Fix animation smoothness when using requestAnimationFrame.

components/compositing/compositor.rs

@@ -2,6 +2,7 @@
  * 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/. */
 
+use AnimationTickType;
 use CompositorMsg as ConstellationMsg;
 use app_units::Au;
 use compositor_layer::{CompositorData, CompositorLayer, RcCompositorLayer, WantsScrollEventsFlag};
@@ -1550,7 +1551,13 @@ impl<Window: WindowMethods> IOCompositor<Window> {
 
     fn tick_animations_for_pipeline(&mut self, pipeline_id: PipelineId) {
         self.schedule_delayed_composite_if_necessary();
-        self.constellation_chan.send(ConstellationMsg::TickAnimation(pipeline_id)).unwrap()
+        let animation_callbacks_running = self.pipeline_details(pipeline_id).animation_callbacks_running;
+        let animation_type = if animation_callbacks_running {
+            AnimationTickType::Script
+        } else {
+            AnimationTickType::Layout
+        };
+        self.constellation_chan.send(ConstellationMsg::TickAnimation(pipeline_id, animation_type)).unwrap()
     }
 
     fn constrain_viewport(&mut self, pipeline_id: PipelineId, constraints: ViewportConstraints) {

components/compositing/constellation.rs

@@ -9,6 +9,7 @@
 //! navigation context, each `Pipeline` encompassing a `ScriptThread`,
 //! `LayoutThread`, and `PaintThread`.
 
+use AnimationTickType;
 use CompositorMsg as FromCompositorMsg;
 use canvas::canvas_paint_thread::CanvasPaintThread;
 use canvas::webgl_paint_thread::WebGLPaintThread;
@@ -585,8 +586,8 @@ impl<LTF: LayoutThreadFactory, STF: ScriptThreadFactory> Constellation<LTF, STF>
                 debug!("constellation got window resize message");
                 self.handle_resized_window_msg(new_size);
             }
-            Request::Compositor(FromCompositorMsg::TickAnimation(pipeline_id)) => {
-                self.handle_tick_animation(pipeline_id)
+            Request::Compositor(FromCompositorMsg::TickAnimation(pipeline_id, tick_type)) => {
+                self.handle_tick_animation(pipeline_id, tick_type)
             }
             Request::Compositor(FromCompositorMsg::WebDriverCommand(command)) => {
                 debug!("constellation got webdriver command message");
@@ -912,12 +913,22 @@ impl<LTF: LayoutThreadFactory, STF: ScriptThreadFactory> Constellation<LTF, STF>
                                                                                animation_state))
     }
 
-    fn handle_tick_animation(&mut self, pipeline_id: PipelineId) {
-        self.pipeline(pipeline_id)
-            .layout_chan
-            .0
-            .send(LayoutControlMsg::TickAnimations)
-            .unwrap();
+    fn handle_tick_animation(&mut self, pipeline_id: PipelineId, tick_type: AnimationTickType) {
+        match tick_type {
+            AnimationTickType::Script => {
+                self.pipeline(pipeline_id)
+                    .script_chan
+                    .send(ConstellationControlMsg::TickAllAnimations(pipeline_id))
+                    .unwrap();
+            }
+            AnimationTickType::Layout => {
+                self.pipeline(pipeline_id)
+                    .layout_chan
+                    .0
+                    .send(LayoutControlMsg::TickAnimations)
+                    .unwrap();
+            }
+        }
     }
 
     fn handle_load_url_msg(&mut self, source_id: PipelineId, load_data: LoadData) {

components/compositing/headless.rs

@@ -2,6 +2,7 @@
  * 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/. */
 
+use AnimationTickType;
 use CompositorMsg as ConstellationMsg;
 use compositor_thread::{CompositorEventListener, CompositorReceiver};
 use compositor_thread::{InitialCompositorState, Msg};
@@ -98,7 +99,7 @@ impl CompositorEventListener for NullCompositor {
                     AnimationState::NoAnimationsPresent |
                     AnimationState::NoAnimationCallbacksPresent => {}
                     AnimationState::AnimationCallbacksPresent => {
-                        let msg = ConstellationMsg::TickAnimation(pipeline_id);
+                        let msg = ConstellationMsg::TickAnimation(pipeline_id, AnimationTickType::Script);
                         self.constellation_chan.send(msg).unwrap()
                     }
                 }

components/compositing/lib.rs

@@ -76,6 +76,13 @@ mod timer_scheduler;
 mod touch;
 pub mod windowing;
 
+/// Specifies whether the script or layout thread needs to be ticked for animation.
+#[derive(Deserialize, Serialize)]
+pub enum AnimationTickType {
+    Script,
+    Layout,
+}
+
 /// Messages from the compositor to the constellation.
 #[derive(Deserialize, Serialize)]
 pub enum CompositorMsg {
@@ -98,7 +105,7 @@ pub enum CompositorMsg {
     Navigate(Option<(PipelineId, SubpageId)>, NavigationDirection),
     ResizedWindow(WindowSizeData),
     /// Requests that the constellation instruct layout to begin a new tick of the animation.
-    TickAnimation(PipelineId),
+    TickAnimation(PipelineId, AnimationTickType),
     /// Dispatch a webdriver command
     WebDriverCommand(WebDriverCommandMsg),
 }

components/layout/layout_thread.rs

@@ -1202,10 +1202,6 @@ impl LayoutThread {
     fn tick_all_animations<'a, 'b>(&mut self, possibly_locked_rw_data: &mut RwData<'a, 'b>) {
         let mut rw_data = possibly_locked_rw_data.lock();
         self.tick_animations(&mut rw_data);
-
-        self.script_chan
-            .send(ConstellationControlMsg::TickAllAnimations(self.id))
-            .unwrap();
     }
 
     pub fn tick_animations(&mut self, rw_data: &mut LayoutThreadData) {