Use a restyle for animation ticks

This change corrects synchronization issues with animations, by
reworking the animation processing model to do a quick restyle and
incremental layout when ticking animations.

While this change adds overhead to animation ticks, the idea is that
this will be the fallback when synchronous behavior is required to
fulfill specification requirements. In the optimistic case, many
animations could be updated and applied off-the-main-thread and then
resynchronized when style information is queried by script.

Fixes #13865.

1 files changed, 44 insertions, 17 deletions

diff --git a/components/script/script_thread.rs b/components/script/script_thread.rs
index 165e526fa76..5a99d800799 100644
--- a/components/script/script_thread.rs
+++ b/components/script/script_thread.rs
@@ -136,12 +136,12 @@ use script_traits::CompositorEvent::{
     WheelEvent,
 };
 use script_traits::{
-    CompositorEvent, ConstellationControlMsg, DiscardBrowsingContext, DocumentActivity,
-    EventResult, HistoryEntryReplacement, InitialScriptState, JsEvalResult, LayoutMsg, LoadData,
-    LoadOrigin, MediaSessionActionType, MouseButton, MouseEventType, NewLayoutInfo, Painter,
-    ProgressiveWebMetricType, ScriptMsg, ScriptThreadFactory, ScriptToConstellationChan,
-    StructuredSerializedData, TimerSchedulerMsg, TouchEventType, TouchId,
-    TransitionOrAnimationEventType, UntrustedNodeAddress, UpdatePipelineIdReason,
+    AnimationTickType, CompositorEvent, ConstellationControlMsg, DiscardBrowsingContext,
+    DocumentActivity, EventResult, HistoryEntryReplacement, InitialScriptState, JsEvalResult,
+    LayoutMsg, LoadData, LoadOrigin, MediaSessionActionType, MouseButton, MouseEventType,
+    NewLayoutInfo, Painter, ProgressiveWebMetricType, ScriptMsg, ScriptThreadFactory,
+    ScriptToConstellationChan, StructuredSerializedData, TimerSchedulerMsg, TouchEventType,
+    TouchId, TransitionOrAnimationEventType, UntrustedNodeAddress, UpdatePipelineIdReason,
     WebrenderIpcSender, WheelDelta, WindowSizeData, WindowSizeType,
 };
 use servo_atoms::Atom;
@@ -1497,7 +1497,7 @@ impl ScriptThread {
                         self.handle_set_scroll_state(id, &scroll_state);
                     })
                 },
-                FromConstellation(ConstellationControlMsg::TickAllAnimations(pipeline_id)) => {
+                FromConstellation(ConstellationControlMsg::TickAllAnimations(pipeline_id, _)) => {
                     // step 7.8
                     if !animation_ticks.contains(&pipeline_id) {
                         animation_ticks.insert(pipeline_id);
@@ -1703,7 +1703,7 @@ impl ScriptThread {
                 RemoveHistoryStates(id, ..) => Some(id),
                 FocusIFrame(id, ..) => Some(id),
                 WebDriverScriptCommand(id, ..) => Some(id),
-                TickAllAnimations(id) => Some(id),
+                TickAllAnimations(id, ..) => Some(id),
                 TransitionOrAnimationEvent { .. } => None,
                 WebFontLoaded(id) => Some(id),
                 DispatchIFrameLoadEvent {
@@ -1902,8 +1902,8 @@ impl ScriptThread {
             ConstellationControlMsg::WebDriverScriptCommand(pipeline_id, msg) => {
                 self.handle_webdriver_msg(pipeline_id, msg)
             },
-            ConstellationControlMsg::TickAllAnimations(pipeline_id) => {
-                self.handle_tick_all_animations(pipeline_id)
+            ConstellationControlMsg::TickAllAnimations(pipeline_id, tick_type) => {
+                self.handle_tick_all_animations(pipeline_id, tick_type)
             },
             ConstellationControlMsg::TransitionOrAnimationEvent {
                 pipeline_id,
@@ -2914,13 +2914,45 @@ impl ScriptThread {
         debug!("Exited script thread.");
     }
 
+    fn restyle_animating_nodes(&self, id: &PipelineId) -> bool {
+        match self.animating_nodes.borrow().get(id) {
+            Some(nodes) => {
+                for node in nodes.iter() {
+                    node.dirty(NodeDamage::NodeStyleDamaged);
+                }
+                true
+            },
+            None => false,
+        }
+    }
+
+    pub fn restyle_animating_nodes_for_advancing_clock(id: &PipelineId) {
+        SCRIPT_THREAD_ROOT.with(|root| {
+            let script_thread = unsafe { &*root.get().unwrap() };
+            script_thread.restyle_animating_nodes(id);
+        });
+    }
+
     /// Handles when layout thread finishes all animation in one tick
-    fn handle_tick_all_animations(&self, id: PipelineId) {
+    fn handle_tick_all_animations(&self, id: PipelineId, tick_type: AnimationTickType) {
         let document = match self.documents.borrow().find_document(id) {
             Some(document) => document,
             None => return warn!("Message sent to closed pipeline {}.", id),
         };
-        document.run_the_animation_frame_callbacks();
+        if tick_type.contains(AnimationTickType::REQUEST_ANIMATION_FRAME) {
+            document.run_the_animation_frame_callbacks();
+        }
+        if tick_type.contains(AnimationTickType::CSS_ANIMATIONS_AND_TRANSITIONS) {
+            if !self.restyle_animating_nodes(&id) {
+                return;
+            }
+
+            document.window().force_reflow(
+                ReflowGoal::TickAnimations,
+                ReflowReason::TickAnimations,
+                None,
+            );
+        }
     }
 
     /// Handles firing of transition-related events.
@@ -2969,11 +3001,6 @@ impl ScriptThread {
             }
         }
 
-        // Not quite the right thing - see #13865.
-        if event_type.finalizes_transition_or_animation() {
-            node.dirty(NodeDamage::NodeStyleDamaged);
-        }
-
         let event_atom = match event_type {
             TransitionOrAnimationEventType::AnimationEnd => atom!("animationend"),
             TransitionOrAnimationEventType::TransitionCancel => atom!("transitioncancel"),