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/*
* Copyright (C) 2014 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
* 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.
*/
#ifndef AxisScrollSnapOffsets_h
#define AxisScrollSnapOffsets_h
#if ENABLE(CSS_SCROLL_SNAP)
#include "ScrollTypes.h"
#include <wtf/PassOwnPtr.h>
#include <wtf/Vector.h>
namespace WebCore {
class HTMLElement;
class RenderBox;
class RenderStyle;
class ScrollableArea;
void updateSnapOffsetsForScrollableArea(ScrollableArea&, HTMLElement& scrollingElement, const RenderBox& scrollingElementBox, const RenderStyle& scrollingElementStyle);
// closestSnapOffset is a templated function that takes in a Vector representing snap offsets as LayoutTypes (e.g. LayoutUnit or float) and
// as well as a VelocityType indicating the velocity (e.g. float, CGFloat, etc.) This function is templated because the UI process will now
// use pixel snapped floats to represent snap offsets rather than LayoutUnits.
template <typename LayoutType, typename VelocityType>
LayoutType closestSnapOffset(const Vector<LayoutType>& snapOffsets, LayoutType scrollDestination, VelocityType velocity)
{
ASSERT(snapOffsets.size());
if (scrollDestination <= snapOffsets.first())
return snapOffsets.first();
if (scrollDestination >= snapOffsets.last())
return snapOffsets.last();
size_t lowerIndex = 0;
size_t upperIndex = snapOffsets.size() - 1;
while (lowerIndex < upperIndex - 1) {
size_t middleIndex = (lowerIndex + upperIndex) / 2;
if (scrollDestination < snapOffsets[middleIndex])
upperIndex = middleIndex;
else if (scrollDestination > snapOffsets[middleIndex])
lowerIndex = middleIndex;
else {
upperIndex = middleIndex;
lowerIndex = middleIndex;
break;
}
}
LayoutType lowerSnapPosition = snapOffsets[lowerIndex];
LayoutType upperSnapPosition = snapOffsets[upperIndex];
// Nonzero velocity indicates a flick gesture. Even if another snap point is closer, snap to the one in the direction of the flick gesture.
if (velocity)
return velocity < 0 ? lowerSnapPosition : upperSnapPosition;
bool isCloserToLowerSnapPosition = scrollDestination - lowerSnapPosition <= upperSnapPosition - scrollDestination;
return isCloserToLowerSnapPosition ? lowerSnapPosition : upperSnapPosition;
}
} // namespace WebCore
#endif // CSS_SCROLL_SNAP
#endif // AxisScrollSnapOffsets_h
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