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 * Copyright (c) 2010, Google Inc. All rights reserved.
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 * 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.
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 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
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 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
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 */

#ifndef ScrollAnimator_h
#define ScrollAnimator_h

#include "FloatSize.h"
#include "PlatformWheelEvent.h"
#include "ScrollTypes.h"
#include <wtf/FastAllocBase.h>
#include <wtf/Forward.h>

namespace WebCore {

class FloatPoint;
class ScrollableArea;
class Scrollbar;

class ScrollAnimator {
    WTF_MAKE_FAST_ALLOCATED;
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 multiplier);

    virtual void scrollToOffsetWithoutAnimation(const FloatPoint&);

    ScrollableArea* scrollableArea() const { return m_scrollableArea; }

    virtual void setIsActive() { }

    virtual bool handleWheelEvent(const PlatformWheelEvent&);

#if PLATFORM(MAC)
    virtual void handleWheelEventPhase(PlatformWheelEventPhase) { }
#endif

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

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

    virtual void contentAreaWillPaint() const { }
    virtual void mouseEnteredContentArea() const { }
    virtual void mouseExitedContentArea() const { }
    virtual void mouseMovedInContentArea() const { }
    virtual void mouseEnteredScrollbar(Scrollbar*) const { }
    virtual void mouseExitedScrollbar(Scrollbar*) const { }
    virtual void willStartLiveResize() { }
    virtual void contentsResized() const { }
    virtual void willEndLiveResize() { }
    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& delta) { UNUSED_PARAM(delta); }

    virtual bool isRubberBandInProgress() const { return false; }

protected:
    explicit ScrollAnimator(ScrollableArea*);

    virtual void notifyPositionChanged(const FloatSize& delta);

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

} // namespace WebCore

#endif // ScrollAnimator_h
