/*

 * 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

 * OWNER OR 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 CONTRACT, STRICT LIABILITY, OR TORT

 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 */

#include "config.h"

#include "DragScrollTimer.h"

#include "FrameView.h"

using namespace WebCore;

namespace WebKit {

// Computes the distance from a point outside a rect to the nearest edge of the rect.

static IntSize distanceToRect(const IntPoint& point, const IntRect& rect)

{

    int dx = 0, dy = 0;

    if (point.x() < rect.x())

        dx = point.x() - rect.x();

    else if (rect.right() < point.x())

        dx = point.x() - rect.right();

    if (point.y() < rect.y())

        dy = point.y() - rect.y();

    else if (rect.bottom() < point.y())

        dy = point.y() - rect.bottom();

    return IntSize(dx, dy);

}

DragScrollTimer::DragScrollTimer()

    : m_timer(this, &DragScrollTimer::fired)

    , m_view(0)

    , m_scrolling(false)

{

}

DragScrollTimer::~DragScrollTimer()

{

    // We do this for detecting dead object earlier

    stop(); 

}

void DragScrollTimer::stop()

{

    m_timer.stop();

    m_view = 0;

    m_scrolling = false;

}

void DragScrollTimer::scroll()

{

    m_view->scrollBy(m_lastDistance);

    m_scrolling = true;

}

void DragScrollTimer::update()

{

    if (shouldScroll())

        scroll();

    else

        stop();

}

void DragScrollTimer::triggerScroll(FrameView* view, const WebPoint& location)

{

    if (!view)

        return;

    // Approximates Safari

    static const double scrollStartDelay = 0.2;

    m_view = view;

    m_lastDistance = scrollDistanceFor(view, location);

    if (m_scrolling)

        update();

    else if (shouldScroll() && !m_timer.isActive())

        m_timer.startOneShot(scrollStartDelay);

}

IntSize DragScrollTimer::scrollDistanceFor(FrameView* view, const WebPoint& location) const

{

    static const int scrollMargin = 30;

    IntRect bounds(0, 0, view->visibleWidth(), view->visibleHeight());

    if (!bounds.contains(location))

        return IntSize(0, 0); // The location is outside the border belt.

    bounds.setY(bounds.y() + scrollMargin);

    bounds.setHeight(bounds.height() - scrollMargin * 2);

    bounds.setX(bounds.x() + scrollMargin);

    bounds.setWidth(bounds.width() - scrollMargin * 2);

    if (bounds.contains(location))

        return IntSize(0, 0); // The location is inside the border belt.

    // The location is over the border belt.

    return distanceToRect(location, bounds);

}

} // namespace WebKit