Explicit animation support

ui/gfx/compositor/layer_animation_element.h

+// Copyright (c) 2011 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.
+
+#ifndef UI_GFX_COMPOSITOR_LAYER_ANIMATION_ELEMENT_H_
+#define UI_GFX_COMPOSITOR_LAYER_ANIMATION_ELEMENT_H_
+#pragma once
+
+#include <set>
+
+#include "base/memory/ref_counted.h"
+#include "base/time.h"
+
+namespace gfx {
+class Rect;
+}  // gfx
+
+namespace ui {
+
+class LayerAnimationDelegate;
+class Transform;
+
+// LayerAnimationElements represent one segment of an animation between two
+// keyframes. They know how to update a LayerAnimationDelegate given a value
+// between 0 and 1 (0 for the last keyframe, and one for the next).
+class LayerAnimationElement : public base::RefCounted<LayerAnimationElement> {

[sky, 2011/10/14 16:39:52]

Can we make the ownership model trivial and have the animator own these?

+ public:
+  enum AnimatableProperty {
+    TRANSFORM = 0,
+    BOUNDS,
+    OPACITY
+  };
+
+  typedef std::set<AnimatableProperty> AnimatableProperties;
+
+  static LayerAnimationElement* CreateTransformElement(
+      const Transform& transform, base::TimeDelta duration);

[sky, 2011/10/14 16:39:52]

wrap each param.

+  static LayerAnimationElement* CreateBoundsElement(
+      const gfx::Rect& bounds, base::TimeDelta duration);
+  static LayerAnimationElement* CreateOpacityElement(
+      float opacity, base::TimeDelta duration);
+  static LayerAnimationElement* CreatePauseElement(
+      AnimatableProperty property, base::TimeDelta duration);
+
+  // Updates the delegate to the appropriate value for |t|, which is in the
+  // range [0, 1] where 0 represents the last keyframe and 1 represents the
+  // next. If the animation is not aborted, it is guaranteed that animate will

[sky, 2011/10/14 16:39:52]

animate -> progress

+  // eventually be called with t = 1.0.
+  virtual void Progress(double t, LayerAnimationDelegate* delegate) = 0;

[sky, 2011/10/14 16:39:52]

I think this should be time based, otherwise we could never support infinite
animations.

+
+  // Called if the animation is not allowed to complete.
+  virtual void Abort() = 0;
+
+  // The properties that the element modifies.
+  virtual const AnimatableProperties& Properties() const = 0;

[sky, 2011/10/14 16:39:52]

Can you think of a case where the properties or duration need to change after
constructed? It seems better to make these concrete with the values provided to
the constructor.

+
+  // The duration of the animation
+  virtual base::TimeDelta Duration() const = 0;
+
+ protected:
+  friend class base::RefCounted<LayerAnimationElement>;
+  virtual ~LayerAnimationElement() {}
+};
+
+}  // namespace ui
+
+#endif  // UI_GFX_COMPOSITOR_LAYER_ANIMATION_ELEMENT_H_