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 47 matching lines @@
 DEFINE_WINDOW_PROPERTY_KEY(WindowVisibilityAnimationTransition,
                            kWindowVisibilityAnimationTransitionKey,
                            ANIMATE_BOTH);
 DEFINE_WINDOW_PROPERTY_KEY(float,
                            kWindowVisibilityAnimationVerticalPositionKey,
                            kWindowAnimation_Vertical_TranslateY);
 
 namespace {
 
 const int kDefaultAnimationDurationForMenuMS = 150;
+const int kLayerAnimationsForMinimizeDurationMS = 350;
 
 // Durations for the cross-fade animation, in milliseconds.
 const float kCrossFadeDurationMinMs = 100.f;
 const float kCrossFadeDurationMaxMs = 400.f;
 
 // Durations for the brightness/grayscale fade animation, in milliseconds.
 const int kBrightnessGrayscaleFadeDurationMs = 1000;
 
 // Brightness/grayscale values for hide/show window animations.
 const float kWindowAnimation_HideBrightnessGrayscale = 1.f;
@@ skipping 350 matching lines @@
   scoped_ptr<ui::InterpolatedTransform> rotation_about_pivot(
       new ui::InterpolatedTransformAboutPivot(
           gfx::Point(bounds.width() * 0.5, bounds.height() * 0.5),
           rotation.release()));
 
   scale->SetChild(translation.release());
   rotation_about_pivot->SetChild(scale.release());
 
   rotation_about_pivot->SetReversed(show);
 
-  base::TimeDelta duration = base::TimeDelta::FromMilliseconds(350);
+  base::TimeDelta duration = base::TimeDelta::FromMilliseconds(
+      kLayerAnimationsForMinimizeDurationMS);
 
   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());
+  base::TimeDelta duration = base::TimeDelta::FromMilliseconds(
+      kLayerAnimationsForMinimizeDurationMS);
+  settings.SetTransitionDuration(duration);
   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);
 
@@ skipping 377 matching lines @@
         AnimateHideWindow(window);
   }
 }
 
 void SetDelayedOldLayerDeletionInCrossFadeForTest(bool value) {
   delayed_old_layer_deletion_in_cross_fade_for_test_ = value;
 }
 
 }  // namespace internal
 }  // namespace ash