ash: Make cross-fade duration based on area, not width

This better corresponds with the user's notion of the visual impact of the change, especially for animations where the width doesn't change much.

BUG=none
TEST=updated unit tests


Review URL: https://chromiumcodereview.appspot.com/10561031

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@142773 0039d316-1c4b-4281-b951-d872f2087c98

3 files changed, 31 insertions, 27 deletions

diff --git a/ash/wm/window_animations.cc b/ash/wm/window_animations.cc
index d5d11e5..1b222a2 100644
--- a/ash/wm/window_animations.cc
+++ b/ash/wm/window_animations.cc
@@ -649,8 +649,6 @@ ui::ImplicitAnimationObserver* CreateHidingWindowAnimationObserver(
   return new internal::HidingWindowAnimationObserver(window);
 }
 
-namespace internal {
-
 void CrossFadeToBounds(aura::Window* window, const gfx::Rect& new_bounds) {
   DCHECK(window->TargetVisibility());
   gfx::Rect old_bounds = window->bounds();
@@ -658,7 +656,7 @@ void CrossFadeToBounds(aura::Window* window, const gfx::Rect& new_bounds) {
   // Create fresh layers for the window and all its children to paint into.
   // Takes ownership of the old layer and all its children, which will be
   // cleaned up after the animation completes.
-  ui::Layer* old_layer = RecreateWindowLayers(window);
+  ui::Layer* old_layer = internal::RecreateWindowLayers(window);
   ui::Layer* new_layer = window->layer();
 
   // Ensure the higher-resolution layer is on top.
@@ -672,12 +670,12 @@ void CrossFadeToBounds(aura::Window* window, const gfx::Rect& new_bounds) {
   // aligned during the animation.
   const ui::Tween::Type kTransformTween = ui::Tween::EASE_OUT;
   // Shorten the animation if there's not much visual movement.
-  TimeDelta duration = GetCrossFadeDuration(old_bounds, new_bounds);
+  TimeDelta duration = internal::GetCrossFadeDuration(old_bounds, new_bounds);
   {
     // Scale up the old layer while translating to new position.
     ui::ScopedLayerAnimationSettings settings(old_layer->GetAnimator());
     // Animation observer owns the old layer and deletes itself.
-    settings.AddObserver(new CrossFadeObserver(window, old_layer));
+    settings.AddObserver(new internal::CrossFadeObserver(window, old_layer));
     settings.SetTransitionDuration(duration);
     settings.SetTweenType(kTransformTween);
     ui::Transform out_transform;
@@ -730,20 +728,24 @@ void CrossFadeToBounds(aura::Window* window, const gfx::Rect& new_bounds) {
   }
 }
 
+namespace internal {
+
 TimeDelta GetCrossFadeDuration(const gfx::Rect& old_bounds,
                                const gfx::Rect& new_bounds) {
-  int max_width = std::max(old_bounds.width(), new_bounds.width());
+  int old_area = old_bounds.width() * old_bounds.height();
+  int new_area = new_bounds.width() * new_bounds.height();
+  int max_area = std::max(old_area, new_area);
   // Avoid divide by zero.
-  if (max_width == 0)
+  if (max_area == 0)
     return TimeDelta();
 
-  int delta_width = std::abs(old_bounds.width() - new_bounds.width());
-  // If the width didn't change, the animation is instantaneous.
-  if (delta_width == 0)
+  int delta_area = std::abs(old_area - new_area);
+  // If the area didn't change, the animation is instantaneous.
+  if (delta_area == 0)
     return TimeDelta();
 
   float factor =
-      static_cast<float>(delta_width) / static_cast<float>(max_width);
+      static_cast<float>(delta_area) / static_cast<float>(max_area);
   const float kRange = kCrossFadeDurationMaxMs - kCrossFadeDurationMinMs;
   return TimeDelta::FromMilliseconds(
       Round64(kCrossFadeDurationMinMs + (factor * kRange)));
diff --git a/ash/wm/window_animations.h b/ash/wm/window_animations.h
index 1d1a9f7..0a7c0bc 100644
--- a/ash/wm/window_animations.h
+++ b/ash/wm/window_animations.h
@@ -74,12 +74,12 @@ ASH_EXPORT void SetWindowVisibilityAnimationVerticalPosition(
 ASH_EXPORT ui::ImplicitAnimationObserver* CreateHidingWindowAnimationObserver(
     aura::Window* window);
 
-namespace internal {
-
 // Animate a cross-fade of |window| from its current bounds to |new_bounds|.
 ASH_EXPORT void CrossFadeToBounds(aura::Window* window,
                                   const gfx::Rect& new_bounds);
 
+namespace internal {
+
 // Returns the duration of the cross-fade animation based on the |old_bounds|
 // and |new_bounds| of the window.
 ASH_EXPORT base::TimeDelta GetCrossFadeDuration(const gfx::Rect& old_bounds,
diff --git a/ash/wm/window_animations_unittest.cc b/ash/wm/window_animations_unittest.cc
index bf51c1e..489a401 100644
--- a/ash/wm/window_animations_unittest.cc
+++ b/ash/wm/window_animations_unittest.cc
@@ -173,25 +173,27 @@ TEST_F(WindowAnimationsTest, GetCrossFadeDuration) {
   EXPECT_EQ(0, GetCrossFadeDuration(screen, screen).InMilliseconds());
 
   // Small changes are fast.
-  gfx::Rect almost_screen(10, 10, 900, 400);
-  EXPECT_EQ(220, GetCrossFadeDuration(almost_screen, screen).InMilliseconds());
-  EXPECT_EQ(220, GetCrossFadeDuration(screen, almost_screen).InMilliseconds());
+  const int kMinimum = 100;
+  const int kRange = 300;
+  gfx::Rect almost_screen(10, 10, 1000, 450);  // 90% of screen area
+  EXPECT_EQ(kMinimum + kRange / 10,
+           GetCrossFadeDuration(almost_screen, screen).InMilliseconds());
+  EXPECT_EQ(kMinimum + kRange / 10,
+            GetCrossFadeDuration(screen, almost_screen).InMilliseconds());
 
   // Large changes are slow.
-  gfx::Rect small(10, 10, 100, 100);
-  EXPECT_EQ(380, GetCrossFadeDuration(small, screen).InMilliseconds());
-  EXPECT_EQ(380, GetCrossFadeDuration(screen, small).InMilliseconds());
+  gfx::Rect small(10, 10, 100, 500);  // 10% of screen area
+  EXPECT_EQ(kMinimum + kRange * 9 / 10,
+            GetCrossFadeDuration(small, screen).InMilliseconds());
+  EXPECT_EQ(kMinimum + kRange * 9 / 10,
+            GetCrossFadeDuration(screen, small).InMilliseconds());
 
   // Medium changes take medium time.
   gfx::Rect half_screen(10, 10, 500, 250);
-  EXPECT_EQ(300, GetCrossFadeDuration(half_screen, screen).InMilliseconds());
-  EXPECT_EQ(300, GetCrossFadeDuration(screen, half_screen).InMilliseconds());
-
-  // Change is based on width.
-  gfx::Rect narrow(10, 10, 100, 500);
-  gfx::Rect wide(10, 10, 900, 500);
-  EXPECT_EQ(380, GetCrossFadeDuration(narrow, screen).InMilliseconds());
-  EXPECT_EQ(220, GetCrossFadeDuration(wide, screen).InMilliseconds());
+  EXPECT_EQ(kMinimum + kRange * 3 / 4,
+            GetCrossFadeDuration(half_screen, screen).InMilliseconds());
+  EXPECT_EQ(kMinimum + kRange * 3 / 4,
+            GetCrossFadeDuration(screen, half_screen).InMilliseconds());
 }
 
 }  // namespace internal