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

ash/wm/window_animations.cc

Index: ash/wm/window_animations.cc
diff --git a/ash/wm/window_animations.cc b/ash/wm/window_animations.cc
index b3f80e34d66e6dc6664f20fce0dea976a1cb4046..d7e4ca3777f7090aa0418b16fbba3b89fc383be3 100644
--- a/ash/wm/window_animations.cc
+++ b/ash/wm/window_animations.cc
@@ -149,8 +149,10 @@ class HidingWindowAnimationObserver : public ui::ImplicitAnimationObserver,
   // 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);
   }
 
@@ -447,10 +449,23 @@ void AddLayerAnimationsForMinimize(aura::Window* window, bool show) {
   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) {
@@ -470,7 +485,6 @@ void AnimateHideWindow_Minimize(aura::Window* window) {
   // 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);
 }