    /// value. Since this is not the absolute value, this is always zero or negative.
+    most_negative: Au,
+}
+
+impl AdjoiningMargins {
+    pub fn new() -> AdjoiningMargins {
+        AdjoiningMargins {
+            most_positive: Au(0),
+            most_negative: Au(0),
+        }
+    }
+
+    pub fn from_margin(margin_value: Au) -> AdjoiningMargins {
+        if margin_value >= Au(0) {
+            AdjoiningMargins {
+                most_positive: margin_value,
+                most_negative: Au(0),
+            }
+        } else {
+            AdjoiningMargins {
+                most_positive: Au(0),
+                most_negative: margin_value,
+            }
+        }
+    }
+
+    pub fn union(&mut self, other: AdjoiningMargins) {
+        self.most_positive = geometry::max(self.most_positive, other.most_positive);
+        self.most_negative = geometry::min(self.most_negative, other.most_negative)
+    }
+
+    pub fn collapse(&self) -> Au {
+        self.most_positive + self.most_negative
+    }
+}
+
+/// Represents the top and bottom margins of a flow with collapsible margins. See CSS 2.1 § 8.3.1.
+pub enum CollapsibleMargins {
+    /// Margins may not collapse with this flow.
+    NoCollapsibleMargins(Au, Au),
+
+    /// Both the top and bottom margins (specified here in that order) may collapse, but the
+    /// margins do not collapse through this flow.
+    MarginsCollapse(AdjoiningMargins, AdjoiningMargins),
+
+    /// Margins collapse *through* this flow. This means, essentially, that the flow doesn’t
+    /// have any border, padding, or out-of-flow (floating or positioned) content
+    MarginsCollapseThrough(AdjoiningMargins),
+}
+
+impl CollapsibleMargins {
+    pub fn new() -> CollapsibleMargins {
+        NoCollapsibleMargins(Au(0), Au(0))
+    }
+}
+
+enum FinalMarginState {
+    MarginsCollapseThroughFinalMarginState,
+    BottomMarginCollapsesFinalMarginState,
+}
+
+pub struct MarginCollapseInfo {
+    state: MarginCollapseState,
+    top_margin: AdjoiningMargins,
+    margin_in: AdjoiningMargins,
+}
+
+impl MarginCollapseInfo {
+    /// TODO(#2012, pcwalton): Remove this method once `box_` is not an `Option`.
+    pub fn new() -> MarginCollapseInfo {
+        MarginCollapseInfo {
+            state: AccumulatingCollapsibleTopMargin,
+            top_margin: AdjoiningMargins::new(),
+            margin_in: AdjoiningMargins::new(),
+        }
+    }
+
+    pub fn initialize_top_margin(&mut self,
+                                 fragment: &Box,
+                                 can_collapse_top_margin_with_kids: bool) {
+        if !can_collapse_top_margin_with_kids {
+            self.state = AccumulatingMarginIn
+        }
+
+        self.top_margin = AdjoiningMargins::from_margin(fragment.margin.get().top)
+    }
+
+    pub fn finish_and_compute_collapsible_margins(mut self,
+                                                  fragment: &Box,
+                                                  can_collapse_bottom_margin_with_kids: bool)
+                                                  -> (CollapsibleMargins, Au) {
+        let state = match self.state {
+            AccumulatingCollapsibleTopMargin => {
+                match fragment.style().Box.get().height {
+                    LPA_Auto | LPA_Length(Au(0)) | LPA_Percentage(0.) => {
+                        MarginsCollapseThroughFinalMarginState
+                    },
+                    _ => {
+                        // If the box has an explicitly specified height, margins may not collapse
+                        // through it.
+                        BottomMarginCollapsesFinalMarginState
+                    }
+                }
+            }
+            AccumulatingMarginIn => BottomMarginCollapsesFinalMarginState,
+        };
+
+        // Different logic is needed here depending on whether this flow can collapse its bottom
+        // margin with its children.
+        let bottom_margin = fragment.margin.get().bottom;
+        if !can_collapse_bottom_margin_with_kids {
+            match state {
+                MarginsCollapseThroughFinalMarginState => {
+                    let advance = self.top_margin.collapse();
+                    self.margin_in.union(AdjoiningMargins::from_margin(bottom_margin));
+                    (MarginsCollapse(self.top_margin, self.margin_in), advance)
+                }
+                BottomMarginCollapsesFinalMarginState => {
+                    let advance = self.margin_in.collapse();
+                    self.margin_in.union(AdjoiningMargins::from_margin(bottom_margin));
+                    (MarginsCollapse(self.top_margin, self.margin_in), advance)
+                }
+            }
+        } else {
+            match state {
+                MarginsCollapseThroughFinalMarginState => {
+                    self.top_margin.union(AdjoiningMargins::from_margin(bottom_margin));
+                    (MarginsCollapseThrough(self.top_margin), Au(0))
+                }
+                BottomMarginCollapsesFinalMarginState => {
+                    self.margin_in.union(AdjoiningMargins::from_margin(bottom_margin));
+                    (MarginsCollapse(self.top_margin, self.margin_in), Au(0))
+                }
+            }
+        }
+    }
+
+    pub fn current_float_ceiling(&mut self) -> Au {
+        match self.state {
+            AccumulatingCollapsibleTopMargin => self.top_margin.collapse(),
+            AccumulatingMarginIn => self.margin_in.collapse(),
+        }
+    }
+
+    /// Adds the child's potentially collapsible top margin to the current margin state and
+    /// advances the Y offset by the appropriate amount to handle that margin. Returns the amount
+    /// that should be added to the Y offset during block layout.
+    pub fn advance_top_margin(&mut self, child_collapsible_margins: &CollapsibleMargins) -> Au {
+        match (self.state, *child_collapsible_margins) {
+            (AccumulatingCollapsibleTopMargin, NoCollapsibleMargins(top, _)) => {
+                self.state = AccumulatingMarginIn;
+                top
+            }
+            (AccumulatingCollapsibleTopMargin, MarginsCollapse(top, _)) => {
+                self.top_margin.union(top);
+                self.state = AccumulatingMarginIn;
+                Au(0)
+            }
+            (AccumulatingMarginIn, NoCollapsibleMargins(top, _)) => {
+                let previous_margin_value = self.margin_in.collapse();
+                self.margin_in = AdjoiningMargins::new();
+                previous_margin_value + top
+            }
+            (AccumulatingMarginIn, MarginsCollapse(top, _)) => {
+                self.margin_in.union(top);
+                let margin_value = self.margin_in.collapse();
+                self.margin_in = AdjoiningMargins::new();
+                margin_value
+            }
+            (_, MarginsCollapseThrough(_)) => {
+                // For now, we ignore this; this will be handled by `advance_bottom_margin` below.
+                Au(0)
+            }
+        }
+    }
+
+    /// Adds the child's potentially collapsible bottom margin to the current margin state and
+    /// advances the Y offset by the appropriate amount to handle that margin. Returns the amount
+    /// that should be added to the Y offset during block layout.
+    pub fn advance_bottom_margin(&mut self, child_collapsible_margins: &CollapsibleMargins) -> Au {
+        match (self.state, *child_collapsible_margins) {
+            (AccumulatingCollapsibleTopMargin, NoCollapsibleMargins(..)) |
+            (AccumulatingCollapsibleTopMargin, MarginsCollapse(..)) => {
+                // Can't happen because the state will have been replaced with
+                // `AccumulatingMarginIn` above.
+                fail!("should not be accumulating collapsible top margins anymore!")
+            }
+            (AccumulatingCollapsibleTopMargin, MarginsCollapseThrough(margin)) => {
+                self.top_margin.union(margin);
+                Au(0)
+            }
+            (AccumulatingMarginIn, NoCollapsibleMargins(_, bottom)) => {
+                assert_eq!(self.margin_in.most_positive, Au(0));
+                assert_eq!(self.margin_in.most_negative, Au(0));
+                bottom
+            }
+            (AccumulatingMarginIn, MarginsCollapse(_, bottom)) |
+            (AccumulatingMarginIn, MarginsCollapseThrough(bottom)) => {
+                self.margin_in.union(bottom);
+                Au(0)
+            }
+        }
+    }
+}
+
+enum MarginCollapseState {
+    AccumulatingCollapsibleTopMargin,
+    AccumulatingMarginIn,
+}
+
+/// Intrinsic widths, which consist of minimum and preferred.
+pub struct IntrinsicWidths {
+    /// The *minimum width* of the content.
+    minimum_width: Au,
+    /// The *preferred width* of the content.
+    preferred_width: Au,
+    /// The estimated sum of borders, padding, and margins. Some calculations use this information
+    /// when computing intrinsic widths.
+    surround_width: Au,
+}
+
+impl IntrinsicWidths {
+    pub fn new() -> IntrinsicWidths {
+        IntrinsicWidths {
+            minimum_width: Au(0),
+            preferred_width: Au(0),
+            surround_width: Au(0),
+        }
+    }
+
+    pub fn total_minimum_width(&self) -> Au {
+        self.minimum_width + self.surround_width
+    }
+
+    pub fn total_preferred_width(&self) -> Au {
+        self.preferred_width + self.surround_width
+    }
+}
 
 /// Useful helper data type when computing values for blocks and positioned elements.
 pub enum MaybeAuto {

src/components/main/layout/parallel.rs

@@ -14,10 +14,11 @@ use layout::flow::{Flow, PreorderFlowTraversal, PostorderFlowTraversal};
 use layout::flow;
 use layout::layout_task::{AssignHeightsAndStoreOverflowTraversal, AssignWidthsTraversal};
 use layout::layout_task::{BubbleWidthsTraversal};
-use layout::util::{LayoutDataAccess, OpaqueNode};
+use layout::util::{LayoutDataAccess, OpaqueNodeMethods};
 use layout::wrapper::{layout_node_to_unsafe_layout_node, LayoutNode, PostorderNodeMutTraversal};
 use layout::wrapper::{ThreadSafeLayoutNode, UnsafeLayoutNode};
 
+use gfx::display_list::OpaqueNode;
 use servo_util::time::{ProfilerChan, profile};
 use servo_util::time;
 use servo_util::workqueue::{WorkQueue, WorkUnit, WorkerProxy};
@@ -244,7 +245,8 @@ fn recalc_style_for_node(unsafe_layout_node: UnsafeLayoutNode,
         node.initialize_layout_data(layout_context.layout_chan.clone());
 
         // Get the parent node.
-        let parent_opt = if OpaqueNode::from_layout_node(&node) == layout_context.reflow_root {
+        let opaque_node: OpaqueNode = OpaqueNodeMethods::from_layout_node(&node);
+        let parent_opt = if opaque_node == layout_context.reflow_root {
             None
         } else {
             node.parent_node()
@@ -345,7 +347,8 @@ fn construct_flows(mut unsafe_layout_node: UnsafeLayoutNode,
         }
 
         // If this is the reflow root, we're done.
-        if layout_context.reflow_root == OpaqueNode::from_layout_node(&node) {
+        let opaque_node: OpaqueNode = OpaqueNodeMethods::from_layout_node(&node);
+        if layout_context.reflow_root == opaque_node {
             break
         }
 

src/components/main/layout/table.rs

@@ -5,22 +5,21 @@
 //! CSS table formatting contexts.
 
 use layout::box_::Box;
-use layout::block::BlockFlow;
-use layout::block::{WidthAndMarginsComputer, WidthConstraintInput, WidthConstraintSolution};
+use layout::block::{BlockFlow, MarginsMayNotCollapse, WidthAndMarginsComputer};
+use layout::block::{WidthConstraintInput, WidthConstraintSolution};
 use layout::construct::FlowConstructor;
 use layout::context::LayoutContext;
-use layout::display_list_builder::{DisplayListBuilder, ExtraDisplayListData};
+use layout::display_list_builder::{DisplayListBuilder, DisplayListBuildingInfo};
 use layout::floats::{FloatKind};
 use layout::flow::{TableFlowClass, FlowClass, Flow, ImmutableFlowUtils};
 use layout::flow;
 use layout::table_wrapper::{TableLayout, FixedLayout, AutoLayout};
 use layout::wrapper::ThreadSafeLayoutNode;
 
-use std::cell::RefCell;
-use style::computed_values::table_layout;
-use geom::{Point2D, Rect, Size2D};
-use gfx::display_list::DisplayListCollection;
+use gfx::display_list::StackingContext;
 use servo_util::geometry::Au;
+use servo_util::geometry;
+use style::computed_values::table_layout;
 
 /// A table flow corresponded to the table's internal table box under a table wrapper flow.
 /// The properties `position`, `float`, and `margin-*` are used on the table wrapper box,
@@ -31,6 +30,12 @@ pub struct TableFlow {
     /// Column widths
     col_widths: ~[Au],
 
+    /// Column min widths.
+    col_min_widths: ~[Au],
+
+    /// Column pref widths.
+    col_pref_widths: ~[Au],
+
     /// Table-layout property
     table_layout: TableLayout,
 }
@@ -49,6 +54,8 @@ impl TableFlow {
         TableFlow {
             block_flow: block_flow,
             col_widths: ~[],
+            col_min_widths: ~[],
+            col_pref_widths: ~[],
             table_layout: table_layout
         }
     }
@@ -66,6 +73,8 @@ impl TableFlow {
         TableFlow {
             block_flow: block_flow,
             col_widths: ~[],
+            col_min_widths: ~[],
+            col_pref_widths: ~[],
             table_layout: table_layout
         }
     }
@@ -84,6 +93,8 @@ impl TableFlow {
         TableFlow {
             block_flow: block_flow,
             col_widths: ~[],
+            col_min_widths: ~[],
+            col_pref_widths: ~[],
             table_layout: table_layout
         }
     }
@@ -91,61 +102,46 @@ impl TableFlow {
     pub fn teardown(&mut self) {
         self.block_flow.teardown();
         self.col_widths = ~[];
+        self.col_min_widths = ~[];
+        self.col_pref_widths = ~[];
+    }
+
+    /// Update the corresponding value of self_widths if a value of kid_widths has larger value
+    /// than one of self_widths.
+    pub fn update_col_widths(self_widths: &mut ~[Au], kid_widths: &~[Au]) -> Au {
+        let mut sum_widths = Au(0);
+        let mut kid_widths_it = kid_widths.iter();
+        for self_width in self_widths.mut_iter() {
+            match kid_widths_it.next() {
+                Some(kid_width) => {
+                    if *self_width < *kid_width {
+                        *self_width = *kid_width;
+                    }
+                },
+                None => {}
+            }
+            sum_widths = sum_widths + *self_width;
+        }
+        sum_widths
     }
 
     /// Assign height for table flow.
     ///
+    /// TODO(#2014, pcwalton): This probably doesn't handle margin collapse right.
+    ///
     /// inline(always) because this is only ever called by in-order or non-in-order top-level
     /// methods
     #[inline(always)]
-    fn assign_height_table_base(&mut self, ctx: &mut LayoutContext, inorder: bool) {
-
-        let (_, top_offset, bottom_offset, left_offset) = self.block_flow.initialize_offsets(true);
-
-        self.block_flow.handle_children_floats_if_necessary(ctx, inorder,
-                                                            left_offset, top_offset);
-
-        let mut cur_y = top_offset;
-        for kid in self.block_flow.base.child_iter() {
-            let child_node = flow::mut_base(kid);
-            child_node.position.origin.y = cur_y;
-            cur_y = cur_y + child_node.position.size.height;
-        }
-
-        let height = cur_y - top_offset;
-
-        let mut noncontent_height = Au::new(0);
-        for box_ in self.block_flow.box_.iter() {
-            let mut position = box_.border_box.get();
-
-            // noncontent_height = border_top/bottom + padding_top/bottom of box
-            noncontent_height = box_.noncontent_height();
-
-            position.origin.y = Au(0);
-            position.size.height = height + noncontent_height;
-
-            box_.border_box.set(position);
-        }
-
-        self.block_flow.base.position.size.height = height + noncontent_height;
-
-        self.block_flow.set_floats_out_if_inorder(inorder, height, cur_y,
-                                                  top_offset, bottom_offset, left_offset);
+    fn assign_height_table_base(&mut self, layout_context: &mut LayoutContext, inorder: bool) {
+        self.block_flow.assign_height_block_base(layout_context, inorder, MarginsMayNotCollapse);
     }
 
-    pub fn build_display_list_table<E:ExtraDisplayListData>(
-                                    &mut self,
-                                    builder: &DisplayListBuilder,
-                                    container_block_size: &Size2D<Au>,
-                                    absolute_cb_abs_position: Point2D<Au>,
-                                    dirty: &Rect<Au>,
-                                    index: uint,
-                                    lists: &RefCell<DisplayListCollection<E>>)
-                                    -> uint {
+    pub fn build_display_list_table(&mut self,
+                                    stacking_context: &mut StackingContext,
+                                    builder: &mut DisplayListBuilder,
+                                    info: &DisplayListBuildingInfo) {
         debug!("build_display_list_table: same process as block flow");
-        self.block_flow.build_display_list_block(builder, container_block_size,
-                                                 absolute_cb_abs_position,
-                                                 dirty, index, lists)
+        self.block_flow.build_display_list_block(stacking_context, builder, info);
     }
 }
 
@@ -162,54 +158,95 @@ impl Flow for TableFlow {
         &mut self.block_flow
     }
 
-    /// This function finds the specified column widths from column group and the first row.
-    /// Those are used in fixed table layout calculation.
-    /* FIXME: automatic table layout calculation */
-    fn bubble_widths(&mut self, ctx: &mut LayoutContext) {
-        let mut did_first_row = false;
+    fn col_widths<'a>(&'a mut self) -> &'a mut ~[Au] {
+        &mut self.col_widths
+    }
+
+    fn col_min_widths<'a>(&'a self) -> &'a ~[Au] {
+        &self.col_min_widths
+    }
+
+    fn col_pref_widths<'a>(&'a self) -> &'a ~[Au] {
+        &self.col_pref_widths
+    }
+
+    /// The specified column widths are set from column group and the first row for the fixed
+    /// table layout calculation.
+    /// The maximum min/pref widths of each column are set from the rows for the automatic
+    /// table layout calculation.
+    fn bubble_widths(&mut self, _: &mut LayoutContext) {
+        let mut min_width = Au(0);
+        let mut pref_width = Au(0);
+        let mut did_first_row = false;
+        let mut num_floats = 0;
 
-        /* find max width from child block contexts */
         for kid in self.block_flow.base.child_iter() {
             assert!(kid.is_proper_table_child());
 
             if kid.is_table_colgroup() {
                 self.col_widths.push_all(kid.as_table_colgroup().widths);
+                self.col_min_widths = self.col_widths.clone();
+                self.col_pref_widths = self.col_widths.clone();
             } else if kid.is_table_rowgroup() || kid.is_table_row() {
                 // read column widths from table-row-group/table-row, and assign
                 // width=0 for the columns not defined in column-group
                 // FIXME: need to read widths from either table-header-group OR
                 // first table-row
-                let kid_col_widths = if kid.is_table_rowgroup() {
-                    &kid.as_table_rowgroup().col_widths
-                } else {
-                    &kid.as_table_row().col_widths
-                };
                 match self.table_layout {
-                    FixedLayout if !did_first_row => {
-                        did_first_row = true;
-                        let mut child_widths = kid_col_widths.iter();
-                        for col_width in self.col_widths.mut_iter() {
-                            match child_widths.next() {
-                                Some(child_width) => {
-                                    if *col_width == Au::new(0) {
-                                        *col_width = *child_width;
-                                    }
-                                },
-                                None => break
+                    FixedLayout => {
+                        let kid_col_widths = kid.col_widths();
+                        if !did_first_row {
+                            did_first_row = true;
+                            let mut child_widths = kid_col_widths.iter();
+                            for col_width in self.col_widths.mut_iter() {
+                                match child_widths.next() {
+                                    Some(child_width) => {
+                                        if *col_width == Au::new(0) {
+                                            *col_width = *child_width;
+                                        }
+                                    },
+                                    None => break
+                                }
                             }
                         }
+                        let num_child_cols = kid_col_widths.len();
+                        let num_cols = self.col_widths.len();
+                        debug!("table until the previous row has {} column(s) and this row has {} column(s)",
+                               num_cols, num_child_cols);
+                        for i in range(num_cols, num_child_cols) {
+                            self.col_widths.push( kid_col_widths[i] );
+                        }
                     },
-                    _ => {}
-                }
-                let num_child_cols = kid_col_widths.len();
-                let num_cols = self.col_widths.len();
-                debug!("colgroup has {} column(s) and child has {} column(s)", num_cols, num_child_cols);
-                for i in range(num_cols, num_child_cols) {
-                    self.col_widths.push( kid_col_widths[i] );
+                    AutoLayout => {
+                        min_width = TableFlow::update_col_widths(&mut self.col_min_widths, kid.col_min_widths());
+                        pref_width = TableFlow::update_col_widths(&mut self.col_pref_widths, kid.col_pref_widths());
+
+                        // update the number of column widths from table-rows.
+                        let num_cols = self.col_min_widths.len();
+                        let num_child_cols = kid.col_min_widths().len();
+                        debug!("table until the previous row has {} column(s) and this row has {} column(s)",
+                               num_cols, num_child_cols);
+                        for i in range(num_cols, num_child_cols) {
+                            self.col_widths.push(Au::new(0));
+                            let new_kid_min = kid.col_min_widths()[i];
+                            self.col_min_widths.push( new_kid_min );
+                            let new_kid_pref = kid.col_pref_widths()[i];
+                            self.col_pref_widths.push( new_kid_pref );
+                            min_width = min_width + new_kid_min;
+                            pref_width = pref_width + new_kid_pref;
+                        }
+                    }
                 }
             }
+            let child_base = flow::mut_base(kid);
+            num_floats = num_floats + child_base.num_floats;
         }
-        self.block_flow.bubble_widths(ctx);
+        for box_ in self.block_flow.box_.iter() {
+            box_.compute_borders(box_.style());
+        }
+        self.block_flow.base.num_floats = num_floats;
+        self.block_flow.base.intrinsic_widths.minimum_width = min_width;
+        self.block_flow.base.intrinsic_widths.preferred_width = geometry::max(min_width, pref_width);
     }
 
     /// Recursively (top-down) determines the actual width of child contexts and boxes. When called
@@ -242,20 +279,25 @@ impl Flow for TableFlow {
             content_width = box_.border_box.get().size.width - padding_and_borders;
         }
 
-        // In fixed table layout, we distribute extra space among the unspecified columns if there are
-        // any, or among all the columns if all are specified.
-        if (total_column_width < content_width) && (num_unspecified_widths == 0) {
-            let ratio = content_width.to_f64().unwrap() / total_column_width.to_f64().unwrap();
-            for col_width in self.col_widths.mut_iter() {
-                *col_width = (*col_width).scale_by(ratio);
-            }
-        } else if num_unspecified_widths != 0 {
-            let extra_column_width = (content_width - total_column_width) / Au::new(num_unspecified_widths);
-            for col_width in self.col_widths.mut_iter() {
-                if *col_width == Au(0) {
-                    *col_width = extra_column_width;
+        match self.table_layout {
+            FixedLayout => {
+                // In fixed table layout, we distribute extra space among the unspecified columns if there are
+                // any, or among all the columns if all are specified.
+                if (total_column_width < content_width) && (num_unspecified_widths == 0) {
+                    let ratio = content_width.to_f64().unwrap() / total_column_width.to_f64().unwrap();
+                    for col_width in self.col_widths.mut_iter() {
+                        *col_width = (*col_width).scale_by(ratio);
+                    }
+                } else if num_unspecified_widths != 0 {
+                    let extra_column_width = (content_width - total_column_width) / Au::new(num_unspecified_widths);
+                    for col_width in self.col_widths.mut_iter() {
+                        if *col_width == Au(0) {
+                            *col_width = extra_column_width;
+                        }
+                    }
                 }
             }
+            _ => {}
         }
 
         self.block_flow.propagate_assigned_width_to_children(left_content_edge, content_width, Some(self.col_widths.clone()));
@@ -275,20 +317,6 @@ impl Flow for TableFlow {
         self.assign_height_table_base(ctx, false);
     }
 
-    // CSS Section 8.3.1 - Collapsing Margins
-    // Since `margin` is not used on table box, `collapsing` and `collapsible` are set to 0
-    fn collapse_margins(&mut self,
-                        _: bool,
-                        _: &mut bool,
-                        _: &mut Au,
-                        _: &mut Au,
-                        collapsing: &mut Au,
-                        collapsible: &mut Au) {
-        // `margin` is not used on table box.
-        *collapsing = Au::new(0);
-        *collapsible = Au::new(0);
-    }
-
     fn debug_str(&self) -> ~str {
         let txt = ~"TableFlow: ";
         txt.append(match self.block_flow.box_ {

src/components/main/layout/table_caption.rs

@@ -7,14 +7,11 @@
 use layout::block::BlockFlow;
 use layout::construct::FlowConstructor;
 use layout::context::LayoutContext;
-use layout::display_list_builder::{DisplayListBuilder, ExtraDisplayListData};
+use layout::display_list_builder::{DisplayListBuilder, DisplayListBuildingInfo};
 use layout::flow::{TableCaptionFlowClass, FlowClass, Flow};
 use layout::wrapper::ThreadSafeLayoutNode;
 
-use std::cell::RefCell;
-use geom::{Point2D, Rect, Size2D};
-use gfx::display_list::DisplayListCollection;
-use servo_util::geometry::Au;
+use gfx::display_list::StackingContext;
 
 /// A table formatting context.
 pub struct TableCaptionFlow {
@@ -34,19 +31,12 @@ impl TableCaptionFlow {
         self.block_flow.teardown();
     }
 
-    pub fn build_display_list_table_caption<E:ExtraDisplayListData>(
-                                           &mut self,
-                                           builder: &DisplayListBuilder,
-                                           container_block_size: &Size2D<Au>,
-                                           absolute_cb_abs_position: Point2D<Au>,
-                                           dirty: &Rect<Au>,
-                                           index: uint,
-                                           lists: &RefCell<DisplayListCollection<E>>)
-                                           -> uint {
+    pub fn build_display_list_table_caption(&mut self,
+                                            stacking_context: &mut StackingContext,
+                                            builder: &mut DisplayListBuilder,
+                                            info: &DisplayListBuildingInfo) {
         debug!("build_display_list_table_caption: same process as block flow");
-        self.block_flow.build_display_list_block(builder, container_block_size,
-                                                 absolute_cb_abs_position,
-                                                 dirty, index, lists)
+        self.block_flow.build_display_list_block(stacking_context, builder, info)
     }
 }
 
@@ -86,13 +76,6 @@ impl Flow for TableCaptionFlow {
         self.block_flow.assign_height(ctx);
     }
 
-    /// table-caption has margins but is not collapsed with a sibling(table)
-    /// or its parents(table-wrapper).
-    /// Therefore, margins to be collapsed do not exist.
-    fn collapse_margins(&mut self, _: bool, _: &mut bool, _: &mut Au,
-                        _: &mut Au, _: &mut Au, _: &mut Au) {
-    }
-
     fn debug_str(&self) -> ~str {
         let txt = ~"TableCaptionFlow: ";
         txt.append(match self.block_flow.box_ {

src/components/main/layout/table_cell.rs

@@ -5,16 +5,15 @@
 //! CSS table formatting contexts.
 
 use layout::box_::Box;
-use layout::block::{BlockFlow, WidthAndMarginsComputer};
+use layout::block::{BlockFlow, MarginsMayNotCollapse, WidthAndMarginsComputer};
 use layout::context::LayoutContext;
-use layout::display_list_builder::{DisplayListBuilder, ExtraDisplayListData};
+use layout::display_list_builder::{DisplayListBuilder, DisplayListBuildingInfo};
 use layout::flow::{TableCellFlowClass, FlowClass, Flow};
+use layout::model::{MaybeAuto};
 use layout::table::InternalTable;
 use layout::wrapper::ThreadSafeLayoutNode;
 
-use std::cell::RefCell;
-use geom::{Point2D, Rect, Size2D};
-use gfx::display_list::{DisplayListCollection};
+use gfx::display_list::StackingContext;
 use servo_util::geometry::Au;
 
 /// A table formatting context.
@@ -42,62 +41,23 @@ impl TableCellFlow {
 
     /// Assign height for table-cell flow.
     ///
+    /// TODO(#2015, pcwalton): This doesn't handle floats right.
+    ///
     /// inline(always) because this is only ever called by in-order or non-in-order top-level
     /// methods
     #[inline(always)]
-    fn assign_height_table_cell_base(&mut self, ctx: &mut LayoutContext, inorder: bool) {
-        let (_, mut top_offset, bottom_offset, left_offset) = self.block_flow
-                                                                  .initialize_offsets(true);
-
-        self.block_flow.handle_children_floats_if_necessary(ctx, inorder,
-                                                            left_offset, top_offset);
-        let mut cur_y = top_offset;
-        // Since table cell does not have `margin`, the first child's top margin and
-        // the last child's bottom margin do not collapse.
-        self.block_flow.compute_margin_collapse(&mut cur_y,
-                                                &mut top_offset,
-                                                &mut Au(0),
-                                                &mut Au(0),
-                                                false,
-                                                false);
-
-        // CSS 2.1 § 17.5.3. Table cell box height is the minimum height required by the content.
-        let height = cur_y - top_offset;
-
-        // TODO(june0cho): vertical-align of table-cell should be calculated.
-        let mut noncontent_height = Au::new(0);
-        for box_ in self.block_flow.box_.iter() {
-            let mut position = box_.border_box.get();
-
-            // noncontent_height = border_top/bottom + padding_top/bottom of box
-            noncontent_height = box_.noncontent_height();
-
-            position.origin.y = Au(0);
-            position.size.height = height + noncontent_height;
-
-            box_.border_box.set(position);
-        }
-
-        self.block_flow.base.position.size.height = height + noncontent_height;
-
-        self.block_flow.set_floats_out_if_inorder(inorder, height, cur_y, top_offset,
-                                                  bottom_offset, left_offset);
-        self.block_flow.assign_height_absolute_flows(ctx);
+    fn assign_height_table_cell_base(&mut self,
+                                     layout_context: &mut LayoutContext,
+                                     inorder: bool) {
+        self.block_flow.assign_height_block_base(layout_context, inorder, MarginsMayNotCollapse)
     }
 
-    pub fn build_display_list_table_cell<E:ExtraDisplayListData>(
-                                           &mut self,
-                                           builder: &DisplayListBuilder,
-                                           container_block_size: &Size2D<Au>,
-                                           absolute_cb_abs_position: Point2D<Au>,
-                                           dirty: &Rect<Au>,
-                                           index: uint,
-                                           lists: &RefCell<DisplayListCollection<E>>)
-                                           -> uint {
-        debug!("build_display_list_table_cell: same process as block flow");
-        self.block_flow.build_display_list_block(builder, container_block_size,
-                                                 absolute_cb_abs_position,
-                                                 dirty, index, lists)
+    pub fn build_display_list_table_cell(&mut self,
+                                         stacking_context: &mut StackingContext,
+                                         builder: &mut DisplayListBuilder,
+                                         info: &DisplayListBuildingInfo) {
+        debug!("build_display_list_table: same process as block flow");
+        self.block_flow.build_display_list_block(stacking_context, builder, info)
     }
 }
 
@@ -117,6 +77,18 @@ impl Flow for TableCellFlow {
     /// Minimum/preferred widths set by this function are used in automatic table layout calculation.
     fn bubble_widths(&mut self, ctx: &mut LayoutContext) {
         self.block_flow.bubble_widths(ctx);
+        for box_ in self.block_flow.box_.iter() {
+            let specified_width = MaybeAuto::from_style(box_.style().Box.get().width,
+                                                        Au::new(0)).specified_or_zero();
+            if self.block_flow.base.intrinsic_widths.minimum_width < specified_width {
+                self.block_flow.base.intrinsic_widths.minimum_width = specified_width;
+            }
+            if self.block_flow.base.intrinsic_widths.preferred_width <
+                    self.block_flow.base.intrinsic_widths.minimum_width {
+                self.block_flow.base.intrinsic_widths.preferred_width =
+                    self.block_flow.base.intrinsic_widths.minimum_width;
+            }
+        }
     }
 
     /// Recursively (top-down) determines the actual width of child contexts and boxes. When called
@@ -156,12 +128,6 @@ impl Flow for TableCellFlow {
         self.assign_height_table_cell_base(ctx, false);
     }
 
-    /// TableCellBox and their parents(TableRowBox) do not have margins.
-    /// Therefore, margins to be collapsed do not exist.
-    fn collapse_margins(&mut self, _: bool, _: &mut bool, _: &mut Au,
-                        _: &mut Au, _: &mut Au, _: &mut Au) {
-    }
-
     fn debug_str(&self) -> ~str {
         let txt = ~"TableCellFlow: ";
         txt.append(match self.block_flow.box_ {

src/components/main/layout/table_colgroup.rs

@@ -82,12 +82,6 @@ impl Flow for TableColGroupFlow {
     fn assign_height(&mut self, _ctx: &mut LayoutContext) {
     }
 
-    /// TableColumnBox and their parents(TableBox) do not have margins.
-    /// Therefore, margins to be collapsed do not exist.
-    fn collapse_margins(&mut self, _: bool, _: &mut bool, _: &mut Au,
-                        _: &mut Au, _: &mut Au, _: &mut Au) {
-    }
-
     fn debug_str(&self) -> ~str {
         let txt = ~"TableColGroupFlow: ";
         txt.append(match self.box_ {

src/components/main/layout/table_row.rs

@@ -9,16 +9,14 @@ use layout::block::BlockFlow;
 use layout::block::WidthAndMarginsComputer;
 use layout::construct::FlowConstructor;
 use layout::context::LayoutContext;
-use layout::display_list_builder::{DisplayListBuilder, ExtraDisplayListData};
+use layout::display_list_builder::{DisplayListBuilder, DisplayListBuildingInfo};
 use layout::flow::{TableRowFlowClass, FlowClass, Flow, ImmutableFlowUtils};
 use layout::flow;
 use layout::table::InternalTable;
 use layout::model::{MaybeAuto, Specified, Auto};
 use layout::wrapper::ThreadSafeLayoutNode;
 
-use std::cell::RefCell;
-use geom::{Point2D, Rect, Size2D};
-use gfx::display_list::DisplayListCollection;
+use gfx::display_list::StackingContext;
 use servo_util::geometry::Au;
 use servo_util::geometry;
 
@@ -28,6 +26,12 @@ pub struct TableRowFlow {
 
     /// Column widths.
     col_widths: ~[Au],
+
+    /// Column min widths.
+    col_min_widths: ~[Au],
+
+    /// Column pref widths.
+    col_pref_widths: ~[Au],
 }
 
 impl TableRowFlow {
@@ -37,6 +41,8 @@ impl TableRowFlow {
         TableRowFlow {
             block_flow: BlockFlow::from_node_and_box(node, box_),
             col_widths: ~[],
+            col_min_widths: ~[],
+            col_pref_widths: ~[],
         }
     }
 
@@ -46,12 +52,16 @@ impl TableRowFlow {
         TableRowFlow {
             block_flow: BlockFlow::from_node(constructor, node),
             col_widths: ~[],
+            col_min_widths: ~[],
+            col_pref_widths: ~[],
         }
     }
 
     pub fn teardown(&mut self) {
         self.block_flow.teardown();
         self.col_widths = ~[];
+        self.col_min_widths = ~[];
+        self.col_pref_widths = ~[];
     }
 
     pub fn box_<'a>(&'a mut self) -> &'a Option<Box>{
@@ -66,19 +76,23 @@ impl TableRowFlow {
 
     /// Assign height for table-row flow.
     ///
+    /// TODO(pcwalton): This doesn't handle floats and positioned elements right.
+    ///
     /// inline(always) because this is only ever called by in-order or non-in-order top-level
     /// methods
     #[inline(always)]
-    fn assign_height_table_row_base(&mut self, ctx: &mut LayoutContext, inorder: bool) {
-        let (top_offset, bottom_offset, left_offset) = self.initialize_offsets();
+    fn assign_height_table_row_base(&mut self, layout_context: &mut LayoutContext, inorder: bool) {
+        let (top_offset, _, _) = self.initialize_offsets();
 
-        self.block_flow.handle_children_floats_if_necessary(ctx, inorder,
-                                                            left_offset, top_offset);
         let mut cur_y = top_offset;
 
         // Per CSS 2.1 § 17.5.3, find max_y = max( computed `height`, minimum height of all cells )
         let mut max_y = Au::new(0);
         for kid in self.block_flow.base.child_iter() {
+            if inorder {
+                kid.assign_height_inorder(layout_context)
+            }
+
             for child_box in kid.as_table_cell().box_().iter() {
                 // TODO: Percentage height
                 let child_specified_height = MaybeAuto::from_style(child_box.style().Box.get().height,
@@ -101,6 +115,8 @@ impl TableRowFlow {
         cur_y = cur_y + height;
 
         // Assign the height of own box
+        //
+        // FIXME(pcwalton): Take `cur_y` into account.
         for box_ in self.block_flow.box_.iter() {
             let mut position = box_.border_box.get();
             position.size.height = height;
@@ -118,24 +134,14 @@ impl TableRowFlow {
             let child_node = flow::mut_base(kid);
             child_node.position.size.height = height;
         }
-
-        self.block_flow.set_floats_out_if_inorder(inorder, height, cur_y,
-                                                  top_offset, bottom_offset, left_offset);
     }
 
-    pub fn build_display_list_table_row<E:ExtraDisplayListData>(
-                                        &mut self,
-                                        builder: &DisplayListBuilder,
-                                        container_block_size: &Size2D<Au>,
-                                        absolute_cb_abs_position: Point2D<Au>,
-                                        dirty: &Rect<Au>,
-                                        index: uint,
-                                        lists: &RefCell<DisplayListCollection<E>>)
-                                        -> uint {
+    pub fn build_display_list_table_row(&mut self,
+                                        stacking_context: &mut StackingContext,
+                                        builder: &mut DisplayListBuilder,
+                                        info: &DisplayListBuildingInfo) {
         debug!("build_display_list_table_row: same process as block flow");
-        self.block_flow.build_display_list_block(builder, container_block_size,
-                                                 absolute_cb_abs_position,
-                                                 dirty, index, lists)
+        self.block_flow.build_display_list_block(stacking_context, builder, info)
     }
 }
 
@@ -152,27 +158,51 @@ impl Flow for TableRowFlow {
         &mut self.block_flow
     }
 
+    fn col_widths<'a>(&'a mut self) -> &'a mut ~[Au] {
+        &mut self.col_widths
+    }
+
+    fn col_min_widths<'a>(&'a self) -> &'a ~[Au] {
+        &self.col_min_widths
+    }
+
+    fn col_pref_widths<'a>(&'a self) -> &'a ~[Au] {
+        &self.col_pref_widths
+    }
+
     /// Recursively (bottom-up) determines the context's preferred and minimum widths. When called
     /// on this context, all child contexts have had their min/pref widths set. This function must
     /// decide min/pref widths based on child context widths and dimensions of any boxes it is
     /// responsible for flowing.
     /// Min/pref widths set by this function are used in automatic table layout calculation.
-    /// Also, this function collects the specified column widths of children cells. Those are used
-    /// in fixed table layout calculation
-    fn bubble_widths(&mut self, ctx: &mut LayoutContext) {
+    /// The specified column widths of children cells are used in fixed table layout calculation.
+    fn bubble_widths(&mut self, _: &mut LayoutContext) {
+        let mut min_width = Au(0);
+        let mut pref_width = Au(0);
+        let mut num_floats = 0;
         /* find the specified widths from child table-cell contexts */
         for kid in self.block_flow.base.child_iter() {
             assert!(kid.is_table_cell());
 
+            // collect the specified column widths of cells. These are used in fixed table layout calculation.
             for child_box in kid.as_table_cell().box_().iter() {
                 let child_specified_width = MaybeAuto::from_style(child_box.style().Box.get().width,
                                                                   Au::new(0)).specified_or_zero();
                 self.col_widths.push(child_specified_width);
             }
-        }
 
-        // TODO: calculate min_width & pref_width for automatic table layout calculation
-        self.block_flow.bubble_widths(ctx);
+            // collect min_width & pref_width of children cells for automatic table layout calculation.
+            let child_base = flow::mut_base(kid);
+            self.col_min_widths.push(child_base.intrinsic_widths.minimum_width);
+            self.col_pref_widths.push(child_base.intrinsic_widths.preferred_width);
+            min_width = min_width + child_base.intrinsic_widths.minimum_width;
+            pref_width = pref_width + child_base.intrinsic_widths.preferred_width;
+            num_floats = num_floats + child_base.num_floats;
+        }
+        self.block_flow.base.num_floats = num_floats;
+        self.block_flow.base.intrinsic_widths.minimum_width = min_width;
+        self.block_flow.base.intrinsic_widths.preferred_width = geometry::max(min_width,
+                                                                              pref_width);
     }
 
     /// Recursively (top-down) determines the actual width of child contexts and boxes. When called
@@ -205,12 +235,6 @@ impl Flow for TableRowFlow {
         self.assign_height_table_row_base(ctx, false);
     }
 
-    /// TableRowBox and their parents(TableBox) do not have margins.
-    /// Therefore, margins to be collapsed do not exist.
-    fn collapse_margins(&mut self, _: bool, _: &mut bool, _: &mut Au,
-                        _: &mut Au, _: &mut Au, _: &mut Au) {
-    }
-
     fn debug_str(&self) -> ~str {
         let txt = ~"TableRowFlow: ";
         txt.append(match self.block_flow.box_ {

src/components/main/layout/table_rowgroup.rs

@@ -9,16 +9,15 @@ use layout::block::BlockFlow;
 use layout::block::WidthAndMarginsComputer;
 use layout::construct::FlowConstructor;
 use layout::context::LayoutContext;
-use layout::display_list_builder::{DisplayListBuilder, ExtraDisplayListData};
+use layout::display_list_builder::{DisplayListBuilder, DisplayListBuildingInfo};
 use layout::flow::{TableRowGroupFlowClass, FlowClass, Flow, ImmutableFlowUtils};
 use layout::flow;
-use layout::table::InternalTable;
+use layout::table::{InternalTable, TableFlow};
 use layout::wrapper::ThreadSafeLayoutNode;
 
-use std::cell::RefCell;
-use geom::{Point2D, Rect, Size2D};
-use gfx::display_list::DisplayListCollection;
+use gfx::display_list::StackingContext;
 use servo_util::geometry::Au;
+use servo_util::geometry;
 
 /// A table formatting context.
 pub struct TableRowGroupFlow {
@@ -26,6 +25,12 @@ pub struct TableRowGroupFlow {
 
     /// Column widths
     col_widths: ~[Au],
+
+    /// Column min widths.
+    col_min_widths: ~[Au],
+
+    /// Column pref widths.
+    col_pref_widths: ~[Au],
 }
 
 impl TableRowGroupFlow {
@@ -35,6 +40,8 @@ impl TableRowGroupFlow {
         TableRowGroupFlow {
             block_flow: BlockFlow::from_node_and_box(node, box_),
             col_widths: ~[],
+            col_min_widths: ~[],
+            col_pref_widths: ~[],
         }
     }
 
@@ -44,12 +51,16 @@ impl TableRowGroupFlow {
         TableRowGroupFlow {
             block_flow: BlockFlow::from_node(constructor, node),
             col_widths: ~[],
+            col_min_widths: ~[],
+            col_pref_widths: ~[],
         }
     }
 
     pub fn teardown(&mut self) {
         self.block_flow.teardown();
         self.col_widths = ~[];
+        self.col_min_widths = ~[];
+        self.col_pref_widths = ~[];
     }
 
     pub fn box_<'a>(&'a mut self) -> &'a Option<Box>{
@@ -64,14 +75,14 @@ impl TableRowGroupFlow {
 
     /// Assign height for table-rowgroup flow.
     ///
+    /// FIXME(pcwalton): This doesn't handle floats right.
+    ///
     /// inline(always) because this is only ever called by in-order or non-in-order top-level
     /// methods
     #[inline(always)]
-    fn assign_height_table_rowgroup_base(&mut self, ctx: &mut LayoutContext, inorder: bool) {
-        let (top_offset, bottom_offset, left_offset) = self.initialize_offsets();
+    fn assign_height_table_rowgroup_base(&mut self, _: &mut LayoutContext, _: bool) {
+        let (top_offset, _, _) = self.initialize_offsets();
 
-        self.block_flow.handle_children_floats_if_necessary(ctx, inorder,
-                                                            left_offset, top_offset);
         let mut cur_y = top_offset;
 
         for kid in self.block_flow.base.child_iter() {
@@ -88,24 +99,14 @@ impl TableRowGroupFlow {
             box_.border_box.set(position);
         }
         self.block_flow.base.position.size.height = height;
-
-        self.block_flow.set_floats_out_if_inorder(inorder, height, cur_y,
-                                                  top_offset, bottom_offset, left_offset);
     }
 
-    pub fn build_display_list_table_rowgroup<E:ExtraDisplayListData>(
-                                            &mut self,
-                                            builder: &DisplayListBuilder,
-                                            container_block_size: &Size2D<Au>,
-                                            absolute_cb_abs_position: Point2D<Au>,
-                                            dirty: &Rect<Au>,
-                                            index: uint,
-                                            lists: &RefCell<DisplayListCollection<E>>)
-                                            -> uint {
+    pub fn build_display_list_table_rowgroup(&mut self,
+                                             stacking_context: &mut StackingContext,
+                                             builder: &mut DisplayListBuilder,
+                                             info: &DisplayListBuildingInfo) {
         debug!("build_display_list_table_rowgroup: same process as block flow");
-        self.block_flow.build_display_list_block(builder, container_block_size,
-                                                 absolute_cb_abs_position,
-                                                 dirty, index, lists)
+        self.block_flow.build_display_list_block(stacking_context, builder, info)
     }
 }
 
@@ -122,6 +123,18 @@ impl Flow for TableRowGroupFlow {
         &mut self.block_flow
     }
 
+    fn col_widths<'a>(&'a mut self) -> &'a mut ~[Au] {
+        &mut self.col_widths
+    }
+
+    fn col_min_widths<'a>(&'a self) -> &'a ~[Au] {
+        &self.col_min_widths
+    }
+
+    fn col_pref_widths<'a>(&'a self) -> &'a ~[Au] {
+        &self.col_pref_widths
+    }
+
     /// Recursively (bottom-up) determines the context's preferred and minimum widths. When called
     /// on this context, all child contexts have had their min/pref widths set. This function must
     /// decide min/pref widths based on child context widths and dimensions of any boxes it is
@@ -129,24 +142,48 @@ impl Flow for TableRowGroupFlow {
     /// Min/pref widths set by this function are used in automatic table layout calculation.
     /// Also, this function finds the specified column widths from the first row.
     /// Those are used in fixed table layout calculation
-    fn bubble_widths(&mut self, ctx: &mut LayoutContext) {
-        /* find the specified column widths from the first table-row.
-           update the number of column widths from other table-rows. */
+    fn bubble_widths(&mut self, _: &mut LayoutContext) {
+        let mut min_width = Au(0);
+        let mut pref_width = Au(0);
+        let mut num_floats = 0;
+
         for kid in self.block_flow.base.child_iter() {
             assert!(kid.is_table_row());
-            if self.col_widths.is_empty() {
-                self.col_widths = kid.as_table_row().col_widths.clone();
+
+            // calculate min_width & pref_width for automatic table layout calculation
+            // 'self.col_min_widths' collects the maximum value of cells' min-widths for each column.
+            // 'self.col_pref_widths' collects the maximum value of cells' pref-widths for each column.
+            if self.col_widths.is_empty() { // First Row
+                assert!(self.col_min_widths.is_empty() && self.col_pref_widths.is_empty());
+                // 'self.col_widths' collects the specified column widths from the first table-row for fixed table layout calculation.
+                self.col_widths = kid.col_widths().clone();
+                self.col_min_widths = kid.col_min_widths().clone();
+                self.col_pref_widths = kid.col_pref_widths().clone();
             } else {
+                min_width = TableFlow::update_col_widths(&mut self.col_min_widths, kid.col_min_widths());
+                pref_width = TableFlow::update_col_widths(&mut self.col_pref_widths, kid.col_pref_widths());
+
+                // update the number of column widths from table-rows.
                 let num_cols = self.col_widths.len();
-                let num_child_cols = kid.as_table_row().col_widths.len();
-                for _ in range(num_cols, num_child_cols) {
+                let num_child_cols = kid.col_min_widths().len();
+                for i in range(num_cols, num_child_cols) {
                     self.col_widths.push(Au::new(0));
+                    let new_kid_min = kid.col_min_widths()[i];
+                    self.col_min_widths.push(kid.col_min_widths()[i]);
+                    let new_kid_pref = kid.col_pref_widths()[i];
+                    self.col_pref_widths.push(kid.col_pref_widths()[i]);
+                    min_width = min_width + new_kid_min;
+                    pref_width = pref_width + new_kid_pref;
                 }
             }
+            let child_base = flow::mut_base(kid);
+            num_floats = num_floats + child_base.num_floats;
         }
 
-        // TODO: calculate min_width & pref_width for automatic table layout calculation
-        self.block_flow.bubble_widths(ctx);
+        self.block_flow.base.num_floats = num_floats;
+        self.block_flow.base.intrinsic_widths.minimum_width = min_width;
+        self.block_flow.base.intrinsic_widths.preferred_width = geometry::max(min_width,
+                                                                              pref_width);
     }
 
     /// Recursively (top-down) determines the actual width of child contexts and boxes. When called
@@ -180,12 +217,6 @@ impl Flow for TableRowGroupFlow {
         self.assign_height_table_rowgroup_base(ctx, false);
     }
 
-    /// TableRowBox and their parents(TableBox) do not have margins.
-    /// Therefore, margins to be collapsed do not exist.
-    fn collapse_margins(&mut self, _: bool, _: &mut bool, _: &mut Au,
-                        _: &mut Au, _: &mut Au, _: &mut Au) {
-    }
-
     fn debug_str(&self) -> ~str {
         let txt = ~"TableRowGroupFlow: ";
         txt.append(match self.block_flow.box_ {

src/components/main/layout/table_wrapper.rs

@@ -5,23 +5,20 @@
 //! CSS table formatting contexts.
 
 use layout::box_::Box;
-use layout::block::BlockFlow;
-use layout::block::{WidthAndMarginsComputer, WidthConstraintInput, WidthConstraintSolution};
+use layout::block::{BlockFlow, MarginsMayNotCollapse, WidthAndMarginsComputer};
+use layout::block::{WidthConstraintInput, WidthConstraintSolution};
 use layout::construct::FlowConstructor;
 use layout::context::LayoutContext;
-use layout::display_list_builder::{DisplayListBuilder, ExtraDisplayListData};
-use layout::floats::{FloatKind};
+use layout::display_list_builder::{DisplayListBuilder, DisplayListBuildingInfo};
+use layout::floats::FloatKind;
 use layout::flow::{TableWrapperFlowClass, FlowClass, Flow, ImmutableFlowUtils};
-use layout::flow;
-use layout::model::{MaybeAuto, Specified, Auto, specified};
+use layout::model::{Specified, Auto, specified};
 use layout::wrapper::ThreadSafeLayoutNode;
 
-use std::cell::RefCell;
-use style::computed_values::table_layout;
-use geom::{Point2D, Rect, Size2D};
-use gfx::display_list::DisplayListCollection;
+use gfx::display_list::StackingContext;
 use servo_util::geometry::Au;
 use servo_util::geometry;
+use style::computed_values::table_layout;
 
 pub enum TableLayout {
     FixedLayout,
@@ -103,77 +100,22 @@ impl TableWrapperFlow {
 
     /// Assign height for table-wrapper flow.
     /// `Assign height` of table-wrapper flow follows a similar process to that of block flow.
-    /// However, table-wrapper flow doesn't consider collapsing margins for flow's children
-    /// and calculating padding/border.
     ///
     /// inline(always) because this is only ever called by in-order or non-in-order top-level
     /// methods
     #[inline(always)]
-    fn assign_height_table_wrapper_base(&mut self, ctx: &mut LayoutContext, inorder: bool) {
-
-        // Note: Ignoring clearance for absolute flows as of now.
-        let ignore_clear = self.is_absolutely_positioned();
-        let (clearance, top_offset, bottom_offset, left_offset) = self.block_flow.initialize_offsets(ignore_clear);
-
-        self.block_flow.handle_children_floats_if_necessary(ctx, inorder,
-                                                            left_offset, top_offset);
-
-        // Table wrapper flow has margin but is not collapsed with kids(table caption and table).
-        let (margin_top, margin_bottom, _, _) = self.block_flow.precompute_margin();
-
-        let mut cur_y = top_offset;
-
-        for kid in self.block_flow.base.child_iter() {
-            let child_node = flow::mut_base(kid);
-            child_node.position.origin.y = cur_y;
-            cur_y = cur_y + child_node.position.size.height;
-        }
-
-        // top_offset: top margin-edge of the topmost child.
-        // hence, height = content height
-        let mut height = cur_y - top_offset;
-
-        // For an absolutely positioned element, store the content height and stop the function.
-        if self.block_flow.store_content_height_if_absolutely_positioned(height) {
-            return;
-        }
-
-        for box_ in self.block_flow.box_.iter() {
-            let style = box_.style();
-
-            // At this point, `height` is the height of the containing block, so passing `height`
-            // as the second argument here effectively makes percentages relative to the containing
-            // block per CSS 2.1 § 10.5.
-            height = match MaybeAuto::from_style(style.Box.get().height, height) {
-                Auto => height,
-                Specified(value) => geometry::max(value, height)
-            };
-        }
-
-        self.block_flow.compute_height_position(&mut height,
-                                                Au(0),
-                                                margin_top,
-                                                margin_bottom,
-                                                clearance);
-
-        self.block_flow.set_floats_out_if_inorder(inorder, height, cur_y,
-                                                  top_offset, bottom_offset, left_offset);
-        self.block_flow.assign_height_absolute_flows(ctx);
+    fn assign_height_table_wrapper_base(&mut self,
+                                        layout_context: &mut LayoutContext,
+                                        inorder: bool) {
+        self.block_flow.assign_height_block_base(layout_context, inorder, MarginsMayNotCollapse);
     }
 
-    pub fn build_display_list_table_wrapper<E:ExtraDisplayListData>(
-                                            &mut self,
-                                            builder: &DisplayListBuilder,
-                                            container_block_size: &Size2D<Au>,
-                                            absolute_cb_abs_position: Point2D<Au>,
-                                            dirty: &Rect<Au>,
-                                            index: uint,
-                                            lists: &RefCell<DisplayListCollection<E>>)
-                                            -> uint {
+    pub fn build_display_list_table_wrapper(&mut self,
+                                            stacking_context: &mut StackingContext,
+                                            builder: &mut DisplayListBuilder,
+                                            info: &DisplayListBuildingInfo) {
         debug!("build_display_list_table_wrapper: same process as block flow");
-        self.block_flow.build_display_list_block(builder, container_block_size,
-                                                 absolute_cb_abs_position,
-                                                 dirty, index, lists)
+        self.block_flow.build_display_list_block(stacking_context, builder, info);
     }
 }
 
@@ -197,7 +139,7 @@ impl Flow for TableWrapperFlow {
     any boxes it is responsible for flowing.  */
 
     fn bubble_widths(&mut self, ctx: &mut LayoutContext) {
-        /* find max width from child block contexts */
+        // get column widths info from table flow
         for kid in self.block_flow.base.child_iter() {
             assert!(kid.is_table_caption() || kid.is_table());
 
@@ -227,8 +169,6 @@ impl Flow for TableWrapperFlow {
         let mut left_content_edge = Au::new(0);
         let mut content_width = containing_block_width;
 
-        self.block_flow.set_containing_width_if_float(containing_block_width);
-
         let width_computer = TableWrapper;
         width_computer.compute_used_width_table_wrapper(self, ctx, containing_block_width);
 
@@ -243,7 +183,12 @@ impl Flow for TableWrapperFlow {
             _ => {}
         }
 
-        self.block_flow.propagate_assigned_width_to_children(left_content_edge, content_width, None);
+        // In case of fixed layout, column widths are calculated in table flow.
+        let assigned_col_widths = match self.table_layout {
+            FixedLayout => None,
+            AutoLayout => Some(self.col_widths.clone())
+        };
+        self.block_flow.propagate_assigned_width_to_children(left_content_edge, content_width, assigned_col_widths);
     }
 
     /// This is called on kid flows by a parent.
@@ -270,26 +215,6 @@ impl Flow for TableWrapperFlow {
         }
     }
 
-    // CSS Section 8.3.1 - Collapsing Margins
-    // `self`: the Flow whose margins we want to collapse.
-    // `collapsing`: value to be set by this function. This tells us how much
-    // of the top margin has collapsed with a previous margin.
-    // `collapsible`: Potential collapsible margin at the bottom of this flow's box.
-    fn collapse_margins(&mut self,
-                        top_margin_collapsible: bool,
-                        first_in_flow: &mut bool,
-                        margin_top: &mut Au,
-                        top_offset: &mut Au,
-                        collapsing: &mut Au,
-                        collapsible: &mut Au) {
-        self.block_flow.collapse_margins(top_margin_collapsible,
-                                         first_in_flow,
-                                         margin_top,
-                                         top_offset,
-                                         collapsing,
-                                         collapsible);
-    }
-
     fn debug_str(&self) -> ~str {
         let txt = if self.is_float() {
             ~"TableWrapperFlow(Float): "
@@ -327,10 +252,12 @@ impl TableWrapper {
         let mut input = self.compute_width_constraint_inputs(&mut table_wrapper.block_flow,
                                                              parent_flow_width,
                                                              ctx);
-        match table_wrapper.table_layout {
+        let computed_width = match table_wrapper.table_layout {
             FixedLayout => {
                 let fixed_cells_width = table_wrapper.col_widths.iter().fold(Au(0),
                                                                              |sum, width| sum.add(width));
+
+                let mut computed_width = input.computed_width.specified_or_zero();
                 for box_ in table_wrapper.block_flow.box_.iter() {
                     let style = box_.style();
 
@@ -344,15 +271,72 @@ impl TableWrapper {
                     let border_left = style.Border.get().border_left_width;
                     let border_right = style.Border.get().border_right_width;
                     let padding_and_borders = padding_left + padding_right + border_left + border_right;
-                    let mut computed_width = input.computed_width.specified_or_zero();
                     // Compare border-edge widths. Because fixed_cells_width indicates content-width,
                     // padding and border values are added to fixed_cells_width.
                     computed_width = geometry::max(fixed_cells_width + padding_and_borders, computed_width);
-                    input.computed_width = Specified(computed_width);
                 }
+                computed_width
             },
-            _ => {}
-        }
+            AutoLayout => {
+                // Automatic table layout is calculated according to CSS 2.1 § 17.5.2.2.
+                let mut cap_min = Au(0);
+                let mut cols_min = Au(0);
+                let mut cols_max = Au(0);
+                let mut col_min_widths = &~[];
+                let mut col_pref_widths = &~[];
+                for kid in table_wrapper.block_flow.base.child_iter() {
+                    if kid.is_table_caption() {
+                        cap_min = kid.as_block().base.intrinsic_widths.minimum_width;
+                    } else {
+                        assert!(kid.is_table());
+                        cols_min = kid.as_block().base.intrinsic_widths.minimum_width;
+                        cols_max = kid.as_block().base.intrinsic_widths.preferred_width;
+                        col_min_widths = kid.col_min_widths();
+                        col_pref_widths = kid.col_pref_widths();
+                    }
+                }
+                // 'extra_width': difference between the calculated table width and minimum width
+                // required by all columns. It will be distributed over the columns.
+                let (width, extra_width) = match input.computed_width {
+                    Auto => {
+                        if input.available_width > geometry::max(cols_max, cap_min) {
+                            if cols_max > cap_min {
+                                table_wrapper.col_widths = col_pref_widths.clone();
+                                (cols_max, Au(0))
+                            } else {
+                                (cap_min, cap_min - cols_min)
+                            }
+                        } else {
+                            let max = if cols_min >= input.available_width && cols_min >= cap_min {
+                                table_wrapper.col_widths = col_min_widths.clone();
+                                cols_min
+                            } else {
+                                geometry::max(input.available_width, cap_min)
+                            };
+                            (max, max - cols_min)
+                        }
+                    },
+                    Specified(width) => {
+                        let max = if cols_min >= width && cols_min >= cap_min {
+                            table_wrapper.col_widths = col_min_widths.clone();
+                            cols_min
+                        } else {
+                            geometry::max(width, cap_min)
+                        };
+                        (max, max - cols_min)
+                    }
+                };
+                // The extra width is distributed over the columns
+                if extra_width > Au(0) {
+                    let cell_len = table_wrapper.col_widths.len() as f64;
+                    table_wrapper.col_widths = col_min_widths.map(|width| {
+                        width + extra_width.scale_by(1.0 / cell_len)
+                    });
+                }
+                width
+            }
+        };
+        input.computed_width = Specified(computed_width);
         input
     }
 }

src/components/main/layout/util.rs

@@ -7,6 +7,7 @@ use layout::construct::{ConstructionResult, NoConstructionResult};
 use layout::parallel::DomParallelInfo;
 use layout::wrapper::{LayoutNode, TLayoutNode, ThreadSafeLayoutNode};
 
+use gfx::display_list::OpaqueNode;
 use script::dom::bindings::js::JS;
 use script::dom::bindings::utils::Reflectable;
 use script::dom::node::Node;
@@ -146,6 +147,10 @@ pub struct PrivateLayoutData {
     /// `ConstructionItem`. See comments in `construct.rs` for more details.
     flow_construction_result: ConstructionResult,
 
+    before_flow_construction_result: ConstructionResult,
+
+    after_flow_construction_result: ConstructionResult,
+
     /// Information needed during parallel traversals.
     parallel: DomParallelInfo,
 }
@@ -159,6 +164,8 @@ impl PrivateLayoutData {
             after_style: None,
             restyle_damage: None,
             flow_construction_result: NoConstructionResult,
+            before_flow_construction_result: NoConstructionResult,
+            after_flow_construction_result: NoConstructionResult,
             parallel: DomParallelInfo::new(),
         }
     }
@@ -200,40 +207,45 @@ impl<'ln> LayoutDataAccess for LayoutNode<'ln> {
     }
 }
 
-/// An opaque handle to a node. The only safe operation that can be performed on this node is to
-/// compare it to another opaque handle or to another node.
-///
-/// Because the script task's GC does not trace layout, node data cannot be safely stored in layout
-/// data structures. Also, layout code tends to be faster when the DOM is not being accessed, for
-/// locality reasons. Using `OpaqueNode` enforces this invariant.
-#[deriving(Clone, Eq)]
-pub struct OpaqueNode(uintptr_t);
-
-impl OpaqueNode {
+pub trait OpaqueNodeMethods {
     /// Converts a DOM node (layout view) to an `OpaqueNode`.
-    pub fn from_layout_node(node: &LayoutNode) -> OpaqueNode {
+    fn from_layout_node(node: &LayoutNode) -> Self;
+
+    /// Converts a thread-safe DOM node (layout view) to an `OpaqueNode`.
+    fn from_thread_safe_layout_node(node: &ThreadSafeLayoutNode) -> Self;
+
+    /// Converts a DOM node (script view) to an `OpaqueNode`.
+    fn from_script_node(node: TrustedNodeAddress) -> Self;
+
+    /// Converts a DOM node to an `OpaqueNode'.
+    fn from_jsmanaged(node: &JS<Node>) -> Self;
+
+    /// Converts this node to an `UntrustedNodeAddress`. An `UntrustedNodeAddress` is just the type
+    /// of node that script expects to receive in a hit test.
+    fn to_untrusted_node_address(&self) -> UntrustedNodeAddress;
+}
+
+impl OpaqueNodeMethods for OpaqueNode {
+    fn from_layout_node(node: &LayoutNode) -> OpaqueNode {
         unsafe {
-            OpaqueNode::from_jsmanaged(node.get_jsmanaged())
+            OpaqueNodeMethods::from_jsmanaged(node.get_jsmanaged())
         }
     }
 
-    /// Converts a thread-safe DOM node (layout view) to an `OpaqueNode`.
-    pub fn from_thread_safe_layout_node(node: &ThreadSafeLayoutNode) -> OpaqueNode {
+    fn from_thread_safe_layout_node(node: &ThreadSafeLayoutNode) -> OpaqueNode {
         unsafe {
             let abstract_node = node.get_jsmanaged();
-            let ptr: uintptr_t = cast::transmute(abstract_node.reflector().get_jsobject());
+            let ptr: uintptr_t = abstract_node.reflector().get_jsobject() as uint;
             OpaqueNode(ptr)
         }
     }
 
-    /// Converts a DOM node (script view) to an `OpaqueNode`.
-    pub fn from_script_node(node: TrustedNodeAddress) -> OpaqueNode {
+    fn from_script_node(node: TrustedNodeAddress) -> OpaqueNode {
         unsafe {
-            OpaqueNode::from_jsmanaged(&JS::from_trusted_node_address(node))
+            OpaqueNodeMethods::from_jsmanaged(&JS::from_trusted_node_address(node))
         }
     }
 
-    /// Converts a DOM node to an `OpaqueNode'.
     fn from_jsmanaged(node: &JS<Node>) -> OpaqueNode {
         unsafe {
             let ptr: uintptr_t = cast::transmute(node.reflector().get_jsobject());
@@ -241,9 +253,7 @@ impl OpaqueNode {
         }
     }
 
-    /// Converts this node to an `UntrustedNodeAddress`. An `UntrustedNodeAddress` is just the type
-    /// of node that script expects to receive in a hit test.
-    pub fn to_untrusted_node_address(&self) -> UntrustedNodeAddress {
+    fn to_untrusted_node_address(&self) -> UntrustedNodeAddress {
         unsafe {
             let OpaqueNode(addr) = *self;
             let addr: UntrustedNodeAddress = cast::transmute(addr);
@@ -251,11 +261,5 @@ impl OpaqueNode {
         }
     }
 
-    /// Returns the address of this node, for debugging purposes.
-    pub fn id(&self) -> uintptr_t {
-        unsafe {
-            cast::transmute_copy(self)
-        }
-    }
 }
 

src/components/main/layout/wrapper.rs

@@ -50,7 +50,7 @@ use std::cast;
 use std::cell::{Ref, RefMut};
 use style::{PropertyDeclarationBlock, TElement, TNode, AttrSelector, SpecificNamespace};
 use style::{AnyNamespace};
-
+use style::computed_values::{content, display};
 use layout::util::LayoutDataWrapper;
 
 /// Allows some convenience methods on generic layout nodes.
@@ -58,8 +58,9 @@ pub trait TLayoutNode {
     /// Creates a new layout node with the same lifetime as this layout node.
     unsafe fn new_with_this_lifetime(&self, node: &JS<Node>) -> Self;
 
-    /// Returns the type ID of this node. Fails if this node is borrowed mutably.
-    fn type_id(&self) -> NodeTypeId;
+    /// Returns the type ID of this node. Fails if this node is borrowed mutably. Returns `None`
+    /// if this is a pseudo-element; otherwise, returns `Some`.
+    fn type_id(&self) -> Option<NodeTypeId>;
 
     /// Returns the interior of this node as a `JS`. This is highly unsafe for layout to
     /// call and as such is marked `unsafe`.
@@ -73,14 +74,14 @@ pub trait TLayoutNode {
 
     fn node_is_element(&self) -> bool {
         match self.type_id() {
-            ElementNodeTypeId(..) => true,
+            Some(ElementNodeTypeId(..)) => true,
             _ => false
         }
     }
 
     fn node_is_document(&self) -> bool {
         match self.type_id() {
-            DocumentNodeTypeId(..) => true,
+            Some(DocumentNodeTypeId(..)) => true,
             _ => false
         }
     }
@@ -114,22 +115,10 @@ pub trait TLayoutNode {
     /// If this is a text node, copies out the text. If this is not a text node, fails.
     ///
     /// FIXME(pcwalton): Don't copy text. Atomically reference count instead.
-    fn text(&self) -> ~str {
-        unsafe {
-            if !self.get().is_text() {
-                fail!("not text!")
-            }
-            let text: JS<Text> = self.get_jsmanaged().transmute_copy();
-            (*text.unsafe_get()).characterdata.data.to_str()
-        }
-    }
+    fn text(&self) -> ~str;
 
     /// Returns the first child of this node.
-    fn first_child(&self) -> Option<Self> {
-        unsafe {
-            self.get().first_child_ref().map(|node| self.new_with_this_lifetime(node))
-        }
-    }
+    fn first_child(&self) -> Option<Self>;
 
     /// Dumps this node tree, for debugging.
     fn dump(&self) {
@@ -144,7 +133,7 @@ pub struct LayoutNode<'a> {
     priv node: JS<Node>,
 
     /// Being chained to a value prevents `LayoutNode`s from escaping.
-    priv chain: &'a (),
+    chain: &'a (),
 }
 
 impl<'ln> Clone for LayoutNode<'ln> {
@@ -172,12 +161,30 @@ impl<'ln> TLayoutNode for LayoutNode<'ln> {
             chain: self.chain,
         }
     }
-    fn type_id(&self) -> NodeTypeId {
-        self.node.type_id()
+
+    fn type_id(&self) -> Option<NodeTypeId> {
+        Some(self.node.type_id())
     }
+
     unsafe fn get_jsmanaged<'a>(&'a self) -> &'a JS<Node> {
         &self.node
     }
+
+    fn first_child(&self) -> Option<LayoutNode<'ln>> {
+        unsafe {
+            self.get().first_child_ref().map(|node| self.new_with_this_lifetime(node))
+        }
+    }
+
+    fn text(&self) -> ~str {
+        unsafe {
+            if !self.get().is_text() {
+                fail!("not text!")
+            }
+            let text: JS<Text> = self.get_jsmanaged().transmute_copy();
+            (*text.unsafe_get()).characterdata.data.to_str()
+        }
+    }
 }
 
 impl<'ln> LayoutNode<'ln> {
@@ -205,6 +212,10 @@ impl<'ln> LayoutNode<'ln> {
             current_node: self.first_child(),
         }
     }
+
+   pub unsafe fn get_jsmanaged<'a>(&'a self) -> &'a JS<Node> {
+       &self.node
+   }
 }
 
 impl<'ln> TNode<LayoutElement<'ln>> for LayoutNode<'ln> {
@@ -371,29 +382,107 @@ impl<'le> TElement for LayoutElement<'le> {
     }
 }
 
+fn get_content(content_list: &content::T) -> ~str {
+    match *content_list {
+        content::Content(ref value) => {
+            let iter = &mut value.clone().move_iter().peekable();
+            match iter.next() {
+                Some(content::StringContent(content)) => content,
+                _ => ~"",
+            }
+        }
+        _ => ~"",
+    }
+}
+
+#[deriving(Eq, Clone)]
+pub enum ElementType {
+    Normal,
+    Before,
+    After,
+    BeforeBlock,
+    AfterBlock,
+}
+
 /// A thread-safe version of `LayoutNode`, used during flow construction. This type of layout
 /// node does not allow any parents or siblings of nodes to be accessed, to avoid races.
 pub struct ThreadSafeLayoutNode<'ln> {
     /// The wrapped node.
-    priv node: JS<Node>,
+    priv node: LayoutNode<'ln>,
 
-    /// Being chained to a value prevents `ThreadSafeLayoutNode`s from escaping.
-    priv chain: &'ln (),
+    priv pseudo: ElementType,
 }
 
 impl<'ln> TLayoutNode for ThreadSafeLayoutNode<'ln> {
     /// Creates a new layout node with the same lifetime as this layout node.
     unsafe fn new_with_this_lifetime(&self, node: &JS<Node>) -> ThreadSafeLayoutNode<'ln> {
         ThreadSafeLayoutNode {
-            node: node.transmute_copy(),
-            chain: self.chain,
+            node: LayoutNode {
+                node: node.transmute_copy(),
+                chain: self.node.chain,
+            },
+            pseudo: Normal,
         }
     }
-    fn type_id(&self) -> NodeTypeId {
+
+    /// Returns `None` if this is a pseudo-element.
+    fn type_id(&self) -> Option<NodeTypeId> {
+        if self.pseudo == Before || self.pseudo == After {
+            return None
+        }
+
         self.node.type_id()
     }
+
     unsafe fn get_jsmanaged<'a>(&'a self) -> &'a JS<Node> {
-        &self.node
+        self.node.get_jsmanaged()
+    }
+
+    unsafe fn get<'a>(&'a self) -> &'a Node { // this change.
+        cast::transmute::<*mut Node,&'a Node>(self.get_jsmanaged().unsafe_get())
+    }
+
+    fn first_child(&self) -> Option<ThreadSafeLayoutNode<'ln>> {
+        if self.pseudo == Before || self.pseudo == After {
+            return None
+        }
+
+        if self.has_before_pseudo() {
+            if self.is_block(Before) && self.pseudo == Normal {
+                let pseudo_before_node = ThreadSafeLayoutNode::new_with_pseudo_without_self(&self.node, BeforeBlock);
+                return Some(pseudo_before_node)
+            } else if self.pseudo == Normal || self.pseudo == BeforeBlock {
+                let pseudo_before_node = ThreadSafeLayoutNode::new_with_pseudo_without_self(&self.node, Before);
+                return Some(pseudo_before_node)
+            }
+        }
+
+        unsafe {
+            self.get().first_child_ref().map(|node| self.new_with_this_lifetime(node))
+        }
+    }
+
+    fn text(&self) -> ~str {
+        if self.pseudo == Before || self.pseudo == After {
+            let layout_data_ref = self.borrow_layout_data();
+            let node_layout_data_wrapper = layout_data_ref.get().get_ref();
+
+            if self.pseudo == Before {
+                let before_style = node_layout_data_wrapper.data.before_style.get_ref();
+                return get_content(&before_style.get().Box.get().content)
+            } else {
+                let after_style = node_layout_data_wrapper.data.after_style.get_ref();
+                return get_content(&after_style.get().Box.get().content)
+            }
+        }
+
+        unsafe {
+            if !self.get().is_text() {
+                fail!("not text!")
+            }
+            let text: JS<Text> = self.get_jsmanaged().transmute_copy();
+            (*text.unsafe_get()).characterdata.data.to_str()
+        }
     }
 }
 
@@ -401,7 +490,7 @@ impl<'ln> Clone for ThreadSafeLayoutNode<'ln> {
     fn clone(&self) -> ThreadSafeLayoutNode<'ln> {
         ThreadSafeLayoutNode {
             node: self.node.clone(),
-            chain: self.chain,
+            pseudo: self.pseudo,
         }
     }
 }
@@ -410,13 +499,33 @@ impl<'ln> ThreadSafeLayoutNode<'ln> {
     /// Creates a new `ThreadSafeLayoutNode` from the given `LayoutNode`.
     pub fn new<'a>(node: &LayoutNode<'a>) -> ThreadSafeLayoutNode<'a> {
         ThreadSafeLayoutNode {
-            node: node.node.clone(),
-            chain: node.chain,
+            node: node.clone(),
+            pseudo: Normal,
+        }
+    }
+
+    pub fn new_with_pseudo_without_self<'a>(node: &LayoutNode<'a>, element_type: ElementType) -> ThreadSafeLayoutNode<'a> {
+         ThreadSafeLayoutNode {
+             node: node.clone(),
+             pseudo: element_type,
+         }
+    }
+
+
+    /// Creates a new `ThreadSafeLayoutNode` from the given `LayoutNode`.
+    pub fn new_with_pseudo<'a>(&'a self, element_type: ElementType) -> ThreadSafeLayoutNode<'a> {
+        ThreadSafeLayoutNode {
+            node: self.node.clone(),
+            pseudo: element_type,
         }
     }
 
     /// Returns the next sibling of this node. Unsafe and private because this can lead to races.
     unsafe fn next_sibling(&self) -> Option<ThreadSafeLayoutNode<'ln>> {
+        if self.pseudo == Before || self.pseudo == BeforeBlock {
+            return self.get().first_child_ref().map(|node| self.new_with_this_lifetime(node))
+        }
+
         self.node.get().next_sibling_ref().map(|node| self.new_with_this_lifetime(node))
     }
 
@@ -424,6 +533,7 @@ impl<'ln> ThreadSafeLayoutNode<'ln> {
     pub fn children(&self) -> ThreadSafeLayoutNodeChildrenIterator<'ln> {
         ThreadSafeLayoutNodeChildrenIterator {
             current_node: self.first_child(),
+            parent_node: Some(ThreadSafeLayoutNode::new_with_pseudo_without_self(&self.node, self.pseudo)),
         }
     }
 
@@ -431,7 +541,7 @@ impl<'ln> ThreadSafeLayoutNode<'ln> {
     #[inline]
     pub fn as_element(&self) -> ThreadSafeLayoutElement {
         unsafe {
-            let elem: JS<Element> = self.node.transmute_copy();
+            let elem: JS<Element> = self.node.get_jsmanaged().transmute_copy();
             let element = elem.unsafe_get();
             // FIXME(pcwalton): Workaround until Rust gets multiple lifetime parameters on
             // implementations.
@@ -441,6 +551,44 @@ impl<'ln> ThreadSafeLayoutNode<'ln> {
         }
     }
 
+    pub fn get_element_type(&self) ->  ElementType {
+        self.pseudo
+    }
+
+    pub fn is_block(&self, kind: ElementType) -> bool {
+        let mut layout_data_ref = self.mutate_layout_data();
+        let node_layout_data_wrapper = layout_data_ref.get().get_mut_ref();
+
+        let display = match kind {
+            Before | BeforeBlock => {
+                let before_style = node_layout_data_wrapper.data.before_style.get_ref();
+                before_style.get().Box.get().display
+            }
+            After | AfterBlock => {
+                let after_style = node_layout_data_wrapper.data.after_style.get_ref();
+                after_style.get().Box.get().display
+            }
+            Normal => {
+                let after_style = node_layout_data_wrapper.data.style.get_ref();
+                after_style.get().Box.get().display
+            }
+        };
+
+        display == display::block
+    }
+
+    pub fn has_before_pseudo(&self) -> bool {
+        let layout_data_wrapper = self.borrow_layout_data();
+        let layout_data_wrapper_ref = layout_data_wrapper.get().get_ref();
+        layout_data_wrapper_ref.data.before_style.is_some()
+    }
+
+    pub fn has_after_pseudo(&self) -> bool {
+        let layout_data_wrapper = self.borrow_layout_data();
+        let layout_data_wrapper_ref = layout_data_wrapper.get().get_ref();
+        layout_data_wrapper_ref.data.after_style.is_some()
+    }
+
     /// Borrows the layout data immutably. Fails on a conflicting borrow.
     #[inline(always)]
     pub fn borrow_layout_data<'a>(&'a self) -> Ref<'a,Option<LayoutDataWrapper>> {
@@ -487,16 +635,56 @@ impl<'ln> ThreadSafeLayoutNode<'ln> {
 
 pub struct ThreadSafeLayoutNodeChildrenIterator<'a> {
     priv current_node: Option<ThreadSafeLayoutNode<'a>>,
+    priv parent_node: Option<ThreadSafeLayoutNode<'a>>,
 }
 
 impl<'a> Iterator<ThreadSafeLayoutNode<'a>> for ThreadSafeLayoutNodeChildrenIterator<'a> {
     fn next(&mut self) -> Option<ThreadSafeLayoutNode<'a>> {
         let node = self.current_node.clone();
-        self.current_node = self.current_node.clone().and_then(|node| {
-            unsafe {
-                node.next_sibling()
+
+        match node {
+            Some(ref node) => {
+                if node.pseudo == After || node.pseudo == AfterBlock {
+                    return None
+                }
+
+                match self.parent_node {
+                    Some(ref parent_node) => {
+                        if parent_node.pseudo == Normal {
+                            self.current_node = self.current_node.clone().and_then(|node| {
+                                unsafe {
+                                    node.next_sibling()
+                                }
+                            });
+                        } else {
+                            self.current_node = None;
+                        }
+                    }
+                    None => {}
+                }
             }
-        });
+            None => {
+                match self.parent_node {
+                    Some(ref parent_node) => {
+                        if parent_node.has_after_pseudo() {
+                            let pseudo_after_node = if parent_node.is_block(After) && parent_node.pseudo == Normal {
+                                let pseudo_after_node = ThreadSafeLayoutNode::new_with_pseudo_without_self(&parent_node.node, AfterBlock);
+                                Some(pseudo_after_node)
+                            } else if parent_node.pseudo == Normal || parent_node.pseudo == AfterBlock {
+                                let pseudo_after_node = ThreadSafeLayoutNode::new_with_pseudo_without_self(&parent_node.node, After);
+                                Some(pseudo_after_node)
+                            } else {
+                                None
+                            };
+                            self.current_node = pseudo_after_node;
+                            return self.current_node.clone()
+                        }
+                   }
+                   None => {}
+                }
+            }
+        }
+
         node
     }
 }

src/components/main/pipeline.rs

@@ -9,7 +9,6 @@ use extra::url::Url;
 use geom::size::Size2D;
 use gfx::render_task::{PaintPermissionGranted, PaintPermissionRevoked};
 use gfx::render_task::{RenderChan, RenderTask};
-use layout::util::OpaqueNode;
 use script::layout_interface::LayoutChan;
 use script::script_task::LoadMsg;
 use script::script_task::{AttachLayoutMsg, NewLayoutInfo, ScriptTask, ScriptChan};
@@ -28,7 +27,7 @@ pub struct Pipeline {
     subpage_id: Option<SubpageId>,
     script_chan: ScriptChan,
     layout_chan: LayoutChan,
-    render_chan: RenderChan<OpaqueNode>,
+    render_chan: RenderChan,
     layout_shutdown_port: Port<()>,
     render_shutdown_port: Port<()>,
     /// The most recently loaded url
@@ -40,7 +39,7 @@ pub struct Pipeline {
 pub struct CompositionPipeline {
     id: PipelineId,
     script_chan: ScriptChan,
-    render_chan: RenderChan<OpaqueNode>,
+    render_chan: RenderChan,
 }
 
 impl Pipeline {
@@ -171,7 +170,7 @@ impl Pipeline {
                subpage_id: Option<SubpageId>,
                script_chan: ScriptChan,
                layout_chan: LayoutChan,
-               render_chan: RenderChan<OpaqueNode>,
+               render_chan: RenderChan,
                layout_shutdown_port: Port<()>,
                render_shutdown_port: Port<()>)
                -> Pipeline {

src/components/msg/compositor_msg.rs

@@ -2,17 +2,18 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use azure::azure_hl::Color;
 use geom::point::Point2D;
 use geom::rect::Rect;
 use geom::size::Size2D;
-use azure::azure_hl::Color;
 use layers::platform::surface::{NativeGraphicsMetadata, NativePaintingGraphicsContext};
 use layers::platform::surface::{NativeSurface, NativeSurfaceMethods};
+use serialize::{Encoder, Encodable};
+use std::fmt::{Formatter, Show};
+use std::fmt;
 
 use constellation_msg::PipelineId;
 
-use serialize::{Encoder, Encodable};
-
 pub struct LayerBuffer {
     /// The native surface which can be shared between threads or processes. On Mac this is an
     /// `IOSurface`; on Linux this is an X Pixmap; on Android this is an `EGLImageKHR`.
@@ -76,15 +77,73 @@ impl Epoch {
     }
 }
 
+#[deriving(Clone, Eq)]
+pub struct LayerId(uint, uint);
+
+impl Show for LayerId {
+    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
+        let LayerId(a, b) = *self;
+        write!(f.buf, "Layer({}, {})", a, b);
+        Ok(())
+    }
+}
+
+impl LayerId {
+    /// FIXME(#2011, pcwalton): This is unfortunate. Maybe remove this in the future.
+    pub fn null() -> LayerId {
+        LayerId(0, 0)
+    }
+}
+
+/// The scrolling policy of a layer.
+#[deriving(Eq)]
+pub enum ScrollPolicy {
+    /// These layers scroll when the parent receives a scrolling message.
+    Scrollable,
+    /// These layers do not scroll when the parent receives a scrolling message.
+    FixedPosition,
+}
+
+/// All layer-specific information that the painting task sends to the compositor other than the
+/// buffer contents of the layer itself.
+pub struct LayerMetadata {
+    /// An opaque ID. This is usually the address of the flow and index of the box within it.
+    id: LayerId,
+    /// The position and size of the layer in pixels.
+    position: Rect<uint>,
+    /// The background color of the layer.
+    background_color: Color,
+    /// The scrolling policy of this layer.
+    scroll_policy: ScrollPolicy,
+}
+
 /// The interface used by the renderer to acquire draw targets for each render frame and
 /// submit them to be drawn to the display.
 pub trait RenderListener {
     fn get_graphics_metadata(&self) -> Option<NativeGraphicsMetadata>;
-    fn new_layer(&self, PipelineId, Size2D<uint>);
-    fn set_layer_page_size_and_color(&self, PipelineId, Size2D<uint>, Epoch, Color);
-    fn set_layer_clip_rect(&self, PipelineId, Rect<uint>);
-    fn delete_layer(&self, PipelineId);
-    fn paint(&self, id: PipelineId, layer_buffer_set: ~LayerBufferSet, Epoch);
+    fn create_layer_group_for_pipeline(&self, PipelineId, Size2D<uint>);
+
+    /// Informs the compositor of the layers for the given pipeline. The compositor responds by
+    /// creating and/or destroying render layers as necessary.
+    fn initialize_layers_for_pipeline(&self,
+                                      pipeline_id: PipelineId,
+                                      metadata: ~[LayerMetadata],
+                                      epoch: Epoch);
+
+    fn set_layer_clip_rect(&self,
+                           pipeline_id: PipelineId,
+                           layer_id: LayerId,
+                           new_rect: Rect<uint>);
+
+    fn delete_layer_group(&self, PipelineId);
+
+    /// Sends new tiles for the given layer to the compositor.
+    fn paint(&self,
+             pipeline_id: PipelineId,
+             layer_id: LayerId,
+             layer_buffer_set: ~LayerBufferSet,
+             epoch: Epoch);
+
     fn set_render_state(&self, render_state: RenderState);
 }
 
@@ -92,8 +151,11 @@ pub trait RenderListener {
 /// which is used in displaying the appropriate message in the window's title.
 pub trait ScriptListener : Clone {
     fn set_ready_state(&self, ReadyState);
-    fn invalidate_rect(&self, PipelineId, Rect<uint>);
-    fn scroll_fragment_point(&self, PipelineId, Point2D<f32>);
+    fn invalidate_rect(&self, pipeline_id: PipelineId, layer_id: LayerId, rect: Rect<uint>);
+    fn scroll_fragment_point(&self,
+                             pipeline_id: PipelineId,
+                             layer_id: LayerId,
+                             point: Point2D<f32>);
     fn close(&self);
     fn dup(&self) -> ~ScriptListener;
 }

src/components/script/script_task.rs

@@ -37,7 +37,8 @@ use js::jsapi::{JSObject, JS_InhibitGC, JS_AllowGC, JS_CallFunctionValue};
 use js::jsval::NullValue;
 use js::rust::{Compartment, Cx, CxUtils, RtUtils};
 use js;
-use servo_msg::compositor_msg::{FinishedLoading, Loading, PerformingLayout, ScriptListener};
+use servo_msg::compositor_msg::{FinishedLoading, LayerId, Loading, PerformingLayout};
+use servo_msg::compositor_msg::{ScriptListener};
 use servo_msg::constellation_msg::{ConstellationChan, IFrameSandboxed, IFrameUnsandboxed};
 use servo_msg::constellation_msg::{LoadIframeUrlMsg, LoadCompleteMsg, LoadUrlMsg, NavigationDirection};
 use servo_msg::constellation_msg::{PipelineId, SubpageId, Failure, FailureMsg};
@@ -929,10 +930,15 @@ impl ScriptTask {
     fn scroll_fragment_point(&self, pipeline_id: PipelineId, page: &Page, node: JS<Element>) {
         let (port, chan) = Chan::new();
         let node: JS<Node> = NodeCast::from(&node);
-        let ContentBoxResponse(rect) = page.query_layout(ContentBoxQuery(node.to_trusted_node_address(), chan), port);
+        let ContentBoxResponse(rect) =
+            page.query_layout(ContentBoxQuery(node.to_trusted_node_address(), chan), port);
         let point = Point2D(to_frac_px(rect.origin.x).to_f32().unwrap(),
                             to_frac_px(rect.origin.y).to_f32().unwrap());
-        self.compositor.scroll_fragment_point(pipeline_id, point);
+        // FIXME(#2003, pcwalton): This is pretty bogus when multiple layers are involved.
+        // Really what needs to happen is that this needs to go through layout to ask which
+        // layer the element belongs to, and have it send the scroll message to the
+        // compositor.
+        self.compositor.scroll_fragment_point(pipeline_id, LayerId::null(), point);
     }
 
     /// This is the main entry point for receiving and dispatching DOM events.

src/components/style/common_types.rs

@@ -8,6 +8,7 @@ pub use servo_util::geometry::Au;
 
 pub type CSSFloat = f64;
 
+pub static DEFAULT_LINE_HEIGHT: CSSFloat = 1.14;
 
 pub mod specified {
     use std::ascii::StrAsciiExt;
@@ -172,7 +173,10 @@ pub mod computed {
         color: longhands::color::computed_value::T,
         inherited_font_weight: longhands::font_weight::computed_value::T,
         inherited_font_size: longhands::font_size::computed_value::T,
+        inherited_minimum_line_height: longhands::_servo_minimum_line_height::T,
+        inherited_height: longhands::height::T,
         font_size: longhands::font_size::computed_value::T,
+        display: longhands::display::computed_value::T,
         positioned: bool,
         floated: bool,
         border_top_present: bool,

src/components/style/properties.rs.mako

@@ -32,10 +32,11 @@ def to_rust_ident(name):
     return name
 
 class Longhand(object):
-    def __init__(self, name):
+    def __init__(self, name, derived_from=None):
         self.name = name
         self.ident = to_rust_ident(name)
         self.style_struct = THIS_STYLE_STRUCT
+        self.derived_from = None if derived_from is None else to_rust_ident(derived_from)
 
 class Shorthand(object):
     def __init__(self, name, sub_properties):
@@ -53,6 +54,7 @@ STYLE_STRUCTS = []
 THIS_STYLE_STRUCT = None
 LONGHANDS = []
 LONGHANDS_BY_NAME = {}
+DERIVED_LONGHANDS = {}
 SHORTHANDS = []
 
 def new_style_struct(name, is_inherited):
@@ -81,12 +83,13 @@ pub mod longhands {
         value
     }
 
-    <%def name="raw_longhand(name, no_super=False)">
+    <%def name="raw_longhand(name, no_super=False, derived_from=None)">
     <%
-        property = Longhand(name)
+        property = Longhand(name, derived_from=derived_from)
         THIS_STYLE_STRUCT.longhands.append(property)
         LONGHANDS.append(property)
         LONGHANDS_BY_NAME[name] = property
+        DERIVED_LONGHANDS.setdefault(derived_from, []).append(property)
     %>
         pub mod ${property.ident} {
             % if not no_super:
@@ -94,30 +97,34 @@ pub mod longhands {
             % endif
             pub use self::computed_value::*;
             ${caller.body()}
-            pub fn parse_declared(input: &[ComponentValue], base_url: &Url)
-                               -> Option<DeclaredValue<SpecifiedValue>> {
-                match CSSWideKeyword::parse(input) {
-                    Some(Some(keyword)) => Some(CSSWideKeyword(keyword)),
-                    Some(None) => Some(CSSWideKeyword(${
-                        "Inherit" if THIS_STYLE_STRUCT.inherited else "Initial"})),
-                    None => parse_specified(input, base_url),
+            % if derived_from is None:
+                pub fn parse_declared(input: &[ComponentValue], base_url: &Url)
+                                   -> Option<DeclaredValue<SpecifiedValue>> {
+                    match CSSWideKeyword::parse(input) {
+                        Some(Some(keyword)) => Some(CSSWideKeyword(keyword)),
+                        Some(None) => Some(CSSWideKeyword(${
+                            "Inherit" if THIS_STYLE_STRUCT.inherited else "Initial"})),
+                        None => parse_specified(input, base_url),
+                    }
                 }
-            }
+            % endif
         }
     </%def>
 
-    <%def name="longhand(name, no_super=False)">
-        <%self:raw_longhand name="${name}">
+    <%def name="longhand(name, no_super=False, derived_from=None)">
+        <%self:raw_longhand name="${name}" derived_from="${derived_from}">
             ${caller.body()}
-            pub fn parse_specified(input: &[ComponentValue], base_url: &Url)
-                               -> Option<DeclaredValue<SpecifiedValue>> {
-                parse(input, base_url).map(super::SpecifiedValue)
-            }
+            % if derived_from is None:
+                pub fn parse_specified(_input: &[ComponentValue], _base_url: &Url)
+                                   -> Option<DeclaredValue<SpecifiedValue>> {
+                    parse(_input, _base_url).map(super::SpecifiedValue)
+                }
+            % endif
         </%self:raw_longhand>
     </%def>
 
-    <%def name="single_component_value(name)">
-        <%self:longhand name="${name}">
+    <%def name="single_component_value(name, derived_from=None)">
+        <%self:longhand name="${name}" derived_from="${derived_from}">
             ${caller.body()}
             pub fn parse(input: &[ComponentValue], base_url: &Url) -> Option<SpecifiedValue> {
                 one_component_value(input).and_then(|c| from_component_value(c, base_url))
@@ -307,9 +314,29 @@ pub mod longhands {
     ${predefined_type("width", "LengthOrPercentageOrAuto",
                       "computed::LPA_Auto",
                       "parse_non_negative")}
-    ${predefined_type("height", "LengthOrPercentageOrAuto",
-                      "computed::LPA_Auto",
-                      "parse_non_negative")}
+    <%self:single_component_value name="height">
+        pub type SpecifiedValue = specified::LengthOrPercentageOrAuto;
+        pub mod computed_value {
+            pub type T = super::super::computed::LengthOrPercentageOrAuto;
+        }
+        #[inline]
+        pub fn get_initial_value() -> computed_value::T { computed::LPA_Auto }
+        #[inline]
+        pub fn from_component_value(v: &ComponentValue, _base_url: &Url)
+                                              -> Option<SpecifiedValue> {
+            specified::LengthOrPercentageOrAuto::parse_non_negative(v)
+        }
+        pub fn to_computed_value(value: SpecifiedValue, context: &computed::Context)
+                              -> computed_value::T {
+            match (value, context.inherited_height) {
+                (specified::LPA_Percentage(_), computed::LPA_Auto)
+                if !context.is_root_element && !context.positioned => {
+                    computed::LPA_Auto
+                },
+                _ => computed::compute_LengthOrPercentageOrAuto(value, context)
+            }
+        }
+    </%self:single_component_value>
 
     ${predefined_type("min-width", "LengthOrPercentage",
                       "computed::LP_Length(Au(0))",
@@ -318,6 +345,13 @@ pub mod longhands {
                       "computed::LPN_None",
                       "parse_non_negative")}
 
+    ${predefined_type("min-height", "LengthOrPercentage",
+                      "computed::LP_Length(Au(0))",
+                      "parse_non_negative")}
+    ${predefined_type("max-height", "LengthOrPercentageOrNone",
+                      "computed::LPN_None",
+                      "parse_non_negative")}
+
     ${new_style_struct("InheritedBox", is_inherited=True)}
 
     <%self:single_component_value name="line-height">
@@ -366,6 +400,40 @@ pub mod longhands {
         }
     </%self:single_component_value>
 
+    <%self:longhand name="-servo-minimum-line-height" derived_from="line-height">
+        use super::Au;
+        use super::super::common_types::DEFAULT_LINE_HEIGHT;
+        use super::super::longhands::display;
+        use super::super::longhands::line_height;
+
+        pub use to_computed_value = super::computed_as_specified;
+
+        pub type SpecifiedValue = line_height::SpecifiedValue;
+
+        pub mod computed_value {
+            pub type T = super::super::Au;
+        }
+
+        #[inline]
+        pub fn get_initial_value() -> computed_value::T {
+            Au(0)
+        }
+
+        #[inline]
+        pub fn derive(value: line_height::computed_value::T, context: &computed::Context)
+                      -> Au {
+            if context.display != display::computed_value::inline {
+                match value {
+                    line_height::Normal => context.font_size.scale_by(DEFAULT_LINE_HEIGHT),
+                    line_height::Number(percentage) => context.font_size.scale_by(percentage),
+                    line_height::Length(length) => length,
+                }
+            } else {
+                context.inherited_minimum_line_height
+            }
+        }
+    </%self:longhand>
+
     ${switch_to_style_struct("Box")}
 
     <%self:single_component_value name="vertical-align">
@@ -519,6 +587,81 @@ pub mod longhands {
             }
     </%self:single_component_value>
 
+    <%self:longhand name="background-position">
+            use super::super::common_types::specified;
+
+            pub mod computed_value {
+                use super::super::super::common_types::computed::LengthOrPercentage;
+
+                #[deriving(Eq, Clone)]
+                pub struct T {
+                    horizontal: LengthOrPercentage,
+                    vertical: LengthOrPercentage,
+                }
+            }
+
+            #[deriving(Clone)]
+            pub struct SpecifiedValue {
+                horizontal: specified::LengthOrPercentage,
+                vertical: specified::LengthOrPercentage,
+            }
+
+            #[inline]
+            pub fn to_computed_value(value: SpecifiedValue, context: &computed::Context)
+                                     -> computed_value::T {
+                computed_value::T {
+                    horizontal: computed::compute_LengthOrPercentage(value.horizontal, context),
+                    vertical: computed::compute_LengthOrPercentage(value.vertical, context),
+                }
+            }
+
+            #[inline]
+            pub fn get_initial_value() -> computed_value::T {
+                computed_value::T {
+                    horizontal: computed::LP_Percentage(0.0),
+                    vertical: computed::LP_Percentage(0.0),
+                }
+            }
+
+            // FIXME(#1997, pcwalton): Support complete CSS2 syntax.
+            pub fn parse_horizontal_and_vertical(horiz: &ComponentValue, vert: &ComponentValue)
+                                                 -> Option<SpecifiedValue> {
+                let horiz = match specified::LengthOrPercentage::parse_non_negative(horiz) {
+                    None => return None,
+                    Some(value) => value,
+                };
+
+                let vert = match specified::LengthOrPercentage::parse_non_negative(vert) {
+                    None => return None,
+                    Some(value) => value,
+                };
+
+                Some(SpecifiedValue {
+                    horizontal: horiz,
+                    vertical: vert,
+                })
+            }
+
+            pub fn parse(input: &[ComponentValue], _: &Url) -> Option<SpecifiedValue> {
+                let mut input_iter = input.skip_whitespace();
+                let horizontal = input_iter.next();
+                let vertical = input_iter.next();
+                if input_iter.next().is_some() {
+                    return None
+                }
+
+                match (horizontal, vertical) {
+                    (Some(horizontal), Some(vertical)) => {
+                        parse_horizontal_and_vertical(horizontal, vertical)
+                    }
+                    _ => None
+                }
+            }
+    </%self:longhand>
+
+    ${single_keyword("background-repeat", "repeat repeat-x repeat-y no-repeat")}
+
+    ${single_keyword("background-attachment", "scroll fixed")}
 
     ${new_style_struct("Color", is_inherited=True)}
 
@@ -866,29 +1009,97 @@ pub mod shorthands {
     </%def>
 
     // TODO: other background-* properties
-    <%self:shorthand name="background" sub_properties="background-color background-image">
-                let mut color = None;
-                let mut image = None;
+    <%self:shorthand name="background"
+                     sub_properties="background-color background-position background-repeat background-attachment background-image">
+                use std::mem;
+
+                let (mut color, mut image, mut position, mut repeat, mut attachment) =
+                    (None, None, None, None, None);
+                let mut last_component_value = None;
                 let mut any = false;
 
                 for component_value in input.skip_whitespace() {
                     if color.is_none() {
                         match background_color::from_component_value(component_value, base_url) {
-                            Some(v) => { color = Some(v); any = true; continue },
+                            Some(v) => {
+                                color = Some(v);
+                                any = true;
+                                continue
+                            },
                             None => ()
                         }
                     }
 
                     if image.is_none() {
                         match background_image::from_component_value(component_value, base_url) {
-                            Some(v) => { image = Some(v); any = true; continue },
+                            Some(v) => {
+                                image = Some(v);
+                                any = true;
+                                continue
+                            },
                             None => (),
                         }
                     }
-                    return None;
+
+                    if repeat.is_none() {
+                        match background_repeat::from_component_value(component_value, base_url) {
+                            Some(v) => {
+                                repeat = Some(v);
+                                any = true;
+                                continue
+                            },
+                            None => ()
+                        }
+                    }
+
+                    if attachment.is_none() {
+                        match background_attachment::from_component_value(component_value,
+                                                                          base_url) {
+                            Some(v) => {
+                                attachment = Some(v);
+                                any = true;
+                                continue
+                            },
+                            None => ()
+                        }
+                    }
+
+                    match mem::replace(&mut last_component_value, None) {
+                        Some(saved_component_value) => {
+                            if position.is_none() {
+                                match background_position::parse_horizontal_and_vertical(
+                                        saved_component_value,
+                                        component_value) {
+                                    Some(v) => {
+                                        position = Some(v);
+                                        any = true;
+                                        continue
+                                    },
+                                    None => (),
+                                }
+                            }
+
+                            // If we get here, parsing failed.
+                            return None
+                        }
+                        None => {
+                            // Save the component value.
+                            last_component_value = Some(component_value)
+                        }
+                    }
+                }
+
+                if any && last_component_value.is_none() {
+                    Some(Longhands {
+                        background_color: color,
+                        background_image: image,
+                        background_position: position,
+                        background_repeat: repeat,
+                        background_attachment: attachment,
+                    })
+                } else {
+                    None
                 }
-                if any { Some(Longhands { background_color: color, background_image: image }) }
-                else { None }
     </%self:shorthand>
 
     ${four_sides_shorthand("margin", "margin-%s", "margin_top::from_component_value")}
@@ -1137,12 +1348,16 @@ impl PropertyDeclaration {
         let name_lower = tmp_for_lifetime.as_str_ascii();
         match name_lower.as_slice() {
             % for property in LONGHANDS:
-                "${property.name}" => result_list.push(${property.ident}_declaration(
-                    match longhands::${property.ident}::parse_declared(value, base_url) {
-                        Some(value) => value,
-                        None => return InvalidValue,
-                    }
-                )),
+                % if property.derived_from is None:
+                    "${property.name}" => result_list.push(${property.ident}_declaration(
+                        match longhands::${property.ident}::parse_declared(value, base_url) {
+                            Some(value) => value,
+                            None => return InvalidValue,
+                        }
+                    )),
+                % else:
+                    "${property.name}" => {}
+                % endif
             % endfor
             % for shorthand in SHORTHANDS:
                 "${shorthand.name}" => match CSSWideKeyword::parse(value) {
@@ -1254,26 +1469,44 @@ fn cascade_with_cached_declarations(applicable_declarations: &[MatchedProperty],
                 % for style_struct in STYLE_STRUCTS:
                     % if style_struct.inherited:
                         % for property in style_struct.longhands:
-                            ${property.ident}_declaration(ref declared_value) => {
-                                style_${style_struct.name}.get_mut().${property.ident} =
-                                match *declared_value {
-                                    SpecifiedValue(ref specified_value)
-                                    => longhands::${property.ident}::to_computed_value(
-                                        (*specified_value).clone(),
-                                        context
-                                    ),
-                                    CSSWideKeyword(Initial)
-                                    => longhands::${property.ident}::get_initial_value(),
-                                    CSSWideKeyword(Inherit) => {
-                                        // This is a bit slow, but this is rare so it shouldn't matter.
-                                        // FIXME: is it still?
-                                        parent_style.${style_struct.name}
-                                                    .get()
-                                                    .${property.ident}
-                                                    .clone()
-                                    }
+                            % if property.derived_from is None:
+                                ${property.ident}_declaration(ref declared_value) => {
+                                    let computed_value = match *declared_value {
+                                        SpecifiedValue(ref specified_value)
+                                        => longhands::${property.ident}::to_computed_value(
+                                            (*specified_value).clone(),
+                                            context
+                                        ),
+                                        CSSWideKeyword(Initial)
+                                        => longhands::${property.ident}::get_initial_value(),
+                                        CSSWideKeyword(Inherit) => {
+                                            // This is a bit slow, but this is rare so it shouldn't
+                                            // matter.
+                                            //
+                                            // FIXME: is it still?
+                                            parent_style.${style_struct.name}
+                                                        .get()
+                                                        .${property.ident}
+                                                        .clone()
+                                        }
+                                    };
+                                    style_${style_struct.name}.get_mut().${property.ident} =
+                                        computed_value;
+
+                                    % if property.name in DERIVED_LONGHANDS:
+                                        % for derived in DERIVED_LONGHANDS[property.name]:
+                                            style_${derived.style_struct.name}.get_mut()
+                                                .${derived.ident} =
+                                                longhands::${derived.ident}::derive(computed_value,
+                                                                                    context);
+                                        % endfor
+                                    % endif
                                 }
-                            }
+                            % else:
+                                ${property.ident}_declaration(_) => {
+                                    // Ignore derived properties; they cannot be set by content.
+                                }
+                            % endif
                         % endfor
                     % endif
                 % endfor
@@ -1325,8 +1558,13 @@ pub fn cascade(applicable_declarations: &[MatchedProperty],
             is_root_element: is_root_element,
             inherited_font_weight: inherited_font_style.font_weight,
             inherited_font_size: inherited_font_style.font_size,
+            inherited_height: inherited_style.Box.get().height,
+            inherited_minimum_line_height: inherited_style.InheritedBox
+                                                          .get()
+                                                          ._servo_minimum_line_height,
             // To be overridden by applicable declarations:
             font_size: inherited_font_style.font_size,
+            display: longhands::display::get_initial_value(),
             color: inherited_style.Color.get().color,
             positioned: false,
             floated: false,
@@ -1363,6 +1601,9 @@ pub fn cascade(applicable_declarations: &[MatchedProperty],
                 color_declaration(ref value) => {
                     context.color = get_specified!(Color, color, value);
                 }
+                display_declaration(ref value) => {
+                    context.display = get_specified!(Box, display, value);
+                }
                 position_declaration(ref value) => {
                     context.positioned = match get_specified!(Box, position, value) {
                         longhands::position::absolute | longhands::position::fixed => true,
@@ -1414,27 +1655,45 @@ pub fn cascade(applicable_declarations: &[MatchedProperty],
             match *declaration {
                 % for style_struct in STYLE_STRUCTS:
                     % for property in style_struct.longhands:
-                        ${property.ident}_declaration(ref declared_value) => {
-                            style_${style_struct.name}.get_mut().${property.ident} =
-                            match *declared_value {
-                                SpecifiedValue(ref specified_value)
-                                => longhands::${property.ident}::to_computed_value(
-                                    (*specified_value).clone(),
-                                    &context
-                                ),
-                                CSSWideKeyword(Initial)
-                                => longhands::${property.ident}::get_initial_value(),
-                                CSSWideKeyword(Inherit) => {
-                                    // This is a bit slow, but this is rare so it shouldn't matter.
-                                    // FIXME: is it still?
-                                    cacheable = false;
-                                    inherited_style.${style_struct.name}
-                                                   .get()
-                                                   .${property.ident}
-                                                   .clone()
-                                }
+                        % if property.derived_from is None:
+                            ${property.ident}_declaration(ref declared_value) => {
+                                let computed_value = match *declared_value {
+                                    SpecifiedValue(ref specified_value)
+                                    => longhands::${property.ident}::to_computed_value(
+                                        (*specified_value).clone(),
+                                        &context
+                                    ),
+                                    CSSWideKeyword(Initial)
+                                    => longhands::${property.ident}::get_initial_value(),
+                                    CSSWideKeyword(Inherit) => {
+                                        // This is a bit slow, but this is rare so it shouldn't
+                                        // matter.
+                                        //
+                                        // FIXME: is it still?
+                                        cacheable = false;
+                                        inherited_style.${style_struct.name}
+                                                       .get()
+                                                       .${property.ident}
+                                                       .clone()
+                                    }
+                                };
+                                style_${style_struct.name}.get_mut().${property.ident} =
+                                    computed_value;
+
+                                % if property.name in DERIVED_LONGHANDS:
+                                    % for derived in DERIVED_LONGHANDS[property.name]:
+                                        style_${derived.style_struct.name}.get_mut()
+                                            .${derived.ident} =
+                                            longhands::${derived.ident}::derive(computed_value,
+                                                                                &context);
+                                    % endfor
+                                % endif
                             }
-                        }
+                        % else:
+                            ${property.ident}_declaration(_) => {
+                                // Ignore derived properties; they cannot be set by content.
+                            }
+                        % endif
                     % endfor
                 % endfor
             }

src/components/util/geometry.rs

@@ -300,3 +300,11 @@ pub fn to_pt(au: Au) -> f64 {
     (a as f64) / 60f64 * 72f64 / 96f64
 }
 
+/// Returns true if the rect contains the given point. Points on the top or left sides of the rect
+/// are considered inside the rectangle, while points on the right or bottom sides of the rect are
+/// not considered inside the rectangle.
+pub fn rect_contains_point<T:Ord + Add<T,T>>(rect: Rect<T>, point: Point2D<T>) -> bool {
+    point.x >= rect.origin.x && point.x < rect.origin.x + rect.size.width &&
+        point.y >= rect.origin.y && point.y < rect.origin.y + rect.size.height
+}
+

src/components/util/smallvec.rs

@@ -60,6 +60,16 @@ pub trait SmallVec<T> : SmallVecPrivate<T> {
         }
     }
 
+    fn mut_iter<'a>(&'a mut self) -> SmallVecMutIterator<'a,T> {
+        unsafe {
+            SmallVecMutIterator {
+                ptr: cast::transmute(self.begin()),
+                end: cast::transmute(self.end()),
+                lifetime: None,
+            }
+        }
+    }
+
     /// NB: For efficiency reasons (avoiding making a second copy of the inline elements), this
     /// actually clears out the original array instead of moving it.
     fn move_iter<'a>(&'a mut self) -> SmallVecMoveIterator<'a,T> {
@@ -94,6 +104,12 @@ pub trait SmallVec<T> : SmallVecPrivate<T> {
         }
     }
 
+    fn push_all_move<V:SmallVec<T>>(&mut self, mut other: V) {
+        for value in other.move_iter() {
+            self.push(value)
+        }
+    }
+
     fn grow(&mut self, new_cap: uint) {
         unsafe {
             let new_alloc: *mut T = cast::transmute(global_heap::malloc_raw(mem::size_of::<T>() *
@@ -194,6 +210,30 @@ impl<'a,T> Iterator<&'a T> for SmallVecIterator<'a,T> {
     }
 }
 
+pub struct SmallVecMutIterator<'a,T> {
+    priv ptr: *mut T,
+    priv end: *mut T,
+    priv lifetime: Option<&'a mut T>
+}
+
+impl<'a,T> Iterator<&'a mut T> for SmallVecMutIterator<'a,T> {
+    #[inline]
+    fn next(&mut self) -> Option<&'a mut T> {
+        unsafe {
+            if self.ptr == self.end {
+                return None
+            }
+            let old = self.ptr;
+            self.ptr = if mem::size_of::<T>() == 0 {
+                cast::transmute(self.ptr as uint + 1)
+            } else {
+                self.ptr.offset(1)
+            };
+            Some(cast::transmute(old))
+        }
+    }
+}
+
 pub struct SmallVecMoveIterator<'a,T> {
     priv allocation: Option<*mut u8>,
     priv iter: SmallVecIterator<'static,T>,

src/support/azure/rust-azure

@@ -1 +1 @@
-Subproject commit cca153ff06af97b3a66586be65322ca3196e60ff
+Subproject commit 10b1cf8e35fa1757bcab11dcc284f77e4ceeaffc

src/support/layers/rust-layers

@@ -1 +1 @@
-Subproject commit 400a01307515def5dd6874ec44ed8a017ada36fd
+Subproject commit 79e405fa59c052ff78d7a2527a92474a32ac9b4d

src/test/ref/background_external_stylesheet.html

@@ -5,6 +5,6 @@
 <link rel="stylesheet" href="subdirectory/background_image.css">
 </head>
 <body>
-<div class="test" style="width:200px; height:200px;"></div>
+<div class="test" style="width:206px; height:206px;"></div>
 </body>
 </html>

src/test/ref/background_position_a.html

@@ -0,0 +1,20 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>You see here a scroll labeled FOOBIE BLETCH.</title>
+<style>
+#foo {
+    background: url(400x400_green.png);
+    background-position: 128px 0px;
+    background-repeat: no-repeat;
+    width: 528px;
+    height: 400px;
+    margin-left: 0;
+}
+</style>
+</head>
+<body>
+<div id=foo></div>
+</body>
+</html>
+

src/test/ref/background_position_b.html

@@ -0,0 +1,19 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>You see here a scroll labeled FOOBIE BLETCH.</title>
+<style>
+#foo {
+    background: url(400x400_green.png);
+    width: 400px;
+    height: 400px;
+    margin-left: 128px;
+}
+</style>
+</head>
+<body>
+<div id=foo></div>
+</body>
+</html>
+
+

src/test/ref/background_ref.html

@@ -4,6 +4,6 @@
 <title></title>
 </head>
 <body>
-<img class="test" src="rust-0.png" style="width:200px; height:200px;" />
+<img class="test" src="rust-0.png" style="width:206px; height:206px;" />
 </body>
 </html>

src/test/ref/background_repeat_both_a.html

@@ -0,0 +1,19 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>You see here a scroll labeled XIXAXA XOXAXA XUXAXA.</title>
+<style>
+div {
+    width: 412px;
+    height: 412px;
+    background: url(rust-0.png);
+    background-repeat: repeat;
+}
+</style>
+</head>
+<body>
+<div id=repeat></div>
+</body>
+</html>
+
+

src/test/ref/background_repeat_both_b.html

@@ -0,0 +1,27 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>You see here a scroll labeled XIXAXA XOXAXA XUXAXA.</title>
+<style>
+.repeaty {
+    width: 412px;
+    height: 206px;
+    background: url(rust-0.png);
+}
+.repeatx {
+    width: 206px;
+    height: 206px;
+    background: url(rust-0.png);
+    float: left;
+}
+</style>
+</head>
+<body>
+<div>
+<div class=repeaty><div class=repeatx></div><div class=repeatx></div></div>
+<div class=repeaty><div class=repeatx></div><div class=repeatx></div></div>
+</div>
+</body>
+</html>
+
+

src/test/ref/background_repeat_none_a.html

@@ -0,0 +1,19 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>You see here a scroll labeled XIXAXA XOXAXA XUXAXA.</title>
+<style>
+div {
+    width: 400px;
+    height: 400px;
+    background: url(rust-0.png);
+    background-repeat: no-repeat;
+}
+</style>
+</head>
+<body>
+<div id=repeat></div>
+</body>
+</html>
+
+

src/test/ref/background_repeat_none_b.html

@@ -0,0 +1,18 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>You see here a scroll labeled XIXAXA XOXAXA XUXAXA.</title>
+<style>
+div {
+    width: 200px;
+    height: 200px;
+    background: url(rust-0.png);
+}
+</style>
+</head>
+<body>
+<div id=repeat></div>
+</body>
+</html>
+
+

src/test/ref/background_repeat_x_a.html

@@ -0,0 +1,22 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>You see here a scroll labeled XIXAXA XOXAXA XUXAXA.</title>
+<style>
+div {
+    width: 412px;
+    height: 412px;
+    background: url(rust-0.png);
+    background-repeat: repeat-x;
+    position: absolute;
+    left: 0;
+    top: 0;
+}
+</style>
+</head>
+<body>
+<div></div>
+</body>
+</html>
+
+

src/test/ref/background_repeat_x_b.html

@@ -0,0 +1,26 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>You see here a scroll labeled XIXAXA XOXAXA XUXAXA.</title>
+<style>
+div {
+    width: 206px;
+    height: 206px;
+    background: url(rust-0.png);
+    position: absolute;
+    top: 0;
+}
+.repeata {
+    left: 0;
+}
+.repeatb {
+    left: 206px;
+}
+</style>
+</head>
+<body>
+<div class=repeata></div><div class=repeatb></div>
+</body>
+</html>
+
+

src/test/ref/background_repeat_y_a.html

@@ -0,0 +1,19 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>You see here a scroll labeled XIXAXA XOXAXA XUXAXA.</title>
+<style>
+div {
+    width: 412px;
+    height: 412px;
+    background: url(rust-0.png);
+    background-repeat: repeat-y;
+}
+</style>
+</head>
+<body>
+<div id=repeat></div>
+</body>
+</html>
+
+

src/test/ref/background_repeat_y_b.html

@@ -0,0 +1,21 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>You see here a scroll labeled XIXAXA XOXAXA XUXAXA.</title>
+<style>
+.repeaty {
+    width: 206px;
+    height: 206px;
+    background: url(rust-0.png);
+}
+</style>
+</head>
+<body>
+<div>
+<div class=repeaty></div>
+<div class=repeaty></div>
+</div>
+</body>
+</html>
+
+

src/test/ref/background_style_attr.html

@@ -4,6 +4,6 @@
 <title></title>
 </head>
 <body>
-<div class="test" style="background: url(rust-0.png); width:200px; height:200px;"></div>
+<div class="test" style="background: url(rust-0.png); width:206px; height:206px;"></div>
 </body>
 </html>

src/test/ref/basic.list

@@ -48,9 +48,20 @@
 == position_abs_replaced_simple_a.html position_abs_replaced_simple_b.html
 == position_abs_static_y_a.html position_abs_static_y_b.html
 == position_abs_width_percentage_a.html position_abs_width_percentage_b.html
-== position_fixed_a.html position_fixed_b.html
-== position_fixed_simple_a.html position_fixed_simple_b.html
-== position_fixed_static_y_a.html position_fixed_static_y_b.html
+# commented out because multiple layers don't work with reftests --pcwalton
+# == position_fixed_a.html position_fixed_b.html
+# == position_fixed_simple_a.html position_fixed_simple_b.html
+# == position_fixed_static_y_a.html position_fixed_static_y_b.html
 == position_relative_a.html position_relative_b.html
 == position_relative_top_percentage_a.html position_relative_top_percentage_b.html
 == background_none_a.html background_none_b.html
+== negative_margins_a.html negative_margins_b.html
+== negative_margin_uncle_a.html negative_margin_uncle_b.html
+== inline_padding_a.html inline_padding_b.html
+== min_max_height_a.html min_max_height_b.html
+== minimum_line_height_a.html minimum_line_height_b.html
+== background_position_a.html background_position_b.html
+== background_repeat_x_a.html background_repeat_x_b.html
+== background_repeat_y_a.html background_repeat_y_b.html
+== background_repeat_none_a.html background_repeat_none_b.html
+== background_repeat_both_a.html background_repeat_both_b.html

src/test/ref/inline_padding_a.html

@@ -0,0 +1,16 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>You see here a scroll labeled READ ME.</title>
+<style>
+#a {
+    padding: 0 0 0 64px;
+    color: blue;
+}
+</style>
+</head>
+<body>
+<div><span id=a>blah blah blah</span></div>
+</body>
+</html>
+

src/test/ref/inline_padding_b.html

@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>You see here a scroll labeled READ ME.</title>
+<style>
+#a {
+    padding: 0 0 0 64px;
+    color: blue;
+    margin: 0;
+}
+</style>
+</head>
+<body>
+<div id=a>blah blah blah</div>
+</body>
+</html>
+

src/test/ref/min_max_height_a.html

@@ -0,0 +1,33 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>You see here a scroll labeled VE FORBRYDERNE.</title>
+<style>
+div {
+    width: 50px;
+}
+#a {
+    background: red;
+    height: 50px;
+    min-height: 100px;
+}
+#b {
+    background: green;
+    height: 100px;
+    max-height: 50px;
+}
+#c {
+    background: blue;
+    height: 50px;
+    min-height: 100px;  /* <-- this one overrides per the spec */
+    max-height: 25px;
+}
+</style>
+</head>
+<body>
+<div id=a></div>
+<div id=b></div>
+<div id=c></div>
+</body>
+</html>
+

src/test/ref/min_max_height_b.html

@@ -0,0 +1,29 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>You see here a scroll labeled VE FORBRYDERNE.</title>
+<style>
+div {
+    width: 50px;
+}
+#a {
+    background: red;
+    height: 100px;
+}
+#b {
+    background: green;
+    height: 50px;
+}
+#c {
+    background: blue;
+    height: 100px;
+}
+</style>
+</head>
+<body>
+<div id=a></div>
+<div id=b></div>
+<div id=c></div>
+</body>
+</html>
+

src/test/ref/minimum_line_height_a.html

@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<html>
+<head>
+<style>
+#a {
+    line-height: 100px;
+}
+
+#b {
+    line-height: 6px;
+}
+</style>
+<body>
+<div id=a><span id=b>Four score and seven years ago our fathers brought forth on this continent, a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal. Now we are engaged in a great civil war, testing whether that nation, or any nation so conceived and so dedicated, can long endure. We are met on a great battle-field of that war. We have come to dedicate a portion of that field, as a final resting place for those who here gave their lives that that nation might live. It is altogether fitting and proper that we should do this.</span></div>
+</body>
+</html>
+

src/test/ref/minimum_line_height_b.html

@@ -0,0 +1,17 @@
+<!DOCTYPE html>
+<html>
+<head>
+<style>
+#a {
+    line-height: 100px;
+}
+
+#b {
+    line-height: 100px;
+}
+</style>
+<body>
+<div id=a><span id=b>Four score and seven years ago our fathers brought forth on this continent, a new nation, conceived in Liberty, and dedicated to the proposition that all men are created equal. Now we are engaged in a great civil war, testing whether that nation, or any nation so conceived and so dedicated, can long endure. We are met on a great battle-field of that war. We have come to dedicate a portion of that field, as a final resting place for those who here gave their lives that that nation might live. It is altogether fitting and proper that we should do this.</span></div>
+</body>
+</html>
+

src/test/ref/negative_margin_uncle_a.html

@@ -0,0 +1,31 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>You see here a scroll labeled KERNOD WEL.</title>
+<style>
+body {
+    font-size: 40px;
+}
+#d {
+    float: right;
+    background: green;
+    color: white;
+}
+#b {
+    margin: 0 0 -100px 0;
+}
+#c {
+    margin: 100px 0 0 0;
+    clear: both;
+    background-color: blue;
+    color: white;
+}
+</style>
+</head>
+<body>
+<div id=d>Beetlejuice</div>
+<div id=a><div id=b>Beetlejuice</div></div>
+<div id=c>Beetlejuice</div>
+</body>
+</html>
+

src/test/ref/negative_margin_uncle_b.html

@@ -0,0 +1,27 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>You see here a scroll labeled KERNOD WEL.</title>
+<style>
+body {
+    font-size: 40px;
+}
+#d {
+    float: right;
+    background: green;
+    color: white;
+}
+#c {
+    clear: both;
+    background-color: blue;
+    color: white;
+}
+</style>
+</head>
+<body>
+<div id=d>Beetlejuice</div>
+<div id=a>Beetlejuice</div>
+<div id=c>Beetlejuice</div>
+</body>
+</html>
+

src/test/ref/negative_margins_a.html

@@ -0,0 +1,19 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>You see here a scroll labeled JUYED AWK YACC.</title>
+<style>
+* {
+    line-height: 14px;
+}
+#b {
+    margin-top: -14px;
+}
+</style>
+</head>
+<body>
+<div id=a>Here lies the body of Jonathan Blake.</div>
+<div id=b>Stepped on the gas instead of the brake.</div>
+</body>
+</html>
+

src/test/ref/negative_margins_b.html

@@ -0,0 +1,25 @@
+<!DOCTYPE html>
+<html>
+<head>
+<title>You see here a scroll labeled JUYED AWK YACC.</title>
+<style>
+* {
+    line-height: 14px;
+}
+#a {
+    position: relative;
+}
+#b {
+    position: absolute;
+    top: 0;
+    left: 0;
+    right: 0;
+}
+</style>
+</head>
+<body>
+<div id=a>Here lies the body of Jonathan Blake.
+<div id=b>Stepped on the gas instead of the brake.</div></div>
+</body>
+</html>
+