DragScrollTimer.h   [plain text]

/*
 * Copyright (C) 2010 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
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND 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 THE COPYRIGHT
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 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 */

#ifndef DragScrollTimer_h
#define DragScrollTimer_h

#include "IntSize.h"
#include "Timer.h"
#include "platform/WebPoint.h"

namespace WebCore { class FrameView; }

namespace WebKit {

//
// Encapsulating a timer and associated state management for
// scroll-on-drag behaviour.
//
class DragScrollTimer {
public:
    DragScrollTimer();
    ~DragScrollTimer();

    void fired(WebCore::Timer<DragScrollTimer>*) { update(); }
    void triggerScroll(WebCore::FrameView*, const WebPoint&);
    void stop();

private:
    void scroll();
    void update();
    WebCore::IntSize scrollDistanceFor(WebCore::FrameView*, const WebPoint&) const;
    bool shouldScroll() const { return !m_lastDistance.isZero(); }

    WebCore::Timer<DragScrollTimer> m_timer;
    WebCore::FrameView* m_view;
    WebCore::IntSize m_lastDistance;
    bool m_scrolling;
};

} // namespace WebKit

#endif