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 * in the documentation and/or other materials provided with the
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#ifndef SKY_ENGINE_PLATFORM_SCROLL_SCROLLANIMATOR_H_
#define SKY_ENGINE_PLATFORM_SCROLL_SCROLLANIMATOR_H_

#include "sky/engine/platform/PlatformExport.h"
#include "sky/engine/platform/PlatformWheelEvent.h"
#include "sky/engine/platform/geometry/FloatSize.h"
#include "sky/engine/platform/scroll/ScrollTypes.h"
#include "sky/engine/wtf/FastAllocBase.h"
#include "sky/engine/wtf/Forward.h"
#include "sky/engine/wtf/Noncopyable.h"

namespace blink {

class FloatPoint;
class ScrollableArea;
class Scrollbar;

class PLATFORM_EXPORT ScrollAnimator {
    WTF_MAKE_FAST_ALLOCATED; WTF_MAKE_NONCOPYABLE(ScrollAnimator);
public:
    static PassOwnPtr<ScrollAnimator> create(ScrollableArea*);

    virtual ~ScrollAnimator();

    // Computes a scroll destination for the given parameters.  Returns false if
    // already at the destination.  Otherwise, starts scrolling towards the
    // destination and returns true.  Scrolling may be immediate or animated.
    // The base class implementation always scrolls immediately, never animates.
    virtual bool scroll(ScrollbarOrientation, ScrollGranularity, float step, float delta);

    virtual void scrollToOffsetWithoutAnimation(const FloatPoint&);

    ScrollableArea* scrollableArea() const { return m_scrollableArea; }

    virtual void setIsActive() { }

    virtual bool handleWheelEvent(const PlatformWheelEvent&);

    void setCurrentPosition(const FloatPoint&);
    FloatPoint currentPosition() const;

    virtual void cancelAnimations() { }
    virtual void serviceScrollAnimations() { }

    virtual void mouseEnteredContentArea() const { }
    virtual void mouseExitedContentArea() const { }
    virtual void mouseMovedInContentArea() const { }
    virtual void mouseEnteredScrollbar(Scrollbar*) const { }
    virtual void mouseExitedScrollbar(Scrollbar*) const { }
    virtual void contentsResized() const { }

    virtual void contentAreaDidShow() const { }
    virtual void contentAreaDidHide() const { }

    virtual void finishCurrentScrollAnimations() { }

    virtual void didAddVerticalScrollbar(Scrollbar*) { }
    virtual void willRemoveVerticalScrollbar(Scrollbar*) { }
    virtual void didAddHorizontalScrollbar(Scrollbar*) { }
    virtual void willRemoveHorizontalScrollbar(Scrollbar*) { }

    virtual bool shouldScrollbarParticipateInHitTesting(Scrollbar*) { return true; }

    virtual void notifyContentAreaScrolled(const FloatSize&) { }

protected:
    explicit ScrollAnimator(ScrollableArea*);

    virtual void notifyPositionChanged();

    ScrollableArea* m_scrollableArea;
    float m_currentPosX; // We avoid using a FloatPoint in order to reduce
    float m_currentPosY; // subclass code complexity.

private:
    float clampScrollPosition(ScrollbarOrientation, float);
};

} // namespace blink

#endif  // SKY_ENGINE_PLATFORM_SCROLL_SCROLLANIMATOR_H_