Implement ScrollTop and ScrollLeft getters:

Add new compositor message to get scroll_offset;
Add new layout query for computed value of overflow-x/y;
Implement layer_id method for ThreadSafeLayoutNode;
Add new layout query for layer_id;
Implement script interface for getting scrollTop and scrollLeft, as well as relavant helper functions.

components/layout/layout_thread.rs

@@ -45,10 +45,11 @@ use profile_traits::mem::{self, Report, ReportKind, ReportsChan};
 use profile_traits::time::{TimerMetadataFrameType, TimerMetadataReflowType};
 use profile_traits::time::{self, TimerMetadata, profile};
 use query::{LayoutRPCImpl, process_content_box_request, process_content_boxes_request};
-use query::{process_node_geometry_request, process_node_scroll_area_request, process_offset_parent_query};
-use query::{process_resolved_style_request, process_margin_style_query};
+use query::{process_node_geometry_request, process_node_layer_id_request, process_node_scroll_area_request};
+use query::{process_node_overflow_request, process_resolved_style_request, process_margin_style_query};
+use query::{process_offset_parent_query};
 use script::dom::node::OpaqueStyleAndLayoutData;
-use script::layout_interface::{LayoutRPC, OffsetParentResponse, MarginStyleResponse};
+use script::layout_interface::{LayoutRPC, OffsetParentResponse, NodeOverflowResponse, MarginStyleResponse};
 use script::layout_interface::{Msg, NewLayoutThreadInfo, Reflow, ReflowQueryType};
 use script::layout_interface::{ScriptLayoutChan, ScriptReflow};
 use script::reporter::CSSErrorReporter;
@@ -117,9 +118,14 @@ pub struct LayoutThreadData {
     /// A queued response for the client {top, left, width, height} of a node in pixels.
     pub client_rect_response: Rect<i32>,
 
+    pub layer_id_response: Option<LayerId>,
+
     /// A queued response for the node at a given point
     pub hit_test_response: (Option<DisplayItemMetadata>, bool),
 
+    /// A pair of overflow property in x and y
+    pub overflow_response: NodeOverflowResponse,
+
     /// A queued response for the scroll {top, left, width, height} of a node in pixels.
     pub scroll_area_response: Rect<i32>,
 
@@ -463,8 +469,10 @@ impl LayoutThread {
                     content_box_response: Rect::zero(),
                     content_boxes_response: Vec::new(),
                     client_rect_response: Rect::zero(),
+                    layer_id_response: None,
                     hit_test_response: (None, false),
                     scroll_area_response: Rect::zero(),
+                    overflow_response: NodeOverflowResponse(None),
                     resolved_style_response: None,
                     offset_parent_response: OffsetParentResponse::empty(),
                     margin_style_response: MarginStyleResponse::empty(),
@@ -1015,9 +1023,15 @@ impl LayoutThread {
                     ReflowQueryType::NodeGeometryQuery(_) => {
                         rw_data.client_rect_response = Rect::zero();
                     },
+                    ReflowQueryType::NodeLayerIdQuery(_) => {
+                        rw_data.layer_id_response = None;
+                    },
                     ReflowQueryType::NodeScrollGeometryQuery(_) => {
                         rw_data.scroll_area_response = Rect::zero();
                     },
+                    ReflowQueryType::NodeOverflowQuery(_) => {
+                        rw_data.overflow_response = NodeOverflowResponse(None);
+                    },
                     ReflowQueryType::ResolvedStyleQuery(_, _, _) => {
                         rw_data.resolved_style_response = None;
                     },
@@ -1177,6 +1191,14 @@ impl LayoutThread {
                     let node = unsafe { ServoLayoutNode::new(&node) };
                     rw_data.scroll_area_response = process_node_scroll_area_request(node, &mut root_flow);
                 },
+                ReflowQueryType::NodeOverflowQuery(node) => {
+                    let node = unsafe { ServoLayoutNode::new(&node) };
+                    rw_data.overflow_response = process_node_overflow_request(node);
+                },
+                ReflowQueryType::NodeLayerIdQuery(node) => {
+                    let node = unsafe { ServoLayoutNode::new(&node) };
+                    rw_data.layer_id_response = Some(process_node_layer_id_request(node));
+                },
                 ReflowQueryType::ResolvedStyleQuery(node, ref pseudo, ref property) => {
                     let node = unsafe { ServoLayoutNode::new(&node) };
                     rw_data.resolved_style_response =

components/layout/query.rs

@@ -13,11 +13,12 @@ use flow;
 use flow_ref::FlowRef;
 use fragment::{Fragment, FragmentBorderBoxIterator, SpecificFragmentInfo};
 use gfx::display_list::OpaqueNode;
+use gfx_traits::{LayerId};
 use layout_thread::LayoutThreadData;
 use msg::constellation_msg::ConstellationChan;
 use opaque_node::OpaqueNodeMethods;
-use script::layout_interface::{ContentBoxResponse, ContentBoxesResponse, NodeGeometryResponse};
-use script::layout_interface::{HitTestResponse, LayoutRPC, OffsetParentResponse};
+use script::layout_interface::{ContentBoxResponse, NodeOverflowResponse, ContentBoxesResponse, NodeGeometryResponse};
+use script::layout_interface::{HitTestResponse, LayoutRPC, OffsetParentResponse, NodeLayerIdResponse};
 use script::layout_interface::{ResolvedStyleResponse, ScriptLayoutChan, MarginStyleResponse};
 use script_traits::LayoutMsg as ConstellationMsg;
 use script_traits::UntrustedNodeAddress;
@@ -112,12 +113,23 @@ impl LayoutRPC for LayoutRPCImpl {
         }
     }
 
+    fn node_overflow(&self) -> NodeOverflowResponse {
+        NodeOverflowResponse(self.0.lock().unwrap().overflow_response.0)
+    }
+
     fn node_scroll_area(&self) -> NodeGeometryResponse {
         NodeGeometryResponse {
             client_rect: self.0.lock().unwrap().scroll_area_response
         }
     }
 
+    fn node_layer_id(&self) -> NodeLayerIdResponse {
+        NodeLayerIdResponse {
+            layer_id: self.0.lock().unwrap().layer_id_response
+                          .expect("layer_id is not correctly fetched, see PR #9968")
+        }
+    }
+
     /// Retrieves the resolved value for a CSS style property.
     fn resolved_style(&self) -> ResolvedStyleResponse {
         let &LayoutRPCImpl(ref rw_data) = self;
@@ -425,6 +437,7 @@ impl FragmentBorderBoxIterator for UnioningFragmentScrollAreaIterator {
         let bottom_padding = (border_box.size.height - bottom_border - top_border).to_px();
         let top_padding = top_border.to_px();
         let left_padding = left_border.to_px();
+
         match self.level {
             Some(start_level) if level <= start_level => { self.is_child = false; }
             Some(_) => {
@@ -517,6 +530,11 @@ pub fn process_node_geometry_request<N: LayoutNode>(requested_node: N, layout_ro
     iterator.client_rect
 }
 
+pub fn process_node_layer_id_request<N: LayoutNode>(requested_node: N) -> LayerId {
+    let layout_node = requested_node.to_threadsafe();
+    layout_node.layer_id()
+}
+
 pub fn process_node_scroll_area_request< N: LayoutNode>(requested_node: N, layout_root: &mut FlowRef)
         -> Rect<i32> {
     let mut iterator = UnioningFragmentScrollAreaIterator::new(requested_node.opaque());
@@ -691,6 +709,14 @@ pub fn process_offset_parent_query<N: LayoutNode>(requested_node: N, layout_root
     }
 }
 
+pub fn process_node_overflow_request<N: LayoutNode>(requested_node: N) -> NodeOverflowResponse {
+    let layout_node = requested_node.to_threadsafe();
+    let style = &*layout_node.style();
+    let style_box = style.get_box();
+
+    NodeOverflowResponse(Some((Point2D::new(style_box.overflow_x, style_box.overflow_y.0))))
+}
+
 pub fn process_margin_style_query<N: LayoutNode>(requested_node: N)
         -> MarginStyleResponse {
     let layout_node = requested_node.to_threadsafe();

components/layout/wrapper.rs

@@ -34,6 +34,7 @@ use core::nonzero::NonZero;
 use data::{LayoutDataFlags, PrivateLayoutData};
 use gfx::display_list::OpaqueNode;
 use gfx::text::glyph::CharIndex;
+use gfx_traits::{LayerId, LayerType};
 use incremental::RestyleDamage;
 use msg::constellation_msg::PipelineId;
 use opaque_node::OpaqueNodeMethods;
@@ -851,6 +852,21 @@ pub trait ThreadSafeLayoutNode : Clone + Copy + Sized + PartialEq {
     fn iframe_pipeline_id(&self) -> PipelineId;
 
     fn get_colspan(&self) -> u32;
+
+    fn layer_id(&self) -> LayerId {
+        let layer_type = match self.get_pseudo_element_type() {
+            PseudoElementType::Normal => LayerType::FragmentBody,
+            PseudoElementType::Before(_) => LayerType::BeforePseudoContent,
+            PseudoElementType::After(_) => LayerType::AfterPseudoContent,
+            PseudoElementType::DetailsSummary(_) => LayerType::FragmentBody,
+            PseudoElementType::DetailsContent(_) => LayerType::FragmentBody,
+        };
+        LayerId::new_of_type(layer_type, self.opaque().id() as usize)
+    }
+
+    fn layer_id_for_overflow_scroll(&self) -> LayerId {
+        LayerId::new_of_type(LayerType::OverflowScroll, self.opaque().id() as usize)
+    }
 }
 
 // This trait is only public so that it can be implemented by the gecko wrapper.