Creating a helper class for reversing timing functions.

Source/core/animation/CompositorAnimations.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 21 matching lines @@
 #define CompositorAnimations_h
 
 #include "core/animation/Timing.h"
 #include "wtf/Vector.h"
 
 namespace WebCore {
 
 class Element;
 class AnimationEffect;
 
+// Given an input timing function between keyframe at 0 and keyframe at 1.0, we
+// need a timing function such that the behavior with the keyframes swapped is
+// equivalent to reversing time with the input timing function and keyframes.
+// This means flipping the timing function about x=0.5 and about y=0.5.
+// FIXME: Remove once the Compositor natively understands reversing time.
+class CompositorAnimationsTimingFunctionReverser {
+public:
+    static PassRefPtr<TimingFunction> reverse(const LinearTimingFunction* timefunc);
+    static PassRefPtr<TimingFunction> reverse(const CubicBezierTimingFunction* timefunc);
+    static PassRefPtr<TimingFunction> reverse(const ChainedTimingFunction* timefunc);
+    static PassRefPtr<TimingFunction> reverse(const TimingFunction* timefunc);
+};
+
 class CompositorAnimations {
 
 public:
     static CompositorAnimations* instance() { return instance(0); }
     static void setInstanceForTesting(CompositorAnimations* newInstance) { instance(newInstance); }
 
     virtual bool isCandidateForCompositorAnimation(const Timing&, const AnimationEffect*);
     virtual bool canStartCompositorAnimation(const Element*);
     virtual void startCompositorAnimation(const Element*, const Timing&, const AnimationEffect*, Vector<int>& startedAnimationIds);
     virtual void cancelCompositorAnimation(const Element*, int id);
 
 protected:
     CompositorAnimations() { }
 
 private:
     static CompositorAnimations* instance(CompositorAnimations* newInstance = 0)
     {
         static CompositorAnimations* instance = new CompositorAnimations();
         if (newInstance) {
             instance = newInstance;
         }
         return instance;
     }
 };
 
 } // namespace WebCore
 
 #endif