Source/WebCore/page/scrolling/ScrollingTreeGestureState.h

/*
 * Copyright (C) 2020 Apple 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:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 */

#pragma once

#if ENABLE(ASYNC_SCROLLING)

#include "ScrollTypes.h"
#include <wtf/Markable.h>
#include <wtf/Optional.h>

namespace WebCore {

class PlatformWheelEvent;
class ScrollingTree;

// This class tracks state related to MayBegin, Begin, Ended and Canceled wheel events, which
// should propagate to the main thread in order to update overlay scrollbars.
class ScrollingTreeGestureState {
public:
    ScrollingTreeGestureState(ScrollingTree&);

    void receivedWheelEvent(const PlatformWheelEvent&);

    bool handleGestureCancel(const PlatformWheelEvent&);

    void nodeDidHandleEvent(ScrollingNodeID, const PlatformWheelEvent&);
    
private:
    void clearAllNodes();

    ScrollingTree& m_scrollingTree;
    Markable<ScrollingNodeID, IntegralMarkableTraits<ScrollingNodeID, 0>> m_mayBeginNodeID;
    Markable<ScrollingNodeID, IntegralMarkableTraits<ScrollingNodeID, 0>> m_activeNodeID;
};

}

#endif // ENABLE(ASYNC_SCROLLING)