layout: Add a new FragmentTree pass to calculate containing block rectangles (#36629)

When doing any kind of query, up until now, containing block rectangles
were calculated by walking the `FragmentTree` until the node being
queried was found. In order to make possible answering queries without
walking the `FragmentTree`, `Fragment`s need to cache their cumulative
containing block rectangles.

This change adds a new `FragmentTree` pass (during construction) that
takes care of calculating and caching these values. The new cached value
is used during resolved style queries and also scrolling area queries
(with the idea that all queries will eventually use them).

In addition, extra `FragmentTree` walks used for cancelling animations
for elements no longer in the `FragmentTree` are integrated into this
new traversal.

Testing: Covered by existing WPT tests.

Signed-off-by: Martin Robinson <mrobinson@igalia.com>
Co-authored-by: Oriol Brufau <obrufau@igalia.com>

components/layout/fragment_tree/fragment_tree.rs

@@ -13,6 +13,7 @@ use style::dom::OpaqueNode;
 use webrender_api::units;
 
 use super::{ContainingBlockManager, Fragment, Tag};
+use crate::context::LayoutContext;
 use crate::display_list::StackingContext;
 use crate::flow::CanvasBackground;
 use crate::geom::{PhysicalPoint, PhysicalRect};
@@ -44,6 +45,58 @@ pub struct FragmentTree {
 }
 
 impl FragmentTree {
+    pub(crate) fn new(
+        layout_context: &LayoutContext,
+        root_fragments: Vec<Fragment>,
+        scrollable_overflow: PhysicalRect<Au>,
+        initial_containing_block: PhysicalRect<Au>,
+        canvas_background: CanvasBackground,
+        viewport_scroll_sensitivity: AxesScrollSensitivity,
+    ) -> Self {
+        let fragment_tree = Self {
+            root_fragments,
+            scrollable_overflow,
+            initial_containing_block,
+            canvas_background,
+            viewport_scroll_sensitivity,
+        };
+
+        // As part of building the fragment tree, we want to stop animating elements and
+        // pseudo-elements that used to be animating or had animating images attached to
+        // them. Create a set of all elements that used to be animating.
+        let mut animations = layout_context.style_context.animations.sets.write();
+        let mut invalid_animating_nodes: FxHashSet<_> = animations.keys().cloned().collect();
+        let mut image_animations = layout_context.node_image_animation_map.write().to_owned();
+        let mut invalid_image_animating_nodes: FxHashSet<_> = image_animations
+            .keys()
+            .cloned()
+            .map(|node| AnimationSetKey::new(node, None))
+            .collect();
+
+        fragment_tree.find(|fragment, _level, containing_block| {
+            if let Some(tag) = fragment.tag() {
+                invalid_animating_nodes.remove(&AnimationSetKey::new(tag.node, tag.pseudo));
+                invalid_image_animating_nodes.remove(&AnimationSetKey::new(tag.node, tag.pseudo));
+            }
+
+            fragment.set_containing_block(containing_block);
+            None::<()>
+        });
+
+        // Cancel animations for any elements and pseudo-elements that are no longer found
+        // in the fragment tree.
+        for node in &invalid_animating_nodes {
+            if let Some(state) = animations.get_mut(node) {
+                state.cancel_all_animations();
+            }
+        }
+        for node in &invalid_image_animating_nodes {
+            image_animations.remove(&node.node);
+        }
+
+        fragment_tree
+    }
+
     pub(crate) fn build_display_list(
         &self,
         builder: &mut crate::display_list::DisplayListBuilder,
@@ -86,14 +139,6 @@ impl FragmentTree {
             .find_map(|child| child.find(&info, 0, &mut process_func))
     }
 
-    pub fn remove_nodes_in_fragment_tree_from_set(&self, set: &mut FxHashSet<AnimationSetKey>) {
-        self.find(|fragment, _, _| {
-            let tag = fragment.tag()?;
-            set.remove(&AnimationSetKey::new(tag.node, tag.pseudo));
-            None::<()>
-        });
-    }
-
     /// Get the vector of rectangles that surrounds the fragments of the node with the given address.
     /// This function answers the `getClientRects()` query and the union of the rectangles answers
     /// the `getBoundingClientRect()` query.
@@ -173,22 +218,8 @@ impl FragmentTree {
     pub fn get_scrolling_area_for_viewport(&self) -> PhysicalRect<Au> {
         let mut scroll_area = self.initial_containing_block;
         for fragment in self.root_fragments.iter() {
-            scroll_area = fragment
-                .scrolling_area(&self.initial_containing_block)
-                .union(&scroll_area);
+            scroll_area = fragment.scrolling_area().union(&scroll_area);
         }
         scroll_area
     }
-
-    pub fn get_scrolling_area_for_node(&self, requested_node: OpaqueNode) -> PhysicalRect<Au> {
-        let tag_to_find = Tag::new(requested_node);
-        let scroll_area = self.find(|fragment, _, containing_block| {
-            if fragment.tag() == Some(tag_to_find) {
-                Some(fragment.scrolling_area(containing_block))
-            } else {
-                None
-            }
-        });
-        scroll_area.unwrap_or_else(PhysicalRect::<Au>::zero)
-    }
 }