Turning off blending for part of the animation to reduce jank.

ash/wm/window_animations.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/wm/window_animations.h"
 
 #include <math.h>
 
 #include <algorithm>
 #include <vector>
@@ skipping 131 matching lines @@
     window_->AddObserver(this);
   }
   virtual ~HidingWindowAnimationObserver() {
     STLDeleteElements(&layers_);
   }
 
  private:
   // Overridden from ui::ImplicitAnimationObserver:
   virtual void OnImplicitAnimationsCompleted() OVERRIDE {
     // Window may have been destroyed by this point.
-    if (window_)
+    if (window_) {
+      window_->layer()->SetVisible(false);

[sky, 2012/08/10 15:47:39]

If you do this then the TargetVisibility is true after invoking Hide(), which we
don't want and is likely to cause problems. I think this has to be @ 473.

[alexst (slow to review), 2012/08/10 17:50:55]

Ah, this was the wrong solution to a real problem.
Animation that hid the window was not sync'd with the minimize animation.
Solution in this patch was setting visibility at the end of the animation. New
patch will alter the implicit animation's time instead.

On 2012/08/10 15:47:39, sky wrote:

       window_->RemoveObserver(this);
+    }
     MessageLoop::current()->DeleteSoon(FROM_HERE, this);
   }
 
   // Overridden from aura::WindowObserver:
   virtual void OnWindowDestroying(aura::Window* window) OVERRIDE {
     DCHECK_EQ(window, window_);
     DCHECK(layers_.empty());
     AcquireAllLayers(window_);
 
     // If the Widget has views with layers, then it is necessary to take
@@ skipping 276 matching lines @@
   scoped_ptr<ui::LayerAnimationElement> transition(
       ui::LayerAnimationElement::CreateInterpolatedTransformElement(
           rotation_about_pivot.release(), duration));
 
   transition->set_tween_type(
       show ? ui::Tween::EASE_IN : ui::Tween::EASE_IN_OUT);
 
   window->layer()->GetAnimator()->ScheduleAnimation(
       new ui::LayerAnimationSequence(transition.release()));
 
+  // When hiding a window, turn off blending until the animation is
+  // 3 / 4 done to save bandwidth and reduce jank
+  if (!show) {
+    ui::LayerAnimationElement::AnimatableProperties propertiesToPause;
+    propertiesToPause.insert(ui::LayerAnimationElement::OPACITY);
+    window->layer()->GetAnimator()->ScheduleAnimation(
+      new ui::LayerAnimationSequence(
+          ui::LayerAnimationElement::CreatePauseElement(
+              propertiesToPause, (duration * 3 ) / 4)));
+  }
+
+  // Fade in and out quickly when the window is small to reduce jank
   float opacity = show ? 1.0f : 0.0f;
   window->layer()->GetAnimator()->ScheduleAnimation(
       new ui::LayerAnimationSequence(
-          ui::LayerAnimationElement::CreateOpacityElement(opacity, duration)));
+          ui::LayerAnimationElement::CreateOpacityElement(
+              opacity, duration / 4)));
 }
 
 void AnimateShowWindow_Minimize(aura::Window* window) {
   window->layer()->set_delegate(window);
   window->layer()->SetOpacity(kWindowAnimation_HideOpacity);
   AddLayerAnimationsForMinimize(window, true);
 
   // Now that the window has been restored, we need to clear its animation style
   // to default so that normal animation applies.
   SetWindowVisibilityAnimationType(
       window, WINDOW_VISIBILITY_ANIMATION_TYPE_DEFAULT);
 }
 
 void AnimateHideWindow_Minimize(aura::Window* window) {
   window->layer()->set_delegate(NULL);
 
   // Property sets within this scope will be implicitly animated.
   ui::ScopedLayerAnimationSettings settings(window->layer()->GetAnimator());
   settings.AddObserver(new HidingWindowAnimationObserver(window));
-  window->layer()->SetVisible(false);
 
   AddLayerAnimationsForMinimize(window, false);
 }
 
 void AnimateShowHideWindowCommon_BrightnessGrayscale(aura::Window* window,
                                                      bool show) {
   window->layer()->set_delegate(window);
 
   float start_value, end_value;
   if (show) {
@@ skipping 370 matching lines @@
         AnimateHideWindow(window);
   }
 }
 
 void SetDelayedOldLayerDeletionInCrossFadeForTest(bool value) {
   delayed_old_layer_deletion_in_cross_fade_for_test_ = value;
 }
 
 }  // namespace internal
 }  // namespace ash