Auto merge of #14367 - mrobinson:scroll-fragment-point, r=pcwalton

Reimplement scrolling to fragments

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #13736, #10753 (github issue number if applicable).

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- [x] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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This reimplemntation of the feature uses ScrollRootIds to scroll
particular scrollable areas of the page.

Fixes #13736.
Fixes #10753.

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components/script_layout_interface/message.rs

@@ -94,6 +94,7 @@ pub enum ReflowQueryType {
     ContentBoxesQuery(TrustedNodeAddress),
     NodeOverflowQuery(TrustedNodeAddress),
     HitTestQuery(Point2D<f32>, Point2D<f32>, bool),
+    NodeScrollRootIdQuery(TrustedNodeAddress),
     NodeGeometryQuery(TrustedNodeAddress),
     NodeScrollGeometryQuery(TrustedNodeAddress),
     ResolvedStyleQuery(TrustedNodeAddress, Option<PseudoElement>, Atom),

components/script_layout_interface/rpc.rs

@@ -5,6 +5,7 @@
 use app_units::Au;
 use euclid::point::Point2D;
 use euclid::rect::Rect;
+use gfx_traits::ScrollRootId;
 use script_traits::UntrustedNodeAddress;
 use style::properties::longhands::{margin_top, margin_right, margin_bottom, margin_left, overflow_x};
 
@@ -27,6 +28,8 @@ pub trait LayoutRPC {
     fn node_overflow(&self) -> NodeOverflowResponse;
     /// Requests the scroll geometry of this node. Used by APIs such as `scrollTop`.
     fn node_scroll_area(&self) -> NodeGeometryResponse;
+    /// Requests the scroll root id of this node. Used by APIs such as `scrollTop`
+    fn node_scroll_root_id(&self) -> NodeScrollRootIdResponse;
     /// Requests the node containing the point of interest
     fn hit_test(&self) -> HitTestResponse;
     /// Query layout for the resolved value of a given CSS property
@@ -48,6 +51,8 @@ pub struct NodeGeometryResponse {
 
 pub struct NodeOverflowResponse(pub Option<Point2D<overflow_x::computed_value::T>>);
 
+pub struct NodeScrollRootIdResponse(pub ScrollRootId);
+
 pub struct HitTestResponse {
     pub node_address: Option<UntrustedNodeAddress>,
 }

components/script_layout_interface/wrapper_traits.rs

@@ -8,7 +8,7 @@ use HTMLCanvasData;
 use LayoutNodeType;
 use OpaqueStyleAndLayoutData;
 use SVGSVGData;
-use gfx_traits::ByteIndex;
+use gfx_traits::{ByteIndex, FragmentType, ScrollRootId};
 use html5ever_atoms::{Namespace, LocalName};
 use msg::constellation_msg::PipelineId;
 use range::Range;
@@ -264,6 +264,20 @@ pub trait ThreadSafeLayoutNode: Clone + Copy + Debug + GetLayoutData + NodeInfo
     fn iframe_pipeline_id(&self) -> PipelineId;
 
     fn get_colspan(&self) -> u32;
+
+    fn fragment_type(&self) -> FragmentType {
+        match self.get_pseudo_element_type() {
+            PseudoElementType::Normal => FragmentType::FragmentBody,
+            PseudoElementType::Before(_) => FragmentType::BeforePseudoContent,
+            PseudoElementType::After(_) => FragmentType::AfterPseudoContent,
+            PseudoElementType::DetailsSummary(_) => FragmentType::FragmentBody,
+            PseudoElementType::DetailsContent(_) => FragmentType::FragmentBody,
+        }
+    }
+
+    fn scroll_root_id(&self) -> ScrollRootId {
+        ScrollRootId::new_of_type(self.opaque().id() as usize, self.fragment_type())
+    }
 }
 
 // This trait is only public so that it can be implemented by the gecko wrapper.