servo/components/layout/query.rs
Martin Robinson 9fd2df5c09 Properly handle scroll offsets in hit testing
Scroll roots are no longer nested containers holding items, so instead
we need to track the offsets of each, carefully handling fixed position
items and stacking contexts that create new reference frames.
Additionally, we remove the complexity of the pre-computed page scroll
offset, instead opting to send script scrolls to the layout task in
order to more quickly have a ScrollState there that matches the
script's idea of the scroll world.

Fixes #16405.
2017-05-16 15:27:09 +02:00

888 lines
36 KiB
Rust

/* This Source Code Form is subject to the terms of the Mozilla Public
* 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/. */
//! Utilities for querying the layout, as needed by the layout thread.
use app_units::Au;
use construct::ConstructionResult;
use context::LayoutContext;
use euclid::point::Point2D;
use euclid::rect::Rect;
use euclid::size::Size2D;
use flow::{self, Flow};
use fragment::{Fragment, FragmentBorderBoxIterator, SpecificFragmentInfo};
use gfx::display_list::{DisplayItemMetadata, DisplayList, OpaqueNode, ScrollOffsetMap};
use inline::LAST_FRAGMENT_OF_ELEMENT;
use ipc_channel::ipc::IpcSender;
use msg::constellation_msg::PipelineId;
use opaque_node::OpaqueNodeMethods;
use script_layout_interface::rpc::{ContentBoxResponse, ContentBoxesResponse};
use script_layout_interface::rpc::{HitTestResponse, LayoutRPC};
use script_layout_interface::rpc::{MarginStyleResponse, NodeGeometryResponse};
use script_layout_interface::rpc::{NodeOverflowResponse, OffsetParentResponse};
use script_layout_interface::rpc::{NodeScrollRootIdResponse, ResolvedStyleResponse, TextIndexResponse};
use script_layout_interface::wrapper_traits::{LayoutNode, ThreadSafeLayoutElement, ThreadSafeLayoutNode};
use script_traits::LayoutMsg as ConstellationMsg;
use script_traits::UntrustedNodeAddress;
use sequential;
use std::cmp::{min, max};
use std::ops::Deref;
use std::sync::{Arc, Mutex};
use style::computed_values;
use style::context::{StyleContext, ThreadLocalStyleContext};
use style::dom::TElement;
use style::logical_geometry::{WritingMode, BlockFlowDirection, InlineBaseDirection};
use style::properties::{style_structs, PropertyId, PropertyDeclarationId, LonghandId};
use style::properties::longhands::{display, position};
use style::selector_parser::PseudoElement;
use style_traits::ToCss;
use style_traits::cursor::Cursor;
use webrender_traits::ClipId;
use wrapper::{LayoutNodeHelpers, LayoutNodeLayoutData};
/// Mutable data belonging to the LayoutThread.
///
/// This needs to be protected by a mutex so we can do fast RPCs.
pub struct LayoutThreadData {
/// The channel on which messages can be sent to the constellation.
pub constellation_chan: IpcSender<ConstellationMsg>,
/// The root stacking context.
pub display_list: Option<Arc<DisplayList>>,
/// A queued response for the union of the content boxes of a node.
pub content_box_response: Option<Rect<Au>>,
/// A queued response for the content boxes of a node.
pub content_boxes_response: Vec<Rect<Au>>,
/// A queued response for the client {top, left, width, height} of a node in pixels.
pub client_rect_response: Rect<i32>,
/// A queued response for the node at a given point
pub hit_test_response: (Option<DisplayItemMetadata>, bool),
/// A queued response for the scroll root id for a given node.
pub scroll_root_id_response: Option<ClipId>,
/// 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>,
/// A queued response for the resolved style property of an element.
pub resolved_style_response: String,
/// A queued response for the offset parent/rect of a node.
pub offset_parent_response: OffsetParentResponse,
/// A queued response for the offset parent/rect of a node.
pub margin_style_response: MarginStyleResponse,
/// Scroll offsets of scrolling regions.
pub scroll_offsets: ScrollOffsetMap,
/// Index in a text fragment. We need this do determine the insertion point.
pub text_index_response: TextIndexResponse,
/// A queued response for the list of nodes at a given point.
pub nodes_from_point_response: Vec<UntrustedNodeAddress>,
}
pub struct LayoutRPCImpl(pub Arc<Mutex<LayoutThreadData>>);
// https://drafts.csswg.org/cssom-view/#overflow-directions
fn overflow_direction(writing_mode: &WritingMode) -> OverflowDirection {
match (writing_mode.block_flow_direction(), writing_mode.inline_base_direction()) {
(BlockFlowDirection::TopToBottom, InlineBaseDirection::LeftToRight) |
(BlockFlowDirection::LeftToRight, InlineBaseDirection::LeftToRight) => OverflowDirection::RightAndDown,
(BlockFlowDirection::TopToBottom, InlineBaseDirection::RightToLeft) |
(BlockFlowDirection::RightToLeft, InlineBaseDirection::LeftToRight) => OverflowDirection::LeftAndDown,
(BlockFlowDirection::RightToLeft, InlineBaseDirection::RightToLeft) => OverflowDirection::LeftAndUp,
(BlockFlowDirection::LeftToRight, InlineBaseDirection::RightToLeft) => OverflowDirection::RightAndUp
}
}
impl LayoutRPC for LayoutRPCImpl {
// 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`.
fn content_box(&self) -> ContentBoxResponse {
let &LayoutRPCImpl(ref rw_data) = self;
let rw_data = rw_data.lock().unwrap();
ContentBoxResponse(rw_data.content_box_response)
}
/// Requests the dimensions of all the content boxes, as in the `getClientRects()` call.
fn content_boxes(&self) -> ContentBoxesResponse {
let &LayoutRPCImpl(ref rw_data) = self;
let rw_data = rw_data.lock().unwrap();
ContentBoxesResponse(rw_data.content_boxes_response.clone())
}
/// Requests the node containing the point of interest.
fn hit_test(&self) -> HitTestResponse {
let &LayoutRPCImpl(ref rw_data) = self;
let rw_data = rw_data.lock().unwrap();
let &(ref result, update_cursor) = &rw_data.hit_test_response;
if update_cursor {
// Compute the new cursor.
let cursor = match *result {
None => Cursor::Default,
Some(dim) => dim.pointing.unwrap(),
};
rw_data.constellation_chan.send(ConstellationMsg::SetCursor(cursor)).unwrap();
}
HitTestResponse {
node_address: result.map(|dim| dim.node.to_untrusted_node_address()),
}
}
fn nodes_from_point_response(&self) -> Vec<UntrustedNodeAddress> {
let &LayoutRPCImpl(ref rw_data) = self;
let rw_data = rw_data.lock().unwrap();
rw_data.nodes_from_point_response.clone()
}
fn node_geometry(&self) -> NodeGeometryResponse {
let &LayoutRPCImpl(ref rw_data) = self;
let rw_data = rw_data.lock().unwrap();
NodeGeometryResponse {
client_rect: rw_data.client_rect_response
}
}
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_scroll_root_id(&self) -> NodeScrollRootIdResponse {
NodeScrollRootIdResponse(self.0.lock()
.unwrap().scroll_root_id_response
.expect("scroll_root_id is not correctly fetched"))
}
/// Retrieves the resolved value for a CSS style property.
fn resolved_style(&self) -> ResolvedStyleResponse {
let &LayoutRPCImpl(ref rw_data) = self;
let rw_data = rw_data.lock().unwrap();
ResolvedStyleResponse(rw_data.resolved_style_response.clone())
}
fn offset_parent(&self) -> OffsetParentResponse {
let &LayoutRPCImpl(ref rw_data) = self;
let rw_data = rw_data.lock().unwrap();
rw_data.offset_parent_response.clone()
}
fn margin_style(&self) -> MarginStyleResponse {
let &LayoutRPCImpl(ref rw_data) = self;
let rw_data = rw_data.lock().unwrap();
rw_data.margin_style_response.clone()
}
fn text_index(&self) -> TextIndexResponse {
let &LayoutRPCImpl(ref rw_data) = self;
let rw_data = rw_data.lock().unwrap();
rw_data.text_index_response.clone()
}
}
struct UnioningFragmentBorderBoxIterator {
node_address: OpaqueNode,
rect: Option<Rect<Au>>,
}
impl UnioningFragmentBorderBoxIterator {
fn new(node_address: OpaqueNode) -> UnioningFragmentBorderBoxIterator {
UnioningFragmentBorderBoxIterator {
node_address: node_address,
rect: None
}
}
}
impl FragmentBorderBoxIterator for UnioningFragmentBorderBoxIterator {
fn process(&mut self, _: &Fragment, _: i32, border_box: &Rect<Au>) {
self.rect = match self.rect {
Some(rect) => {
Some(rect.union(border_box))
}
None => {
Some(*border_box)
}
};
}
fn should_process(&mut self, fragment: &Fragment) -> bool {
fragment.contains_node(self.node_address)
}
}
struct CollectingFragmentBorderBoxIterator {
node_address: OpaqueNode,
rects: Vec<Rect<Au>>,
}
impl CollectingFragmentBorderBoxIterator {
fn new(node_address: OpaqueNode) -> CollectingFragmentBorderBoxIterator {
CollectingFragmentBorderBoxIterator {
node_address: node_address,
rects: Vec::new(),
}
}
}
impl FragmentBorderBoxIterator for CollectingFragmentBorderBoxIterator {
fn process(&mut self, _: &Fragment, _: i32, border_box: &Rect<Au>) {
self.rects.push(*border_box);
}
fn should_process(&mut self, fragment: &Fragment) -> bool {
fragment.contains_node(self.node_address)
}
}
enum Side {
Left,
Right,
Bottom,
Top
}
enum MarginPadding {
Margin,
Padding
}
enum PositionProperty {
Left,
Right,
Top,
Bottom,
Width,
Height,
}
#[derive(Debug)]
enum OverflowDirection {
RightAndDown,
LeftAndDown,
LeftAndUp,
RightAndUp,
}
struct PositionRetrievingFragmentBorderBoxIterator {
node_address: OpaqueNode,
result: Option<Au>,
position: Point2D<Au>,
property: PositionProperty,
}
impl PositionRetrievingFragmentBorderBoxIterator {
fn new(node_address: OpaqueNode,
property: PositionProperty,
position: Point2D<Au>) -> PositionRetrievingFragmentBorderBoxIterator {
PositionRetrievingFragmentBorderBoxIterator {
node_address: node_address,
position: position,
property: property,
result: None,
}
}
}
impl FragmentBorderBoxIterator for PositionRetrievingFragmentBorderBoxIterator {
fn process(&mut self, fragment: &Fragment, _: i32, border_box: &Rect<Au>) {
let border_padding = fragment.border_padding.to_physical(fragment.style.writing_mode);
self.result =
Some(match self.property {
PositionProperty::Left => self.position.x,
PositionProperty::Top => self.position.y,
PositionProperty::Width => border_box.size.width - border_padding.horizontal(),
PositionProperty::Height => border_box.size.height - border_padding.vertical(),
// TODO: the following 2 calculations are completely wrong.
// They should return the difference between the parent's and this
// fragment's border boxes.
PositionProperty::Right => border_box.max_x() + self.position.x,
PositionProperty::Bottom => border_box.max_y() + self.position.y,
});
}
fn should_process(&mut self, fragment: &Fragment) -> bool {
fragment.contains_node(self.node_address)
}
}
struct MarginRetrievingFragmentBorderBoxIterator {
node_address: OpaqueNode,
result: Option<Au>,
writing_mode: WritingMode,
margin_padding: MarginPadding,
side: Side,
}
impl MarginRetrievingFragmentBorderBoxIterator {
fn new(node_address: OpaqueNode, side: Side, margin_padding:
MarginPadding, writing_mode: WritingMode) -> MarginRetrievingFragmentBorderBoxIterator {
MarginRetrievingFragmentBorderBoxIterator {
node_address: node_address,
side: side,
margin_padding: margin_padding,
result: None,
writing_mode: writing_mode,
}
}
}
impl FragmentBorderBoxIterator for MarginRetrievingFragmentBorderBoxIterator {
fn process(&mut self, fragment: &Fragment, _: i32, _: &Rect<Au>) {
let rect = match self.margin_padding {
MarginPadding::Margin => &fragment.margin,
MarginPadding::Padding => &fragment.border_padding
};
self.result = Some(match self.side {
Side::Left => rect.left(self.writing_mode),
Side::Right => rect.right(self.writing_mode),
Side::Bottom => rect.bottom(self.writing_mode),
Side::Top => rect.top(self.writing_mode)
});
}
fn should_process(&mut self, fragment: &Fragment) -> bool {
fragment.contains_node(self.node_address)
}
}
pub fn process_content_box_request<N: LayoutNode>(
requested_node: N, layout_root: &mut Flow) -> Option<Rect<Au>> {
// FIXME(pcwalton): This has not been updated to handle the stacking context relative
// stuff. So the position is wrong in most cases.
let mut iterator = UnioningFragmentBorderBoxIterator::new(requested_node.opaque());
sequential::iterate_through_flow_tree_fragment_border_boxes(layout_root, &mut iterator);
iterator.rect
}
pub fn process_content_boxes_request<N: LayoutNode>(requested_node: N, layout_root: &mut Flow)
-> Vec<Rect<Au>> {
// FIXME(pcwalton): This has not been updated to handle the stacking context relative
// stuff. So the position is wrong in most cases.
let mut iterator = CollectingFragmentBorderBoxIterator::new(requested_node.opaque());
sequential::iterate_through_flow_tree_fragment_border_boxes(layout_root, &mut iterator);
iterator.rects
}
struct FragmentLocatingFragmentIterator {
node_address: OpaqueNode,
client_rect: Rect<i32>,
}
impl FragmentLocatingFragmentIterator {
fn new(node_address: OpaqueNode) -> FragmentLocatingFragmentIterator {
FragmentLocatingFragmentIterator {
node_address: node_address,
client_rect: Rect::zero()
}
}
}
struct UnioningFragmentScrollAreaIterator {
node_address: OpaqueNode,
union_rect: Rect<i32>,
origin_rect: Rect<i32>,
level: Option<i32>,
is_child: bool,
overflow_direction: OverflowDirection
}
impl UnioningFragmentScrollAreaIterator {
fn new(node_address: OpaqueNode) -> UnioningFragmentScrollAreaIterator {
UnioningFragmentScrollAreaIterator {
node_address: node_address,
union_rect: Rect::zero(),
origin_rect: Rect::zero(),
level: None,
is_child: false,
overflow_direction: OverflowDirection::RightAndDown
}
}
}
struct NodeOffsetBoxInfo {
offset: Point2D<Au>,
rectangle: Rect<Au>,
}
struct ParentBorderBoxInfo {
node_address: OpaqueNode,
origin: Point2D<Au>,
}
struct ParentOffsetBorderBoxIterator {
node_address: OpaqueNode,
has_processed_node: bool,
node_offset_box: Option<NodeOffsetBoxInfo>,
parent_nodes: Vec<Option<ParentBorderBoxInfo>>,
}
impl ParentOffsetBorderBoxIterator {
fn new(node_address: OpaqueNode) -> ParentOffsetBorderBoxIterator {
ParentOffsetBorderBoxIterator {
node_address: node_address,
has_processed_node: false,
node_offset_box: None,
parent_nodes: Vec::new(),
}
}
}
impl FragmentBorderBoxIterator for FragmentLocatingFragmentIterator {
fn process(&mut self, fragment: &Fragment, _: i32, border_box: &Rect<Au>) {
let style_structs::Border {
border_top_width: top_width,
border_right_width: right_width,
border_bottom_width: bottom_width,
border_left_width: left_width,
..
} = *fragment.style.get_border();
self.client_rect.origin.y = top_width.to_px();
self.client_rect.origin.x = left_width.to_px();
self.client_rect.size.width = (border_box.size.width - left_width - right_width).to_px();
self.client_rect.size.height = (border_box.size.height - top_width - bottom_width).to_px();
}
fn should_process(&mut self, fragment: &Fragment) -> bool {
fragment.node == self.node_address
}
}
// https://drafts.csswg.org/cssom-view/#scrolling-area
impl FragmentBorderBoxIterator for UnioningFragmentScrollAreaIterator {
fn process(&mut self, fragment: &Fragment, level: i32, border_box: &Rect<Au>) {
// In cases in which smaller child elements contain less padding than the parent
// the a union of the two elements padding rectangles could result in an unwanted
// increase in size. To work around this, we store the original elements padding
// rectangle as `origin_rect` and the union of all child elements padding and
// margin rectangles as `union_rect`.
let style_structs::Border {
border_top_width: top_border,
border_right_width: right_border,
border_bottom_width: bottom_border,
border_left_width: left_border,
..
} = *fragment.style.get_border();
let right_padding = (border_box.size.width - right_border - left_border).to_px();
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(_) => {
let padding = Rect::new(Point2D::new(left_padding, top_padding),
Size2D::new(right_padding, bottom_padding));
let top_margin = fragment.margin.top(fragment.style.writing_mode).to_px();
let left_margin = fragment.margin.left(fragment.style.writing_mode).to_px();
let bottom_margin = fragment.margin.bottom(fragment.style.writing_mode).to_px();
let right_margin = fragment.margin.right(fragment.style.writing_mode).to_px();
let margin = Rect::new(Point2D::new(left_margin, top_margin),
Size2D::new(right_margin, bottom_margin));
self.union_rect = self.union_rect.union(&margin).union(&padding);
}
None => {
self.level = Some(level);
self.is_child = true;
self.overflow_direction = overflow_direction(&fragment.style.writing_mode);
self.origin_rect = Rect::new(Point2D::new(left_padding, top_padding),
Size2D::new(right_padding, bottom_padding));
},
};
}
fn should_process(&mut self, fragment: &Fragment) -> bool {
fragment.contains_node(self.node_address) || self.is_child
}
}
// https://drafts.csswg.org/cssom-view/#extensions-to-the-htmlelement-interface
impl FragmentBorderBoxIterator for ParentOffsetBorderBoxIterator {
fn process(&mut self, fragment: &Fragment, level: i32, border_box: &Rect<Au>) {
if self.node_offset_box.is_none() {
// We haven't found the node yet, so we're still looking
// for its parent. Remove all nodes at this level or
// higher, as they can't be parents of this node.
self.parent_nodes.truncate(level as usize);
assert_eq!(self.parent_nodes.len(), level as usize,
"Skipped at least one level in the flow tree!");
}
if !fragment.is_primary_fragment() {
// This fragment doesn't correspond to anything worth
// taking measurements from.
if self.node_offset_box.is_none() {
// If this is the only fragment in the flow, we need to
// do this to avoid failing the above assertion.
self.parent_nodes.push(None);
}
return;
}
if fragment.node == self.node_address {
// Found the fragment in the flow tree that matches the
// DOM node being looked for.
assert!(self.node_offset_box.is_none(),
"Node was being treated as inline, but it has an associated fragment!");
self.has_processed_node = true;
self.node_offset_box = Some(NodeOffsetBoxInfo {
offset: border_box.origin,
rectangle: *border_box,
});
// offsetParent returns null if the node is fixed.
if fragment.style.get_box().position == computed_values::position::T::fixed {
self.parent_nodes.clear();
}
} else if let Some(node) = fragment.inline_context.as_ref().and_then(|inline_context| {
inline_context.nodes.iter().find(|node| node.address == self.node_address)
}) {
// TODO: Handle cases where the `offsetParent` is an inline
// element. This will likely be impossible until
// https://github.com/servo/servo/issues/13982 is fixed.
// Found a fragment in the flow tree whose inline context
// contains the DOM node we're looking for, i.e. the node
// is inline and contains this fragment.
match self.node_offset_box {
Some(NodeOffsetBoxInfo { ref mut rectangle, .. }) => {
*rectangle = rectangle.union(border_box);
},
None => {
// https://github.com/servo/servo/issues/13982 will
// cause this assertion to fail sometimes, so it's
// commented out for now.
/*assert!(node.flags.contains(FIRST_FRAGMENT_OF_ELEMENT),
"First fragment of inline node found wasn't its first fragment!");*/
self.node_offset_box = Some(NodeOffsetBoxInfo {
offset: border_box.origin,
rectangle: *border_box,
});
},
}
if node.flags.contains(LAST_FRAGMENT_OF_ELEMENT) {
self.has_processed_node = true;
}
} else if self.node_offset_box.is_none() {
// TODO(gw): Is there a less fragile way of checking whether this
// fragment is the body element, rather than just checking that
// it's at level 1 (below the root node)?
let is_body_element = level == 1;
let is_valid_parent = match (is_body_element,
fragment.style.get_box().position,
&fragment.specific) {
// Spec says it's valid if any of these are true:
// 1) Is the body element
// 2) Is static position *and* is a table or table cell
// 3) Is not static position
(true, _, _) |
(false, computed_values::position::T::static_, &SpecificFragmentInfo::Table) |
(false, computed_values::position::T::static_, &SpecificFragmentInfo::TableCell) |
(false, computed_values::position::T::absolute, _) |
(false, computed_values::position::T::relative, _) |
(false, computed_values::position::T::fixed, _) => true,
// Otherwise, it's not a valid parent
(false, computed_values::position::T::static_, _) => false,
};
let parent_info = if is_valid_parent {
let border_width = fragment.border_width().to_physical(fragment.style.writing_mode);
Some(ParentBorderBoxInfo {
node_address: fragment.node,
origin: border_box.origin + Point2D::new(border_width.left, border_width.top),
})
} else {
None
};
self.parent_nodes.push(parent_info);
}
}
fn should_process(&mut self, _: &Fragment) -> bool {
!self.has_processed_node
}
}
pub fn process_node_geometry_request<N: LayoutNode>(requested_node: N, layout_root: &mut Flow)
-> Rect<i32> {
let mut iterator = FragmentLocatingFragmentIterator::new(requested_node.opaque());
sequential::iterate_through_flow_tree_fragment_border_boxes(layout_root, &mut iterator);
iterator.client_rect
}
pub fn process_node_scroll_root_id_request<N: LayoutNode>(id: PipelineId,
requested_node: N)
-> ClipId {
let layout_node = requested_node.to_threadsafe();
layout_node.generate_scroll_root_id(id)
}
pub fn process_node_scroll_area_request< N: LayoutNode>(requested_node: N, layout_root: &mut Flow)
-> Rect<i32> {
let mut iterator = UnioningFragmentScrollAreaIterator::new(requested_node.opaque());
sequential::iterate_through_flow_tree_fragment_border_boxes(layout_root, &mut iterator);
match iterator.overflow_direction {
OverflowDirection::RightAndDown => {
let right = max(iterator.union_rect.size.width, iterator.origin_rect.size.width);
let bottom = max(iterator.union_rect.size.height, iterator.origin_rect.size.height);
Rect::new(iterator.origin_rect.origin, Size2D::new(right, bottom))
},
OverflowDirection::LeftAndDown => {
let bottom = max(iterator.union_rect.size.height, iterator.origin_rect.size.height);
let left = max(iterator.union_rect.origin.x, iterator.origin_rect.origin.x);
Rect::new(Point2D::new(left, iterator.origin_rect.origin.y),
Size2D::new(iterator.origin_rect.size.width, bottom))
},
OverflowDirection::LeftAndUp => {
let top = min(iterator.union_rect.origin.y, iterator.origin_rect.origin.y);
let left = min(iterator.union_rect.origin.x, iterator.origin_rect.origin.x);
Rect::new(Point2D::new(left, top), iterator.origin_rect.size)
},
OverflowDirection::RightAndUp => {
let top = min(iterator.union_rect.origin.y, iterator.origin_rect.origin.y);
let right = max(iterator.union_rect.size.width, iterator.origin_rect.size.width);
Rect::new(Point2D::new(iterator.origin_rect.origin.x, top),
Size2D::new(right, iterator.origin_rect.size.height))
}
}
}
/// Return the resolved value of property for a given (pseudo)element.
/// https://drafts.csswg.org/cssom/#resolved-value
pub fn process_resolved_style_request<'a, N>(context: &LayoutContext,
node: N,
pseudo: &Option<PseudoElement>,
property: &PropertyId,
layout_root: &mut Flow) -> String
where N: LayoutNode,
{
use style::traversal::resolve_style;
let element = node.as_element().unwrap();
// We call process_resolved_style_request after performing a whole-document
// traversal, so in the common case, the element is styled.
if element.get_data().is_some() {
return process_resolved_style_request_internal(node, pseudo, property, layout_root);
}
// However, the element may be in a display:none subtree. The style system
// has a mechanism to give us that within a defined scope (after which point
// it's cleared to maintained style system invariants).
let mut tlc = ThreadLocalStyleContext::new(&context.style_context);
let mut context = StyleContext {
shared: &context.style_context,
thread_local: &mut tlc,
};
let mut result = None;
let ensure = |el: N::ConcreteElement| el.as_node().initialize_data();
let clear = |el: N::ConcreteElement| el.as_node().clear_data();
resolve_style(&mut context, element, &ensure, &clear, |_: &_| {
let s = process_resolved_style_request_internal(node, pseudo, property, layout_root);
result = Some(s);
});
result.unwrap()
}
/// The primary resolution logic, which assumes that the element is styled.
fn process_resolved_style_request_internal<'a, N>(requested_node: N,
pseudo: &Option<PseudoElement>,
property: &PropertyId,
layout_root: &mut Flow) -> String
where N: LayoutNode,
{
let layout_el = requested_node.to_threadsafe().as_element().unwrap();
let layout_el = match *pseudo {
Some(PseudoElement::Before) => layout_el.get_before_pseudo(),
Some(PseudoElement::After) => layout_el.get_after_pseudo(),
Some(PseudoElement::DetailsSummary) |
Some(PseudoElement::DetailsContent) |
Some(PseudoElement::Selection) => None,
_ => Some(layout_el)
};
let layout_el = match layout_el {
None => {
// The pseudo doesn't exist, return nothing. Chrome seems to query
// the element itself in this case, Firefox uses the resolved value.
// https://www.w3.org/Bugs/Public/show_bug.cgi?id=29006
return String::new();
}
Some(layout_el) => layout_el
};
let style = &*layout_el.resolved_style();
let longhand_id = match *property {
PropertyId::Longhand(id) => id,
// Firefox returns blank strings for the computed value of shorthands,
// so this should be web-compatible.
PropertyId::Shorthand(_) => return String::new(),
PropertyId::Custom(ref name) => {
return style.computed_value_to_string(PropertyDeclarationId::Custom(name))
}
};
let positioned = match style.get_box().position {
position::computed_value::T::relative |
/*position::computed_value::T::sticky |*/
position::computed_value::T::fixed |
position::computed_value::T::absolute => true,
_ => false
};
//TODO: determine whether requested property applies to the element.
// eg. width does not apply to non-replaced inline elements.
// Existing browsers disagree about when left/top/right/bottom apply
// (Chrome seems to think they never apply and always returns resolved values).
// There are probably other quirks.
let applies = true;
fn used_value_for_position_property<N: LayoutNode>(
layout_el: <N::ConcreteThreadSafeLayoutNode as ThreadSafeLayoutNode>::ConcreteThreadSafeLayoutElement,
layout_root: &mut Flow,
requested_node: N,
longhand_id: LonghandId) -> String {
let maybe_data = layout_el.borrow_layout_data();
let position = maybe_data.map_or(Point2D::zero(), |data| {
match (*data).flow_construction_result {
ConstructionResult::Flow(ref flow_ref, _) =>
flow::base(flow_ref.deref()).stacking_relative_position,
// TODO(dzbarsky) search parents until we find node with a flow ref.
// https://github.com/servo/servo/issues/8307
_ => Point2D::zero()
}
});
let property = match longhand_id {
LonghandId::Bottom => PositionProperty::Bottom,
LonghandId::Top => PositionProperty::Top,
LonghandId::Left => PositionProperty::Left,
LonghandId::Right => PositionProperty::Right,
LonghandId::Width => PositionProperty::Width,
LonghandId::Height => PositionProperty::Height,
_ => unreachable!()
};
let mut iterator =
PositionRetrievingFragmentBorderBoxIterator::new(requested_node.opaque(),
property,
position);
sequential::iterate_through_flow_tree_fragment_border_boxes(layout_root,
&mut iterator);
iterator.result.map(|r| r.to_css_string()).unwrap_or(String::new())
}
// TODO: we will return neither the computed nor used value for margin and padding.
match longhand_id {
LonghandId::MarginBottom | LonghandId::MarginTop |
LonghandId::MarginLeft | LonghandId::MarginRight |
LonghandId::PaddingBottom | LonghandId::PaddingTop |
LonghandId::PaddingLeft | LonghandId::PaddingRight
if applies && style.get_box().display != display::computed_value::T::none => {
let (margin_padding, side) = match longhand_id {
LonghandId::MarginBottom => (MarginPadding::Margin, Side::Bottom),
LonghandId::MarginTop => (MarginPadding::Margin, Side::Top),
LonghandId::MarginLeft => (MarginPadding::Margin, Side::Left),
LonghandId::MarginRight => (MarginPadding::Margin, Side::Right),
LonghandId::PaddingBottom => (MarginPadding::Padding, Side::Bottom),
LonghandId::PaddingTop => (MarginPadding::Padding, Side::Top),
LonghandId::PaddingLeft => (MarginPadding::Padding, Side::Left),
LonghandId::PaddingRight => (MarginPadding::Padding, Side::Right),
_ => unreachable!()
};
let mut iterator =
MarginRetrievingFragmentBorderBoxIterator::new(requested_node.opaque(),
side,
margin_padding,
style.writing_mode);
sequential::iterate_through_flow_tree_fragment_border_boxes(layout_root,
&mut iterator);
iterator.result.map(|r| r.to_css_string()).unwrap_or(String::new())
},
LonghandId::Bottom | LonghandId::Top | LonghandId::Right | LonghandId::Left
if applies && positioned && style.get_box().display !=
display::computed_value::T::none => {
used_value_for_position_property(layout_el, layout_root, requested_node, longhand_id)
}
LonghandId::Width | LonghandId::Height
if applies && style.get_box().display !=
display::computed_value::T::none => {
used_value_for_position_property(layout_el, layout_root, requested_node, longhand_id)
}
// FIXME: implement used value computation for line-height
_ => {
style.computed_value_to_string(PropertyDeclarationId::Longhand(longhand_id))
}
}
}
pub fn process_offset_parent_query<N: LayoutNode>(requested_node: N, layout_root: &mut Flow)
-> OffsetParentResponse {
let mut iterator = ParentOffsetBorderBoxIterator::new(requested_node.opaque());
sequential::iterate_through_flow_tree_fragment_border_boxes(layout_root, &mut iterator);
let node_offset_box = iterator.node_offset_box;
let parent_info = iterator.parent_nodes.into_iter().rev().filter_map(|info| info).next();
match (node_offset_box, parent_info) {
(Some(node_offset_box), Some(parent_info)) => {
let origin = node_offset_box.offset - parent_info.origin;
let size = node_offset_box.rectangle.size;
OffsetParentResponse {
node_address: Some(parent_info.node_address.to_untrusted_node_address()),
rect: Rect::new(origin, size),
}
}
_ => {
OffsetParentResponse::empty()
}
}
}
pub fn process_node_overflow_request<N: LayoutNode>(requested_node: N) -> NodeOverflowResponse {
let layout_node = requested_node.to_threadsafe();
let style = &*layout_node.as_element().unwrap().resolved_style();
let style_box = style.get_box();
NodeOverflowResponse(Some((Point2D::new(style_box.overflow_x, style_box.overflow_y))))
}
pub fn process_margin_style_query<N: LayoutNode>(requested_node: N)
-> MarginStyleResponse {
let layout_node = requested_node.to_threadsafe();
let style = &*layout_node.as_element().unwrap().resolved_style();
let margin = style.get_margin();
MarginStyleResponse {
top: margin.margin_top,
right: margin.margin_right,
bottom: margin.margin_bottom,
left: margin.margin_left,
}
}