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Auto merge of #11205 - pcwalton:avoid-needless-animation-state-changes, r=jdm

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script: Avoid needless `ChangeRunningAnimationsState` messages during typical `requestAnimationFrame()` animations.

This skips useless message traffic when `requestAnimationFrame()` is
called during an animation frame callback. It reduces CPU usage of the
following snippet by 49%:

    <script>
        function foo() {
            requestAnimationFrame(foo);
        }
    </script>
    <button onclick="foo()">Start rAF</button>

Partially addresses #9844.

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This commit is contained in:
bors-servo 2016-05-17 17:24:46 -07:00
commit e5c3bb8977
1 changed files with 22 additions and 4 deletions
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26
components/script/dom/document.rs
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@ -201,6 +201,11 @@ pub struct Document {
/// List of animation frame callbacks
#[ignore_heap_size_of = "closures are hard"]
animation_frame_list: DOMRefCell<BTreeMap<u32, Box<FnBox(f64)>>>,
/// Whether we're in the process of running animation callbacks.
///
/// Tracking this is not necessary for correctness. Instead, it is an optimization to avoid
/// sending needless `ChangeRunningAnimationsState` messages to the compositor.
running_animation_callbacks: Cell<bool>,
/// Tracks all outstanding loads related to this document.
loader: DOMRefCell<DocumentLoader>,
/// The current active HTML parser, to allow resuming after interruptions.
@ -1281,11 +1286,20 @@ impl Document {
self.animation_frame_ident.set(ident);
self.animation_frame_list.borrow_mut().insert(ident, callback);
// No need to send a `ChangeRunningAnimationsState` if we're running animation callbacks:
// we're guaranteed to already be in the "animation callbacks present" state.
//
// This reduces CPU usage by avoiding needless thread wakeups in the common case of
// repeated rAF.
//
// TODO: Should tick animation only when document is visible
let ConstellationChan(ref chan) = *self.window.constellation_chan();
let event = ConstellationMsg::ChangeRunningAnimationsState(self.window.pipeline(),
AnimationState::AnimationCallbacksPresent);
chan.send(event).unwrap();
if !self.running_animation_callbacks.get() {
let ConstellationChan(ref chan) = *self.window.constellation_chan();
let event = ConstellationMsg::ChangeRunningAnimationsState(
self.window.pipeline(),
AnimationState::AnimationCallbacksPresent);
chan.send(event).unwrap();
}
ident
}
@ -1305,6 +1319,7 @@ impl Document {
pub fn run_the_animation_frame_callbacks(&self) {
let animation_frame_list =
mem::replace(&mut *self.animation_frame_list.borrow_mut(), BTreeMap::new());
self.running_animation_callbacks.set(true);
let performance = self.window.Performance();
let performance = performance.r();
let timing = performance.Now();
@ -1324,6 +1339,8 @@ impl Document {
chan.send(event).unwrap();
}
self.running_animation_callbacks.set(false);
self.window.reflow(ReflowGoal::ForDisplay,
ReflowQueryType::NoQuery,
ReflowReason::RequestAnimationFrame);
@ -1676,6 +1693,7 @@ impl Document {
scripting_enabled: Cell::new(browsing_context.is_some()),
animation_frame_ident: Cell::new(0),
animation_frame_list: DOMRefCell::new(BTreeMap::new()),
running_animation_callbacks: Cell::new(false),
loader: DOMRefCell::new(doc_loader),
current_parser: Default::default(),
reflow_timeout: Cell::new(None),