WIP: Implement CSS transitions on top of InterpolationTypes instead of AnimatableValues

third_party/WebKit/Source/core/animation/Interpolation.h

 // Copyright 2014 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 Interpolation_h
 #define Interpolation_h
 
 #include "core/CoreExport.h"
 #include "core/animation/InterpolableValue.h"
 #include "wtf/Forward.h"
 #include "wtf/RefCounted.h"
 #include <memory>
 
 namespace blink {
 
 class PropertyHandle;
 
-// Represents an animation's effect between an adjacent pair of PropertySpecificKeyframes.
+// Represents an animation's effect between two values.
 class CORE_EXPORT Interpolation : public RefCounted<Interpolation> {
     WTF_MAKE_NONCOPYABLE(Interpolation);
 public:
-    virtual ~Interpolation();
+    // TODO(alancutter): Remove StyleInterpolation and LegacyStyleInterpolation and upstream StackableInterpolation as Interpolation.
+    virtual bool isStyleInterpolation() const { return false; }
+    virtual bool isLegacyStyleInterpolation() const { return false; }
 
-    virtual void interpolate(int iteration, double fraction);
+    virtual bool isStackableInterpolation() const { return false; }
+    virtual bool isKeyframeInterpolation() const { return false; }
+    virtual bool isPairwiseInterpolation() const { return false; }
 
-    virtual bool isStyleInterpolation() const { return false; }
-    virtual bool isInvalidatableInterpolation() const { return false; }
-    virtual bool isLegacyStyleInterpolation() const { return false; }
+    void interpolate(int iteration, double fraction)
+    {
+        if (iteration == m_currentIteration && fraction == m_currentFraction)
+            return;
+        m_currentIteration = iteration;
+        m_currentFraction = fraction;
+        interpolateImpl();
+    }
 
     virtual PropertyHandle getProperty() const = 0;
     virtual bool dependsOnUnderlyingValue() const { return false; }
 
+    virtual ~Interpolation() {}
+
 protected:
-    const std::unique_ptr<InterpolableValue> m_start;
-    const std::unique_ptr<InterpolableValue> m_end;
+    Interpolation()
+        : m_currentIteration(std::numeric_limits<double>::quiet_NaN())
+        , m_currentFraction(std::numeric_limits<double>::quiet_NaN())
+    { }
 
-    mutable double m_cachedFraction;
-    mutable int m_cachedIteration;
-    mutable std::unique_ptr<InterpolableValue> m_cachedValue;
+    virtual void interpolateImpl() = 0;
 
-    Interpolation(std::unique_ptr<InterpolableValue> start, std::unique_ptr<InterpolableValue> end);
-
-private:
-    InterpolableValue* getCachedValueForTesting() const { return m_cachedValue.get(); }
-
-    friend class AnimationInterpolableValueTest;
-    friend class AnimationInterpolationEffectTest;
-    friend class AnimationDoubleStyleInterpolationTest;
-    friend class AnimationVisibilityStyleInterpolationTest;
+    double m_currentIteration;
+    double m_currentFraction;
 };
 
 using ActiveInterpolations = Vector<RefPtr<Interpolation>, 1>;
 
 } // namespace blink
 
 #endif // Interpolation_h