Write animated values into the ComputedValues structures when

animations complete or are interrupted.

This adds a new pair of reader-writer locks. I measured the performance
of style recalculation on Wikipedia and the overhead of the locks was
not measurable.

Closes #7816.

components/layout/animation.rs

@@ -19,11 +19,14 @@ use style::animation::{GetMod, PropertyAnimation};
 use style::properties::ComputedValues;
 
 /// Inserts transitions into the queue of running animations as applicable for the given style
-/// difference. This is called from the layout worker threads.
+/// difference. This is called from the layout worker threads. Returns true if any animations were
+/// kicked off and false otherwise.
 pub fn start_transitions_if_applicable(new_animations_sender: &Mutex<Sender<Animation>>,
                                        node: OpaqueNode,
                                        old_style: &ComputedValues,
-                                       new_style: &mut ComputedValues) {
+                                       new_style: &mut ComputedValues)
+                                       -> bool {
+    let mut had_animations = false;
     for i in 0..new_style.get_animation().transition_property.0.len() {
         // Create any property animations, if applicable.
         let property_animations = PropertyAnimation::from_transition(i, old_style, new_style);
@@ -42,15 +45,20 @@ pub fn start_transitions_if_applicable(new_animations_sender: &Mutex<Sender<Anim
                 start_time: start_time,
                 end_time: start_time +
                     (animation_style.transition_duration.0.get_mod(i).seconds() as f64),
-            }).unwrap()
+            }).unwrap();
+
+            had_animations = true
         }
     }
+
+    had_animations
 }
 
 /// Processes any new animations that were discovered after style recalculation.
-/// Also expire any old animations that have completed.
+/// Also expire any old animations that have completed, inserting them into `expired_animations`.
 pub fn update_animation_state(constellation_chan: &ConstellationChan<ConstellationMsg>,
-                              running_animations: &mut Arc<HashMap<OpaqueNode, Vec<Animation>>>,
+                              running_animations: &mut HashMap<OpaqueNode, Vec<Animation>>,
+                              expired_animations: &mut HashMap<OpaqueNode, Vec<Animation>>,
                               new_animations_receiver: &Receiver<Animation>,
                               pipeline_id: PipelineId) {
     let mut new_running_animations = Vec::new();
@@ -58,9 +66,7 @@ pub fn update_animation_state(constellation_chan: &ConstellationChan<Constellati
         new_running_animations.push(animation)
     }
 
-    let mut running_animations_hash = (**running_animations).clone();
-
-    if running_animations_hash.is_empty() && new_running_animations.is_empty() {
+    if running_animations.is_empty() && new_running_animations.is_empty() {
         // Nothing to do. Return early so we don't flood the compositor with
         // `ChangeRunningAnimationsState` messages.
         return
@@ -69,21 +75,33 @@ pub fn update_animation_state(constellation_chan: &ConstellationChan<Constellati
     // Expire old running animations.
     let now = clock_ticks::precise_time_s();
     let mut keys_to_remove = Vec::new();
-    for (key, running_animations) in &mut running_animations_hash {
-        running_animations.retain(|running_animation| {
-            now < running_animation.end_time
-        });
-        if running_animations.len() == 0 {
+    for (key, running_animations) in running_animations.iter_mut() {
+        let mut animations_still_running = vec![];
+        for running_animation in running_animations.drain(..) {
+            if now < running_animation.end_time {
+                animations_still_running.push(running_animation);
+                continue
+            }
+            match expired_animations.entry(*key) {
+                Entry::Vacant(entry) => {
+                    entry.insert(vec![running_animation]);
+                }
+                Entry::Occupied(mut entry) => entry.get_mut().push(running_animation),
+            }
+        }
+        if animations_still_running.len() == 0 {
             keys_to_remove.push(*key);
+        } else {
+            *running_animations = animations_still_running
         }
     }
     for key in keys_to_remove {
-        running_animations_hash.remove(&key).unwrap();
+        running_animations.remove(&key).unwrap();
     }
 
     // Add new running animations.
     for new_running_animation in new_running_animations {
-        match running_animations_hash.entry(OpaqueNode(new_running_animation.node)) {
+        match running_animations.entry(OpaqueNode(new_running_animation.node)) {
             Entry::Vacant(entry) => {
                 entry.insert(vec![new_running_animation]);
             }
@@ -91,8 +109,6 @@ pub fn update_animation_state(constellation_chan: &ConstellationChan<Constellati
         }
     }
 
-    *running_animations = Arc::new(running_animations_hash);
-
     let animation_state;
     if running_animations.is_empty() {
         animation_state = AnimationState::NoAnimationsPresent;
@@ -112,21 +128,7 @@ pub fn recalc_style_for_animations(flow: &mut Flow,
     flow.mutate_fragments(&mut |fragment| {
         if let Some(ref animations) = animations.get(&OpaqueNode(fragment.node.id())) {
             for animation in *animations {
-                let now = clock_ticks::precise_time_s();
-                let mut progress = (now - animation.start_time) / animation.duration();
-                if progress > 1.0 {
-                    progress = 1.0
-                }
-                if progress <= 0.0 {
-                    continue
-                }
-
-                let mut new_style = fragment.style.clone();
-                animation.property_animation.update(&mut *Arc::make_mut(&mut new_style),
-                                                    progress);
-                damage.insert(incremental::compute_damage(&Some(fragment.style.clone()),
-                                                          &new_style));
-                fragment.style = new_style
+                update_style_for_animation(animation, &mut fragment.style, Some(&mut damage));
             }
         }
     });
@@ -137,3 +139,27 @@ pub fn recalc_style_for_animations(flow: &mut Flow,
         recalc_style_for_animations(kid, animations)
     }
 }
+
+/// Updates a single animation and associated style based on the current time. If `damage` is
+/// provided, inserts the appropriate restyle damage.
+pub fn update_style_for_animation(animation: &Animation,
+                                  style: &mut Arc<ComputedValues>,
+                                  damage: Option<&mut RestyleDamage>) {
+    let now = clock_ticks::precise_time_s();
+    let mut progress = (now - animation.start_time) / animation.duration();
+    if progress > 1.0 {
+        progress = 1.0
+    }
+    if progress <= 0.0 {
+        return
+    }
+
+    let mut new_style = (*style).clone();
+    animation.property_animation.update(&mut *Arc::make_mut(&mut new_style), progress);
+    if let Some(damage) = damage {
+        damage.insert(incremental::compute_damage(&Some((*style).clone()), &new_style));
+    }
+
+    *style = new_style
+}
+

components/layout/context.rs

@@ -25,7 +25,7 @@ use std::collections::HashMap;
 use std::collections::hash_state::DefaultState;
 use std::rc::Rc;
 use std::sync::mpsc::{Sender, channel};
-use std::sync::{Arc, Mutex};
+use std::sync::{Arc, Mutex, RwLock};
 use style::selector_matching::Stylist;
 use url::Url;
 use util::mem::HeapSizeOf;
@@ -120,7 +120,10 @@ pub struct SharedLayoutContext {
     pub visible_rects: Arc<HashMap<LayerId, Rect<Au>, DefaultState<FnvHasher>>>,
 
     /// The animations that are currently running.
-    pub running_animations: Arc<HashMap<OpaqueNode, Vec<Animation>>>,
+    pub running_animations: Arc<RwLock<HashMap<OpaqueNode, Vec<Animation>>>>,
+
+    /// The list of animations that have expired since the last style recalculation.
+    pub expired_animations: Arc<RwLock<HashMap<OpaqueNode, Vec<Animation>>>>,
 
     /// Why is this reflow occurring
     pub goal: ReflowGoal,

components/layout/css/matching.rs

@@ -414,6 +414,10 @@ trait PrivateMatchMethods {
                                    shareable: bool,
                                    animate_properties: bool)
                                    -> RestyleDamage;
+    fn update_animations_for_cascade(&self,
+                                     layout_context: &SharedLayoutContext,
+                                     style: &mut Option<Arc<ComputedValues>>)
+                                     -> bool;
 }
 
 trait PrivateElementMatchMethods {
@@ -435,20 +439,12 @@ impl<'ln> PrivateMatchMethods for ServoLayoutNode<'ln> {
                                    shareable: bool,
                                    animate_properties: bool)
                                    -> RestyleDamage {
-        // Finish any transitions.
+        let mut cacheable = true;
         if animate_properties {
-            if let Some(ref mut style) = *style {
-                let this_opaque = self.opaque();
-                if let Some(ref animations) = layout_context.running_animations.get(&this_opaque) {
-                    for animation in *animations {
-                        animation.property_animation.update(&mut *Arc::make_mut(style), 1.0);
-                    }
-                }
-            }
+            cacheable = !self.update_animations_for_cascade(layout_context, style) && cacheable;
         }
 
         let mut this_style;
-        let cacheable;
         match parent_style {
             Some(ref parent_style) => {
                 let cache_entry = applicable_declarations_cache.find(applicable_declarations);
@@ -461,7 +457,7 @@ impl<'ln> PrivateMatchMethods for ServoLayoutNode<'ln> {
                                                         shareable,
                                                         Some(&***parent_style),
                                                         cached_computed_values);
-                cacheable = is_cacheable;
+                cacheable = cacheable && is_cacheable;
                 this_style = the_style
             }
             None => {
@@ -470,7 +466,7 @@ impl<'ln> PrivateMatchMethods for ServoLayoutNode<'ln> {
                                                         shareable,
                                                         None,
                                                         None);
-                cacheable = is_cacheable;
+                cacheable = cacheable && is_cacheable;
                 this_style = the_style
             }
         };
@@ -479,10 +475,12 @@ impl<'ln> PrivateMatchMethods for ServoLayoutNode<'ln> {
         // it did trigger a transition.
         if animate_properties {
             if let Some(ref style) = *style {
-                animation::start_transitions_if_applicable(new_animations_sender,
-                                                           self.opaque(),
-                                                           &**style,
-                                                           &mut this_style);
+                let animations_started =
+                    animation::start_transitions_if_applicable(new_animations_sender,
+                                                               self.opaque(),
+                                                               &**style,
+                                                               &mut this_style);
+                cacheable = cacheable && !animations_started
             }
         }
 
@@ -500,6 +498,50 @@ impl<'ln> PrivateMatchMethods for ServoLayoutNode<'ln> {
         *style = Some(this_style);
         damage
     }
+
+    fn update_animations_for_cascade(&self,
+                                     layout_context: &SharedLayoutContext,
+                                     style: &mut Option<Arc<ComputedValues>>)
+                                     -> bool {
+        let style = match *style {
+            None => return false,
+            Some(ref mut style) => style,
+        };
+
+        // Finish any expired transitions.
+        let this_opaque = self.opaque();
+        let had_animations_to_expire;
+        {
+            let all_expired_animations = layout_context.expired_animations.read().unwrap();
+            let animations_to_expire = all_expired_animations.get(&this_opaque);
+            had_animations_to_expire = animations_to_expire.is_some();
+            if let Some(ref animations) = animations_to_expire {
+                for animation in *animations {
+                    animation.property_animation.update(&mut *Arc::make_mut(style), 1.0);
+                }
+            }
+        }
+
+        if had_animations_to_expire {
+            layout_context.expired_animations.write().unwrap().remove(&this_opaque);
+        }
+
+        // Merge any running transitions into the current style, and cancel them.
+        let had_running_animations = layout_context.running_animations
+                                                   .read()
+                                                   .unwrap()
+                                                   .get(&this_opaque)
+                                                   .is_some();
+        if had_running_animations {
+            let mut all_running_animations = layout_context.running_animations.write().unwrap();
+            for running_animation in all_running_animations.get(&this_opaque).unwrap() {
+                animation::update_style_for_animation(running_animation, style, None);
+            }
+            all_running_animations.remove(&this_opaque);
+        }
+
+        had_animations_to_expire || had_running_animations
+    }
 }
 
 impl<'ln> PrivateElementMatchMethods for ServoLayoutElement<'ln> {

components/layout/layout_task.rs

@@ -59,7 +59,7 @@ use std::mem::transmute;
 use std::ops::{Deref, DerefMut};
 use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::mpsc::{channel, Sender, Receiver};
-use std::sync::{Arc, Mutex, MutexGuard};
+use std::sync::{Arc, Mutex, MutexGuard, RwLock};
 use style::computed_values::{filter, mix_blend_mode};
 use style::media_queries::{Device, MediaType};
 use style::selector_matching::{Stylist, USER_OR_USER_AGENT_STYLESHEETS};
@@ -194,7 +194,10 @@ pub struct LayoutTask {
     visible_rects: Arc<HashMap<LayerId, Rect<Au>, DefaultState<FnvHasher>>>,
 
     /// The list of currently-running animations.
-    running_animations: Arc<HashMap<OpaqueNode, Vec<Animation>>>,
+    running_animations: Arc<RwLock<HashMap<OpaqueNode, Vec<Animation>>>>,
+
+    /// The list of animations that have expired since the last style recalculation.
+    expired_animations: Arc<RwLock<HashMap<OpaqueNode, Vec<Animation>>>>,
 
     /// A counter for epoch messages
     epoch: Epoch,
@@ -420,7 +423,8 @@ impl LayoutTask {
             outstanding_web_fonts: outstanding_web_fonts_counter,
             root_flow: None,
             visible_rects: Arc::new(HashMap::with_hash_state(Default::default())),
-            running_animations: Arc::new(HashMap::new()),
+            running_animations: Arc::new(RwLock::new(HashMap::new())),
+            expired_animations: Arc::new(RwLock::new(HashMap::new())),
             epoch: Epoch(0),
             viewport_size: Size2D::new(Au(0), Au(0)),
             rw_data: Arc::new(Mutex::new(
@@ -471,6 +475,7 @@ impl LayoutTask {
             new_animations_sender: Mutex::new(self.new_animations_sender.clone()),
             goal: goal,
             running_animations: self.running_animations.clone(),
+            expired_animations: self.expired_animations.clone(),
         }
     }
 
@@ -1137,13 +1142,13 @@ impl LayoutTask {
 
         if let Some(mut root_flow) = self.root_flow.clone() {
             // Perform an abbreviated style recalc that operates without access to the DOM.
-            let animations = &*self.running_animations;
+            let animations = self.running_animations.read().unwrap();
             profile(time::ProfilerCategory::LayoutStyleRecalc,
                     self.profiler_metadata(),
                     self.time_profiler_chan.clone(),
                     || {
                         animation::recalc_style_for_animations(flow_ref::deref_mut(&mut root_flow),
-                                                               animations)
+                                                               &*animations)
                     });
         }
 
@@ -1182,7 +1187,8 @@ impl LayoutTask {
         if let Some(mut root_flow) = self.root_flow.clone() {
             // Kick off animations if any were triggered, expire completed ones.
             animation::update_animation_state(&self.constellation_chan,
-                                              &mut self.running_animations,
+                                              &mut *self.running_animations.write().unwrap(),
+                                              &mut *self.expired_animations.write().unwrap(),
                                               &self.new_animations_receiver,
                                               self.id);
 

components/layout/lib.rs

@@ -5,6 +5,7 @@
 #![feature(box_syntax)]
 #![feature(cell_extras)]
 #![feature(custom_derive)]
+#![feature(drain)]
 #![feature(hashmap_hasher)]
 #![feature(mpsc_select)]
 #![feature(plugin)]