Implement animationiteration event

This event is triggered when an animation iterates. This change also
moves iteration out of style calculation to an "update animations" which
is the next part of having animation event handling match the HTML spec.

components/script/animations.rs

@@ -35,6 +35,30 @@ impl Animations {
         }
     }
 
+    pub(crate) fn update_for_new_timeline_value(
+        &mut self,
+        window: &Window,
+        now: f64,
+    ) -> AnimationsUpdate {
+        let mut update = AnimationsUpdate::new(window.pipeline_id());
+        let mut sets = self.sets.write();
+
+        for set in sets.values_mut() {
+            // When necessary, iterate our running animations to the next iteration.
+            for animation in set.animations.iter_mut() {
+                if animation.iterate_if_necessary(now) {
+                    update.add_event(
+                        animation.node,
+                        animation.name.to_string(),
+                        TransitionOrAnimationEventType::AnimationIteration,
+                        animation.active_duration(),
+                    );
+                }
+            }
+        }
+        update
+    }
+
     /// Processes any new animations that were discovered after reflow. Collect messages
     /// that trigger events for any animations that changed state.
     /// TODO(mrobinson): The specification dictates that this should happen before reflow.
@@ -255,6 +279,9 @@ pub enum TransitionOrAnimationEventType {
     TransitionCancel,
     /// "The animationend event occurs when the animation finishes"
     AnimationEnd,
+    /// "The animationiteration event occurs at the end of each iteration of an
+    /// animation, except when an animationend event would fire at the same time."
+    AnimationIteration,
 }
 
 impl TransitionOrAnimationEventType {
@@ -263,15 +290,15 @@ impl TransitionOrAnimationEventType {
     pub fn finalizes_transition_or_animation(&self) -> bool {
         match *self {
             Self::TransitionEnd | Self::TransitionCancel | Self::AnimationEnd => true,
-            Self::TransitionRun => false,
+            Self::TransitionRun | Self::AnimationIteration => false,
         }
     }
 
     /// Whether or not this event is a transition-related event.
     pub fn is_transition_event(&self) -> bool {
         match *self {
             Self::TransitionRun | Self::TransitionEnd | Self::TransitionCancel => true,
-            Self::AnimationEnd => false,
+            Self::AnimationEnd | Self::AnimationIteration => false,
         }
     }
 }

components/script/dom/document.rs

@@ -3750,12 +3750,26 @@ impl Document {
             .collect()
     }
 
-    pub(crate) fn advance_animation_timeline_for_testing(&self, delta: f64) {
+    pub(crate) fn advance_animation_timeline_for_testing(&self, delta: f64) -> AnimationsUpdate {
         self.animation_timeline.borrow_mut().advance_specific(delta);
+        let current_timeline_value = self.current_animation_timeline_value();
+        self.animations
+            .borrow_mut()
+            .update_for_new_timeline_value(&self.window, current_timeline_value)
     }
 
-    pub(crate) fn update_animation_timeline(&self) {
-        self.animation_timeline.borrow_mut().update();
+    pub(crate) fn update_animation_timeline(&self) -> AnimationsUpdate {
+        // Only update the time if it isn't being managed by a test.
+        if !pref!(layout.animations.test.enabled) {
+            self.animation_timeline.borrow_mut().update();
+        }
+
+        // We still want to update the animations, because our timeline
+        // value might have been advanced previously via the TestBinding.
+        let current_timeline_value = self.current_animation_timeline_value();
+        self.animations
+            .borrow_mut()
+            .update_for_new_timeline_value(&self.window, current_timeline_value)
     }
 
     pub(crate) fn current_animation_timeline_value(&self) -> f64 {
@@ -3766,7 +3780,7 @@ impl Document {
         self.animations.borrow()
     }
 
-    pub(crate) fn update_animations(&self) -> AnimationsUpdate {
+    pub(crate) fn update_animations_post_reflow(&self) -> AnimationsUpdate {
         self.animations
             .borrow_mut()
             .do_post_reflow_update(&self.window, self.current_animation_timeline_value())

components/script/dom/macros.rs

@@ -443,6 +443,7 @@ macro_rules! global_event_handlers(
     (NoOnload) => (
         event_handler!(abort, GetOnabort, SetOnabort);
         event_handler!(animationend, GetOnanimationend, SetOnanimationend);
+        event_handler!(animationiteration, GetOnanimationiteration, SetOnanimationiteration);
         event_handler!(cancel, GetOncancel, SetOncancel);
         event_handler!(canplay, GetOncanplay, SetOncanplay);
         event_handler!(canplaythrough, GetOncanplaythrough, SetOncanplaythrough);

components/script/dom/webidls/EventHandler.webidl

@@ -93,6 +93,7 @@ interface mixin GlobalEventHandlers {
 // https://drafts.csswg.org/css-animations/#interface-globaleventhandlers-idl
 partial interface mixin GlobalEventHandlers {
            attribute EventHandler onanimationend;
+           attribute EventHandler onanimationiteration;
 };
 
 // https://drafts.csswg.org/css-transitions/#interface-globaleventhandlers-idl

components/script/dom/window.rs

@@ -1578,10 +1578,15 @@ impl Window {
 
     /// Prepares to tick animations and then does a reflow which also advances the
     /// layout animation clock.
-    pub fn advance_animation_clock(&self, delta: i32) {
+    #[allow(unsafe_code)]
+    pub fn advance_animation_clock(&self, delta_ms: i32) {
         let pipeline_id = self.upcast::<GlobalScope>().pipeline_id();
-        self.Document()
-            .advance_animation_timeline_for_testing(delta as f64 / 1000.);
+        let update = self
+            .Document()
+            .advance_animation_timeline_for_testing(delta_ms as f64 / 1000.);
+        unsafe {
+            ScriptThread::process_animations_update(update);
+        }
         ScriptThread::handle_tick_all_animations_for_testing(pipeline_id);
     }
 
@@ -1747,7 +1752,7 @@ impl Window {
             }
         }
 
-        let update = document.update_animations();
+        let update = document.update_animations_post_reflow();
         unsafe {
             ScriptThread::process_animations_update(update);
         }

components/script/script_thread.rs

@@ -151,7 +151,6 @@ use script_traits::{
 };
 use servo_atoms::Atom;
 use servo_config::opts;
-use servo_config::pref;
 use servo_url::{ImmutableOrigin, MutableOrigin, ServoUrl};
 use std::borrow::Cow;
 use std::cell::Cell;
@@ -1650,19 +1649,17 @@ impl ScriptThread {
     // TODO(mrobinson): This should also update the current animations to conform to
     // the HTML specification.
     fn update_animations_and_send_events(&self) {
-        for (_, document) in self.documents.borrow().iter() {
-            // Only update the time if it isn't being managed by a test.
-            if !pref!(layout.animations.test.enabled) {
-                document.update_animation_timeline();
-            }
-        }
-
         // We remove the events because handling these events might trigger
         // a reflow which might want to add more events to the queue.
         let events = self.animation_events.replace(Vec::new());
         for event in events.into_iter() {
             self.handle_transition_or_animation_event(&event);
         }
+
+        for (_, document) in self.documents.borrow().iter() {
+            let update = document.update_animation_timeline();
+            unsafe { ScriptThread::process_animations_update(update) };
+        }
     }
 
     fn categorize_msg(&self, msg: &MixedMessage) -> ScriptThreadEventCategory {
@@ -3021,6 +3018,7 @@ impl ScriptThread {
 
         let event_atom = match event.event_type {
             TransitionOrAnimationEventType::AnimationEnd => atom!("animationend"),
+            TransitionOrAnimationEventType::AnimationIteration => atom!("animationiteration"),
             TransitionOrAnimationEventType::TransitionCancel => atom!("transitioncancel"),
             TransitionOrAnimationEventType::TransitionEnd => atom!("transitionend"),
             TransitionOrAnimationEventType::TransitionRun => atom!("transitionrun"),

components/style/animation.rs

@@ -156,12 +156,10 @@ pub enum AnimationState {
 /// have to keep track the current iteration and the max iteration count.
 #[derive(Clone, Debug, MallocSizeOf)]
 pub enum KeyframesIterationState {
-    /// Infinite iterations, so no need to track a state.
-    Infinite,
+    /// Infinite iterations with the current iteration count.
+    Infinite(f64),
     /// Current and max iterations.
-    /// TODO: Everything else in this file uses f64, so perhaps this should
-    /// be as well.
-    Finite(f32, f32),
+    Finite(f64, f64),
 }
 
 /// A CSS Animation
@@ -227,26 +225,26 @@ impl Animation {
 
     /// Given the current time, advances this animation to the next iteration,
     /// updates times, and then toggles the direction if appropriate. Otherwise
-    /// does nothing.
-    pub fn iterate_if_necessary(&mut self, time: f64) {
+    /// does nothing. Returns true if this animation has iterated.
+    pub fn iterate_if_necessary(&mut self, time: f64) -> bool {
         if !self.iteration_over(time) {
-            return;
+            return false;
         }
 
         // Only iterate animations that are currently running.
         if self.state != AnimationState::Running {
-            return;
+            return false;
         }
 
         if let KeyframesIterationState::Finite(ref mut current, max) = self.iteration_state {
-            // If we are already on the final iteration, just exit now.
-            // NB: This prevent us from updating the direction, which might be
-            // needed for the correct handling of animation-fill-mode.
-            if (max - *current) <= 1.0 {
-                return;
+            // If we are already on the final iteration, just exit now. This prevents
+            // us from updating the direction, which might be needed for the correct
+            // handling of animation-fill-mode and also firing animationiteration events
+            // at the end of animations.
+            *current = (*current + 1.).min(max);
+            if *current == max {
+                return false;
             }
-
-            *current += 1.0;
         }
 
         // Update the next iteration direction if applicable.
@@ -262,6 +260,8 @@ impl Animation {
             },
             _ => {},
         }
+
+        true
     }
 
     fn iteration_over(&self, time: f64) -> bool {
@@ -285,8 +285,8 @@ impl Animation {
         // If we have a limited number of iterations and we cannot advance to another
         // iteration, then we have ended.
         return match self.iteration_state {
-            KeyframesIterationState::Finite(current, max) if (max - current) <= 1.0 => true,
-            KeyframesIterationState::Finite(..) | KeyframesIterationState::Infinite => false,
+            KeyframesIterationState::Finite(current, max) => max == current,
+            KeyframesIterationState::Infinite(..) => false,
         };
     }
 
@@ -347,13 +347,11 @@ impl Animation {
     }
 
     /// Calculate the active-duration of this animation according to
-    /// https://drafts.csswg.org/css-animations/#active-duration. active-duration
-    /// is not really meaningful for infinite animations so we just return 0
-    /// here in that case.
+    /// https://drafts.csswg.org/css-animations/#active-duration.
     pub fn active_duration(&self) -> f64 {
         match self.iteration_state {
-            KeyframesIterationState::Finite(_, max) => self.duration * (max as f64),
-            KeyframesIterationState::Infinite => 0.,
+            KeyframesIterationState::Finite(current, _) |
+            KeyframesIterationState::Infinite(current) => self.duration * current,
         }
     }
 
@@ -784,11 +782,6 @@ impl ElementAnimationSet {
         }
 
         maybe_start_animations(element, &context, &new_style, self);
-
-        // When necessary, iterate our running animations to the next iteration.
-        for animation in self.animations.iter_mut() {
-            animation.iterate_if_necessary(context.current_time_for_animations);
-        }
     }
 
     /// Update our transitions given a new style, canceling or starting new animations
@@ -1039,8 +1032,8 @@ pub fn maybe_start_animations<E>(
         let delay = box_style.animation_delay_mod(i).seconds();
         let animation_start = context.current_time_for_animations + delay as f64;
         let iteration_state = match box_style.animation_iteration_count_mod(i) {
-            AnimationIterationCount::Infinite => KeyframesIterationState::Infinite,
-            AnimationIterationCount::Number(n) => KeyframesIterationState::Finite(0.0, n),
+            AnimationIterationCount::Infinite => KeyframesIterationState::Infinite(0.0),
+            AnimationIterationCount::Number(n) => KeyframesIterationState::Finite(0.0, n.into()),
         };
 
         let animation_direction = box_style.animation_direction_mod(i);

tests/wpt/metadata-layout-2020/css/css-animations/animationevent-types.html.ini

@@ -1,8 +1,5 @@
 [animationevent-types.html]
   expected: TIMEOUT
-  [animationiteration event is instanceof AnimationEvent]
-    expected: TIMEOUT
-
   [animationstart event is instanceof AnimationEvent]
     expected: TIMEOUT
 

tests/wpt/metadata-layout-2020/css/css-animations/idlharness.html.ini

@@ -1,7 +1,4 @@
 [idlharness.html]
-  [HTMLElement interface: attribute onanimationiteration]
-    expected: FAIL
-
   [HTMLElement interface: attribute onanimationstart]
     expected: FAIL
 
@@ -20,18 +17,12 @@
   [Window interface: attribute onanimationstart]
     expected: FAIL
 
-  [Window interface: attribute onanimationiteration]
-    expected: FAIL
-
   [Document interface: attribute onanimationcancel]
     expected: FAIL
 
   [CSSKeyframeRule interface: attribute style]
     expected: FAIL
 
-  [Document interface: attribute onanimationiteration]
-    expected: FAIL
-
   [HTMLElement interface: attribute onanimationcancel]
     expected: FAIL
 

tests/wpt/metadata/css/css-animations/animationevent-types.html.ini

@@ -1,9 +1,6 @@
 [animationevent-types.html]
   bug: https://github.com/servo/servo/issues/21564
   expected: TIMEOUT
-  [animationiteration event is instanceof AnimationEvent]
-    expected: TIMEOUT
-
   [animationstart event is instanceof AnimationEvent]
     expected: TIMEOUT
 

tests/wpt/metadata/css/css-animations/idlharness.html.ini

@@ -1,16 +1,10 @@
 [idlharness.html]
-  [Document interface: attribute onanimationiteration]
-    expected: FAIL
-
   [CSSKeyframeRule interface: attribute style]
     expected: FAIL
 
   [Document interface: attribute onanimationstart]
     expected: FAIL
 
-  [HTMLElement interface: attribute onanimationiteration]
-    expected: FAIL
-
   [Window interface: attribute onanimationcancel]
     expected: FAIL
 
@@ -29,9 +23,6 @@
   [HTMLElement interface: attribute onanimationcancel]
     expected: FAIL
 
-  [Window interface: attribute onanimationiteration]
-    expected: FAIL
-
   [CSSKeyframeRule interface: keyframes.cssRules[0\] must inherit property "keyText" with the proper type]
     expected: FAIL