Add animation and transition support for pseudo-elements

This change extends the DocumentAnimationSet to hold animations for
pseudo-elements. Since pseudo-elements in Servo are not in the DOM like
in Gecko, they need to be handled a bit carefully in stylo.  When a
pseudo-element has an animation, recascade the style. Finally, this
change passes the pseudo-element string properly to animation events.

Fixes: #10316

1 files changed, 14 insertions, 2 deletions

diff --git a/components/layout_thread/lib.rs b/components/layout_thread/lib.rs
index 5930e85b08c..07cb7c5a4c8 100644
--- a/components/layout_thread/lib.rs
+++ b/components/layout_thread/lib.rs
@@ -109,7 +109,7 @@ use style::invalidation::element::restyle_hints::RestyleHint;
 use style::logical_geometry::LogicalPoint;
 use style::media_queries::{Device, MediaList, MediaType};
 use style::properties::PropertyId;
-use style::selector_parser::SnapshotMap;
+use style::selector_parser::{PseudoElement, SnapshotMap};
 use style::servo::restyle_damage::ServoRestyleDamage;
 use style::shared_lock::{SharedRwLock, SharedRwLockReadGuard, StylesheetGuards};
 use style::stylesheets::{
@@ -1651,7 +1651,19 @@ impl LayoutThread {
 
         fn traverse_flow(flow: &mut dyn Flow, invalid_nodes: &mut FxHashSet<AnimationSetKey>) {
             flow.mutate_fragments(&mut |fragment| {
-                invalid_nodes.remove(&AnimationSetKey(fragment.node));
+                // Ideally we'd only not cancel ::before and ::after animations if they
+                // were actually in the tree. At this point layout has lost information
+                // about whether or not they exist, but have had their fragments accumulated
+                // together.
+                invalid_nodes.remove(&AnimationSetKey::new_for_non_pseudo(fragment.node));
+                invalid_nodes.remove(&AnimationSetKey::new_for_pseudo(
+                    fragment.node,
+                    PseudoElement::Before,
+                ));
+                invalid_nodes.remove(&AnimationSetKey::new_for_pseudo(
+                    fragment.node,
+                    PseudoElement::After,
+                ));
             });
             for kid in flow.mut_base().children.iter_mut() {
                 traverse_flow(kid, invalid_nodes)