Add support for inverse transform animations.

ui/compositor/layer_animation_element_unittest.cc

Index: ui/compositor/layer_animation_element_unittest.cc
diff --git a/ui/compositor/layer_animation_element_unittest.cc b/ui/compositor/layer_animation_element_unittest.cc
index 2701200c0146488f0f1b8a9dfd2c2f26f713c4b7..e7b4c00b85d56fcee6119ed8559c95137871e02c 100644
--- a/ui/compositor/layer_animation_element_unittest.cc
+++ b/ui/compositor/layer_animation_element_unittest.cc
@@ -23,7 +23,7 @@ namespace {
 // that the element can be reused after it completes.
 TEST(LayerAnimationElementTest, TransformElement) {
   TestLayerAnimationDelegate delegate;
-  gfx::Transform start_transform, target_transform, middle_transform;
+  gfx::Transform start_transform, target_transform;
   start_transform.Rotate(-30.0);
   target_transform.Rotate(30.0);
   base::TimeTicks start_time;
@@ -65,6 +65,61 @@ TEST(LayerAnimationElementTest, TransformElement) {
   CheckApproximatelyEqual(target_transform, target_value.transform);
 }
 
+// Checks that the equation Child_start * Parent_start = Child_current *
+// Parent_current is true.
+TEST(LayerAnimationElementTest, CounterTransformElement) {
+  TestLayerAnimationDelegate delegate, parent_delegate;
+  gfx::Transform parent_start, parent_target;
+  parent_start.Scale(0.5, 3);
+  parent_start.Translate(-20, 30);
+  parent_target.Translate(0, 100);
+
+  gfx::Transform child_transform;
+  child_transform.Rotate(-30.0);
+
+  const gfx::Transform effective_child_transform =
+      child_transform * parent_start;
+
+  base::TimeTicks start_time;
+  base::TimeTicks now;
+  base::TimeDelta duration = base::TimeDelta::FromSeconds(1);
+
+  start_time += 5 * duration;
+  scoped_ptr<LayerAnimationElement> element(
+      LayerAnimationElement::CreateInverseTransformElement(parent_start,
+                                                           parent_target,
+                                                           duration));
+  element->set_animation_group_id(1);
+  scoped_ptr<LayerAnimationElement> parent_element(
+      LayerAnimationElement::CreateTransformElement(parent_target, duration));
+
+  parent_delegate.SetTransformFromAnimation(parent_start);
+  delegate.SetTransformFromAnimation(child_transform);
+
+  parent_element->set_requested_start_time(start_time);
+  parent_element->Start(&parent_delegate, 1);
+  parent_element->set_effective_start_time(start_time);
+  parent_element->Progress(start_time, &parent_delegate);
+
+  element->set_requested_start_time(start_time);
+  element->Start(&delegate, 1);
+  element->set_effective_start_time(start_time);
+  element->Progress(start_time, &delegate);
+  CheckApproximatelyEqual(effective_child_transform,
+                          delegate.GetTransformForAnimation() *
+                          parent_delegate.GetTransformForAnimation());
+  const int steps = 1000;
+  now = start_time;
+  for (int i = 0; i != steps; ++i) {
+    now += duration/steps;
+    parent_element->Progress(start_time, &parent_delegate);
+    element->Progress(start_time, &delegate);
+    CheckApproximatelyEqual(effective_child_transform,
+                            delegate.GetTransformForAnimation() *

[ajuma, 2013/08/20 15:32:41]

For threaded animations, the delegate won't actually get updated as the
animation progresses in LayerAnimationElementTests (since we don't actually have
a compositor). So these are going to be stuck at their initial value. Consider
checking the math by directly instantiating the corresponding
TransformAnimationCurveAdapters and calling GetValue on them.

[avallee, 2013/08/22 22:21:59]

Moved this test to a new test file for the transform curve adapters.

Would it still make sense to simulate an animation here?

+                            parent_delegate.GetTransformForAnimation());
+  }
+}
+
 // Check that the bounds element progresses the delegate as expected and
 // that the element can be reused after it completes.
 TEST(LayerAnimationElementTest, BoundsElement) {