Takeover MT initiated animations from the compositor

third_party/WebKit/Source/platform/scroll/ScrollAnimator.cpp

 /*
  * Copyright (c) 2011, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 125 matching lines @@
     if (m_runState == RunState::PostAnimationCleanup)
         resetAnimationState();
 
     if (m_animationCurve && m_runState != RunState::WaitingToCancelOnCompositor) {
         if ((targetPos - m_targetOffset).isZero())
             return true;
 
         m_targetOffset = targetPos;
         ASSERT(m_runState == RunState::RunningOnMainThread
             || m_runState == RunState::RunningOnCompositor
-            || m_runState == RunState::RunningOnCompositorButNeedsUpdate);
+            || m_runState == RunState::RunningOnCompositorButNeedsUpdate
+            || m_runState == RunState::RunningOnCompositorButNeedsTakeover);
 
-        if (m_runState == RunState::RunningOnCompositor
-            || m_runState == RunState::RunningOnCompositorButNeedsUpdate) {
-            if (registerAndScheduleAnimation())
-                m_runState = RunState::RunningOnCompositorButNeedsUpdate;
+        // Running on the main thread, simply update the target offset instead
+        // of sending to the compositor.
+        if (m_runState == RunState::RunningOnMainThread) {
+            m_animationCurve->updateTarget(m_timeFunction() - m_startTime, targetPos);
             return true;
         }
 
-        // Running on the main thread, simply update the target offset instead
-        // of sending to the compositor.
-        m_animationCurve->updateTarget(m_timeFunction() - m_startTime, targetPos);
+        if (registerAndScheduleAnimation())
+            m_runState = RunState::RunningOnCompositorButNeedsUpdate;
         return true;
     }
 
     if ((targetPos - currentPosition()).isZero())
         return false;
 
     m_targetOffset = targetPos;
     m_startTime = m_timeFunction();
 
     if (registerAndScheduleAnimation())
@@ skipping 37 matching lines @@
 
 void ScrollAnimator::postAnimationCleanupAndReset()
 {
     // Remove the temporary main thread scrolling reason that was added while
     // main thread had scheduled an animation.
     removeMainThreadScrollingReason();
 
     resetAnimationState();
 }
 
+bool ScrollAnimator::sendAnimationToCompositor()
+{
+    bool sentToCompositor = false;
+    if (!m_scrollableArea->shouldScrollOnMainThread()) {

[jbroman, 2016/03/07 18:38:40]

super-nit: this might be a little easier to read with early return:

if (m_scrollableArea->shouldScrollOnMainThread())
    return false;

OwnPtr<CompositorAnimation> animation = ...;
// ...
bool sentToCompositor = addAnimation(animation.release();
if (sentToCompositor) {
     // ...
}
return sentToCompositor;

It reduces the level of indentation, and I know immediately that
if the scrollable area is on the main thread that nothing happens,
without having to read past the if statement.

[ymalik, 2016/03/07 21:26:06]

Agreed. Done!

+        OwnPtr<CompositorAnimation> animation = adoptPtr(
+            CompositorFactory::current().createAnimation(
+                *m_animationCurve,
+                CompositorTargetProperty::SCROLL_OFFSET));
+        // Being here means that either there is an animation that needs
+        // to be sent to the compositor, or an animation that needs to
+        // be updated (a new scroll event before the previous animation
+        // is finished). In either case, the start time is when the
+        // first animation was initiated. This re-targets the animation
+        // using the current time on main thread.
+        animation->setStartTime(m_startTime);
+
+        int animationId = animation->id();
+        int animationGroupId = animation->group();
+
+        sentToCompositor = addAnimation(animation.release());
+        if (sentToCompositor) {
+            m_runState = RunState::RunningOnCompositor;
+            m_compositorAnimationId = animationId;
+            m_compositorAnimationGroupId = animationGroupId;
+        }
+    }
+    return sentToCompositor;
+}
+
 void ScrollAnimator::updateCompositorAnimations()
 {
     if (m_runState == RunState::PostAnimationCleanup) {
         postAnimationCleanupAndReset();
         return;
     }
 
     if (m_compositorAnimationId && m_runState != RunState::RunningOnCompositor
         && m_runState != RunState::RunningOnCompositorButNeedsUpdate) {
         // If the current run state is WaitingToSendToCompositor but we have a
         // non-zero compositor animation id, there's a currently running
         // compositor animation that needs to be removed here before the new
         // animation is added below.
         ASSERT(m_runState == RunState::WaitingToCancelOnCompositor
-            || m_runState == RunState::WaitingToSendToCompositor);
+            || m_runState == RunState::WaitingToSendToCompositor
+            || m_runState == RunState::RunningOnCompositorButNeedsTakeover);
 
-        abortAnimation();
+        if (m_runState == RunState::RunningOnCompositorButNeedsTakeover) {
+            // The animation is already aborted when the call to
+            // ::takeoverCompositorAnimation is made.
+            m_runState = RunState::WaitingToSendToCompositor;
+        } else {
+            abortAnimation();
+        }
 
         m_compositorAnimationId = 0;
         m_compositorAnimationGroupId = 0;
         if (m_runState == RunState::WaitingToCancelOnCompositor) {
             postAnimationCleanupAndReset();
             return;
         }
     }
 
     if (m_runState == RunState::WaitingToSendToCompositor
@@ skipping 14 matching lines @@
         if (!m_animationCurve) {
             m_animationCurve = adoptPtr(CompositorFactory::current().createScrollOffsetAnimationCurve(
                 m_targetOffset,
                 CompositorAnimationCurve::TimingFunctionTypeEaseInOut,
                 m_lastGranularity == ScrollByPixel ?
                     CompositorScrollOffsetAnimationCurve::ScrollDurationInverseDelta :
                     CompositorScrollOffsetAnimationCurve::ScrollDurationConstant));
             m_animationCurve->setInitialValue(currentPosition());
         }
 
-        bool sentToCompositor = false;
-        if (!m_scrollableArea->shouldScrollOnMainThread()) {
-            OwnPtr<CompositorAnimation> animation = adoptPtr(
-                CompositorFactory::current().createAnimation(
-                    *m_animationCurve,
-                    CompositorTargetProperty::SCROLL_OFFSET));
-            // Being here means that either there is an animation that needs
-            // to be sent to the compositor, or an animation that needs to
-            // be updated (a new scroll event before the previous animation
-            // is finished). In either case, the start time is when the
-            // first animation was initiated. This re-targets the animation
-            // using the current time on main thread.
-            animation->setStartTime(m_startTime);
-
-            int animationId = animation->id();
-            int animationGroupId = animation->group();
-
-            sentToCompositor = addAnimation(animation.release());
-            if (sentToCompositor) {
-                m_runState = RunState::RunningOnCompositor;
-                m_compositorAnimationId = animationId;
-                m_compositorAnimationGroupId = animationGroupId;
-            }
-        }
-
         bool runningOnMainThread = false;
+        bool sentToCompositor = sendAnimationToCompositor();
         if (!sentToCompositor) {
             runningOnMainThread = registerAndScheduleAnimation();
             if (runningOnMainThread)
                 m_runState = RunState::RunningOnMainThread;
         }
 
         // Main thread should deal with the scroll animations it started.
         if (sentToCompositor || runningOnMainThread)
             addMainThreadScrollingReason();
         else
@@ skipping 49 matching lines @@
                 std::move(scrollOffsetAnimationCurve)));
         m_startTime = animationStartTime;
     }
 }
 
 void ScrollAnimator::cancelAnimation()
 {
     ScrollAnimatorCompositorCoordinator::cancelAnimation();
 }
 
+void ScrollAnimator::takeoverCompositorAnimation()
+{
+    if (m_runState == RunState::RunningOnCompositor
+        || m_runState ==  RunState::RunningOnCompositorButNeedsUpdate)
+        removeMainThreadScrollingReason();
+
+    ScrollAnimatorCompositorCoordinator::takeoverCompositorAnimation();
+}
+
 void ScrollAnimator::layerForCompositedScrollingDidChange(
     CompositorAnimationTimeline* timeline)
 {
     if (reattachCompositorPlayerIfNeeded(timeline) && m_animationCurve)
         addMainThreadScrollingReason();
 }
 
 bool ScrollAnimator::registerAndScheduleAnimation()
 {
     scrollableArea()->registerForAnimation();
     if (!m_scrollableArea->scheduleAnimation()) {
         scrollToOffsetWithoutAnimation(m_targetOffset);
         resetAnimationState();
         return false;
     }
     return true;
 }
 
 DEFINE_TRACE(ScrollAnimator)
 {
     ScrollAnimatorBase::trace(visitor);
 }
 
 } // namespace blink