Auto merge of #17398 - glennw:opt-composite, r=jdm

Improve decisions in compositor over when to draw a frame.

This patch fixes a couple of issues in the compositor:

1) Remove the delayed composition code. Previously, this would schedule
   a composite for 12ms in the future. This doesn't really make any sense
   with WR. There's no point in doing a composite unless WR has provided
   a new frame to be drawn. This fixes issues in several benchmarks where
   we were doing multiple composite / renders per rAF, which is a waste
   of CPU time. This *does* make the framerate slower in some cases (such
   as a slow rAF callback) but it's more correct - otherwise we were just
   compositing the same frame multiple times for no real benefit.

2) Inform the window of the current animation state of the compositor.
   Specifically, if an animation (or rAF) is currently active, the
   window system switches to use event polling, and does not block on
   the OS-level event loop. In the case of active animation, we just
   assume that we want to be running as the vsync interval and not
   blocking. This means the compositor thread only sleeps on vsync
   during animation, which reduces OS scheduling and results in much
   smoother animation.

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components/compositing/compositor.rs

@@ -6,7 +6,6 @@ use CompositionPipeline;
 use SendableFrameTree;
 use compositor_thread::{CompositorProxy, CompositorReceiver};
 use compositor_thread::{InitialCompositorState, Msg, RenderListener};
-use delayed_composition::DelayedCompositionTimerProxy;
 use euclid::{Point2D, TypedPoint2D, TypedVector2D, TypedRect, ScaleFactor, TypedSize2D};
 use gfx_traits::Epoch;
 use gleam::gl;
@@ -131,9 +130,6 @@ pub struct IOCompositor<Window: WindowMethods> {
 
     channel_to_self: CompositorProxy,
 
-    /// A handle to the delayed composition timer.
-    delayed_composition_timer: DelayedCompositionTimerProxy,
-
     /// The type of composition to perform
     composite_target: CompositeTarget,
 
@@ -207,7 +203,6 @@ struct ScrollZoomEvent {
 #[derive(PartialEq, Debug)]
 enum CompositionRequest {
     NoCompositingNecessary,
-    DelayedComposite(u64),
     CompositeNow(CompositingReason),
 }
 
@@ -363,7 +358,6 @@ impl<Window: WindowMethods> IOCompositor<Window> {
             scale: ScaleFactor::new(1.0),
             scale_factor: scale_factor,
             channel_to_self: state.sender.clone_compositor_proxy(),
-            delayed_composition_timer: DelayedCompositionTimerProxy::new(state.sender),
             composition_request: CompositionRequest::NoCompositingNecessary,
             touch_handler: TouchHandler::new(),
             pending_scroll_zoom_events: Vec::new(),
@@ -437,8 +431,6 @@ impl<Window: WindowMethods> IOCompositor<Window> {
             let _ = receiver.recv();
         }
 
-        self.delayed_composition_timer.shutdown();
-
         self.shutdown_state = ShutdownState::FinishedShuttingDown;
     }
 
@@ -524,16 +516,6 @@ impl<Window: WindowMethods> IOCompositor<Window> {
                 }
             }
 
-            (Msg::DelayedCompositionTimeout(timestamp), ShutdownState::NotShuttingDown) => {
-                if let CompositionRequest::DelayedComposite(this_timestamp) =
-                    self.composition_request {
-                    if timestamp == this_timestamp {
-                        self.composition_request = CompositionRequest::CompositeNow(
-                            CompositingReason::DelayedCompositeTimeout)
-                    }
-                }
-            }
-
             (Msg::Recomposite(reason), ShutdownState::NotShuttingDown) => {
                 self.composition_request = CompositionRequest::CompositeNow(reason)
             }
@@ -753,18 +735,6 @@ impl<Window: WindowMethods> IOCompositor<Window> {
         }
     }
 
-    fn schedule_delayed_composite_if_necessary(&mut self) {
-        match self.composition_request {
-            CompositionRequest::CompositeNow(_) => return,
-            CompositionRequest::DelayedComposite(_) |
-            CompositionRequest::NoCompositingNecessary => {}
-        }
-
-        let timestamp = precise_time_ns();
-        self.delayed_composition_timer.schedule_composite(timestamp);
-        self.composition_request = CompositionRequest::DelayedComposite(timestamp);
-    }
-
     fn scroll_fragment_to_point(&mut self, id: ClipId, point: Point2D<f32>) {
         self.webrender_api.scroll_node_with_id(LayoutPoint::from_untyped(&point), id,
                                                ScrollClamping::ToContentBounds);
@@ -1235,13 +1205,18 @@ impl<Window: WindowMethods> IOCompositor<Window> {
                    pipeline_ids.push(*pipeline_id);
             }
         }
+        let animation_state = if pipeline_ids.is_empty() {
+            windowing::AnimationState::Idle
+        } else {
+            windowing::AnimationState::Animating
+        };
+        self.window.set_animation_state(animation_state);
         for pipeline_id in &pipeline_ids {
             self.tick_animations_for_pipeline(*pipeline_id)
         }
     }
 
     fn tick_animations_for_pipeline(&mut self, pipeline_id: PipelineId) {
-        self.schedule_delayed_composite_if_necessary();
         let animation_callbacks_running = self.pipeline_details(pipeline_id).animation_callbacks_running;
         if animation_callbacks_running {
             let msg = ConstellationMsg::TickAnimation(pipeline_id, AnimationTickType::Script);
@@ -1635,14 +1610,6 @@ impl<Window: WindowMethods> IOCompositor<Window> {
                 _ => compositor_messages.push(msg),
             }
         }
-        if found_recomposite_msg {
-            compositor_messages.retain(|msg| {
-                match *msg {
-                    Msg::DelayedCompositionTimeout(_) => false,
-                    _ => true,
-                }
-            })
-        }
         for msg in compositor_messages {
             if !self.handle_browser_message(msg) {
                 break
@@ -1664,8 +1631,7 @@ impl<Window: WindowMethods> IOCompositor<Window> {
         }
 
         match self.composition_request {
-            CompositionRequest::NoCompositingNecessary |
-            CompositionRequest::DelayedComposite(_) => {}
+            CompositionRequest::NoCompositingNecessary => {}
             CompositionRequest::CompositeNow(_) => {
                 self.composite()
             }

components/compositing/compositor_thread.rs

@@ -100,8 +100,6 @@ pub enum Msg {
     HistoryChanged(Vec<LoadData>, usize),
     /// Wether or not to follow a link
     AllowNavigation(ServoUrl, IpcSender<bool>),
-    /// We hit the delayed composition timeout. (See `delayed_composition.rs`.)
-    DelayedCompositionTimeout(u64),
     /// Composite.
     Recomposite(CompositingReason),
     /// Sends an unconsumed key event back to the compositor.
@@ -160,7 +158,6 @@ impl Debug for Msg {
             Msg::AllowNavigation(..) => write!(f, "AllowNavigation"),
             Msg::LoadStart => write!(f, "LoadStart"),
             Msg::HistoryChanged(..) => write!(f, "HistoryChanged"),
-            Msg::DelayedCompositionTimeout(..) => write!(f, "DelayedCompositionTimeout"),
             Msg::Recomposite(..) => write!(f, "Recomposite"),
             Msg::KeyEvent(..) => write!(f, "KeyEvent"),
             Msg::TouchEventProcessed(..) => write!(f, "TouchEventProcessed"),

components/compositing/delayed_composition.rs

@@ -1,107 +0,0 @@
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-//! A timer thread that composites near the end of the frame.
-//!
-//! This is useful when we need to composite next frame but we want to opportunistically give the
-//! painting thread time to paint if it can.
-
-use compositor_thread::{CompositorProxy, Msg};
-use std::sync::mpsc::{Receiver, Sender, channel};
-use std::thread::{self, Builder};
-use std::time::Duration;
-use std::u32;
-use time;
-
-/// The amount of time in nanoseconds that we give to the painting thread to paint. When this
-/// expires, we give up and composite anyway.
-static TIMEOUT: u64 = 12_000_000;
-
-pub struct DelayedCompositionTimerProxy {
-    sender: Sender<ToDelayedCompositionTimerMsg>,
-}
-
-struct DelayedCompositionTimer {
-    compositor_proxy: CompositorProxy,
-    receiver: Receiver<ToDelayedCompositionTimerMsg>,
-}
-
-enum ToDelayedCompositionTimerMsg {
-    Exit,
-    ScheduleComposite(u64),
-}
-
-impl DelayedCompositionTimerProxy {
-    pub fn new(compositor_proxy: CompositorProxy) -> DelayedCompositionTimerProxy {
-        let (to_timer_sender, to_timer_receiver) = channel();
-        Builder::new().spawn(move || {
-            let mut timer = DelayedCompositionTimer {
-                compositor_proxy: compositor_proxy,
-                receiver: to_timer_receiver,
-            };
-            timer.run();
-        }).unwrap();
-        DelayedCompositionTimerProxy {
-            sender: to_timer_sender,
-        }
-    }
-
-    pub fn schedule_composite(&mut self, timestamp: u64) {
-        self.sender.send(ToDelayedCompositionTimerMsg::ScheduleComposite(timestamp)).unwrap()
-    }
-
-    pub fn shutdown(&mut self) {
-        self.sender.send(ToDelayedCompositionTimerMsg::Exit).unwrap()
-    }
-}
-
-impl DelayedCompositionTimer {
-    fn run(&mut self) {
-        'outer: loop {
-            let mut timestamp;
-            loop {
-                match self.receiver.recv() {
-                    Ok(ToDelayedCompositionTimerMsg::ScheduleComposite(this_timestamp)) => {
-                        timestamp = this_timestamp;
-                        break
-                    }
-                    Ok(ToDelayedCompositionTimerMsg::Exit) => break 'outer,
-                    _ => break 'outer,
-                }
-            }
-
-            // Drain all messages from the queue.
-            loop {
-                match self.receiver.try_recv() {
-                    Ok(ToDelayedCompositionTimerMsg::ScheduleComposite(this_timestamp)) => {
-                        timestamp = this_timestamp;
-                        break
-                    }
-                    _ => break,
-                }
-            }
-
-            let target = timestamp + TIMEOUT;
-            let now = time::precise_time_ns();
-            if target > now {
-                let delta_ns = target - now;
-                thread::sleep(duration_from_nanoseconds(delta_ns));
-            }
-            self.compositor_proxy.send(Msg::DelayedCompositionTimeout(timestamp));
-        }
-    }
-}
-
-fn duration_from_nanoseconds(nanos: u64) -> Duration {
-    pub const NANOS_PER_SEC: u32 = 1_000_000_000;
-
-    // Get number of seconds.
-    let secs = nanos / NANOS_PER_SEC as u64;
-
-    // Get number of extra nanoseconds. This should always fit in a u32, but check anyway.
-    let subsec_nanos = nanos % NANOS_PER_SEC as u64;
-    assert!(subsec_nanos <= u32::MAX as u64);
-
-    Duration::new(secs, subsec_nanos as u32)
-}

components/compositing/lib.rs

@@ -35,7 +35,6 @@ use style_traits::CSSPixel;
 
 mod compositor;
 pub mod compositor_thread;
-mod delayed_composition;
 mod touch;
 pub mod windowing;
 

components/compositing/windowing.rs

@@ -102,6 +102,12 @@ impl Debug for WindowEvent {
     }
 }
 
+#[derive(Debug, Copy, Clone, PartialEq)]
+pub enum AnimationState {
+    Idle,
+    Animating,
+}
+
 pub trait WindowMethods {
     /// Returns the rendering area size in hardware pixels.
     fn framebuffer_size(&self) -> TypedSize2D<u32, DevicePixel>;
@@ -163,4 +169,10 @@ pub trait WindowMethods {
 
     /// Return the GL function pointer trait.
     fn gl(&self) -> Rc<gl::Gl>;
+
+    /// Set whether the application is currently animating.
+    /// Typically, when animations are active, the window
+    /// will want to avoid blocking on UI events, and just
+    /// run the event loop at the vsync interval.
+    fn set_animation_state(&self, _state: AnimationState) {}
 }

components/script/dom/document.rs

@@ -1538,28 +1538,29 @@ impl Document {
         self.animation_frame_ident.set(ident);
         self.animation_frame_list.borrow_mut().push((ident, Some(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
-        if !self.running_animation_callbacks.get() {
-            if !self.is_faking_animation_frames() {
-                let global_scope = self.window.upcast::<GlobalScope>();
-                let event = ConstellationMsg::ChangeRunningAnimationsState(
-                    global_scope.pipeline_id(),
-                    AnimationState::AnimationCallbacksPresent);
-                global_scope.constellation_chan().send(event).unwrap();
-            } else {
-                let callback = FakeRequestAnimationFrameCallback {
-                    document: Trusted::new(self),
-                };
-                self.global()
-                    .schedule_callback(OneshotTimerCallback::FakeRequestAnimationFrame(callback),
-                                       MsDuration::new(FAKE_REQUEST_ANIMATION_FRAME_DELAY));
-            }
+
+        // If we are running 'fake' animation frames, we unconditionally
+        // set up a one-shot timer for script to execute the rAF callbacks.
+        if self.is_faking_animation_frames() {
+            let callback = FakeRequestAnimationFrameCallback {
+                document: Trusted::new(self),
+            };
+            self.global()
+                .schedule_callback(OneshotTimerCallback::FakeRequestAnimationFrame(callback),
+                                   MsDuration::new(FAKE_REQUEST_ANIMATION_FRAME_DELAY));
+        } else if !self.running_animation_callbacks.get() {
+            // 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.
+
+            let global_scope = self.window.upcast::<GlobalScope>();
+            let event = ConstellationMsg::ChangeRunningAnimationsState(
+                global_scope.pipeline_id(),
+                AnimationState::AnimationCallbacksPresent);
+            global_scope.constellation_chan().send(event).unwrap();
         }
 
         ident
@@ -1596,6 +1597,22 @@ impl Document {
                                            ReflowQueryType::NoQuery,
                                            ReflowReason::RequestAnimationFrame);
 
+        if spurious && !was_faking_animation_frames {
+            // If the rAF callbacks did not mutate the DOM, then the
+            // reflow call above means that layout will not be invoked,
+            // and therefore no new frame will be sent to the compositor.
+            // If this happens, the compositor will not tick the animation
+            // and the next rAF will never be called! When this happens
+            // for several frames, then the spurious rAF detection below
+            // will kick in and use a timer to tick the callbacks. However,
+            // for the interim frames where we are deciding whether this rAF
+            // is considered spurious, we need to ensure that the layout
+            // and compositor *do* tick the animation.
+            self.window.force_reflow(ReflowGoal::ForDisplay,
+                                     ReflowQueryType::NoQuery,
+                                     ReflowReason::RequestAnimationFrame);
+        }
+
         // Only send the animation change state message after running any callbacks.
         // This means that if the animation callback adds a new callback for
         // the next frame (which is the common case), we won't send a NoAnimationCallbacksPresent

ports/glutin/window.rs

@@ -6,7 +6,7 @@
 
 use NestedEventLoopListener;
 use compositing::compositor_thread::EventLoopWaker;
-use compositing::windowing::{MouseWindowEvent, WindowNavigateMsg};
+use compositing::windowing::{AnimationState, MouseWindowEvent, WindowNavigateMsg};
 use compositing::windowing::{WindowEvent, WindowMethods};
 use euclid::{Point2D, Size2D, TypedPoint2D, TypedVector2D, TypedRect, ScaleFactor, TypedSize2D};
 #[cfg(target_os = "windows")]
@@ -196,6 +196,8 @@ pub struct Window {
     #[cfg(not(target_os = "windows"))]
     pressed_key_map: RefCell<Vec<(ScanCode, char)>>,
 
+    animation_state: Cell<AnimationState>,
+
     gl: Rc<gl::Gl>,
 }
 
@@ -316,6 +318,7 @@ impl Window {
             #[cfg(target_os = "windows")]
             last_pressed_key: Cell::new(None),
             gl: gl.clone(),
+            animation_state: Cell::new(AnimationState::Idle),
         };
 
         window.present();
@@ -655,10 +658,14 @@ impl Window {
         let mut events = mem::replace(&mut *self.event_queue.borrow_mut(), Vec::new());
         let mut close_event = false;
 
+        let poll = self.animation_state.get() == AnimationState::Animating ||
+                   opts::get().output_file.is_some() ||
+                   opts::get().exit_after_load ||
+                   opts::get().headless;
         // When writing to a file then exiting, use event
         // polling so that we don't block on a GUI event
         // such as mouse click.
-        if opts::get().output_file.is_some() || opts::get().exit_after_load || opts::get().headless {
+        if poll {
             match self.kind {
                 WindowKind::Window(ref window) => {
                     while let Some(event) = window.poll_events().next() {
@@ -1005,6 +1012,10 @@ impl WindowMethods for Window {
 
     }
 
+    fn set_animation_state(&self, state: AnimationState) {
+        self.animation_state.set(state);
+    }
+
     fn set_inner_size(&self, size: Size2D<u32>) {
         match self.kind {
             WindowKind::Window(ref window) => {