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      1 /*
      2  * Copyright (C) 2012 Apple Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  * 1. Redistributions of source code must retain the above copyright
      8  *    notice, this list of conditions and the following disclaimer.
      9  * 2. Redistributions in binary form must reproduce the above copyright
     10  *    notice, this list of conditions and the following disclaimer in the
     11  *    documentation and/or other materials provided with the distribution.
     12  *
     13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS''
     14  * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
     15  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     16  * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS
     17  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     18  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     19  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     20  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     21  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     22  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
     23  * THE POSSIBILITY OF SUCH DAMAGE.
     24  */
     25 
     26 #include "config.h"
     27 #include "core/page/scrolling/ScrollingConstraints.h"
     28 
     29 namespace WebCore {
     30 
     31 FloatPoint FixedPositionViewportConstraints::layerPositionForViewportRect(const FloatRect& viewportRect) const
     32 {
     33     FloatSize offset;
     34 
     35     if (hasAnchorEdge(AnchorEdgeLeft))
     36         offset.setWidth(viewportRect.x() - m_viewportRectAtLastLayout.x());
     37     else if (hasAnchorEdge(AnchorEdgeRight))
     38         offset.setWidth(viewportRect.maxX() - m_viewportRectAtLastLayout.maxX());
     39 
     40     if (hasAnchorEdge(AnchorEdgeTop))
     41         offset.setHeight(viewportRect.y() - m_viewportRectAtLastLayout.y());
     42     else if (hasAnchorEdge(AnchorEdgeBottom))
     43         offset.setHeight(viewportRect.maxY() - m_viewportRectAtLastLayout.maxY());
     44 
     45     return m_layerPositionAtLastLayout + offset;
     46 }
     47 
     48 FloatSize StickyPositionViewportConstraints::computeStickyOffset(const FloatRect& viewportRect) const
     49 {
     50     FloatRect boxRect = m_absoluteStickyBoxRect;
     51 
     52     if (hasAnchorEdge(AnchorEdgeRight)) {
     53         float rightLimit = viewportRect.maxX() - m_rightOffset;
     54         float rightDelta = std::min<float>(0, rightLimit - m_absoluteStickyBoxRect.maxX());
     55         float availableSpace = std::min<float>(0, m_absoluteContainingBlockRect.x() - m_absoluteStickyBoxRect.x());
     56         if (rightDelta < availableSpace)
     57             rightDelta = availableSpace;
     58 
     59         boxRect.move(rightDelta, 0);
     60     }
     61 
     62     if (hasAnchorEdge(AnchorEdgeLeft)) {
     63         float leftLimit = viewportRect.x() + m_leftOffset;
     64         float leftDelta = std::max<float>(0, leftLimit - m_absoluteStickyBoxRect.x());
     65         float availableSpace = std::max<float>(0, m_absoluteContainingBlockRect.maxX() - m_absoluteStickyBoxRect.maxX());
     66         if (leftDelta > availableSpace)
     67             leftDelta = availableSpace;
     68 
     69         boxRect.move(leftDelta, 0);
     70     }
     71 
     72     if (hasAnchorEdge(AnchorEdgeBottom)) {
     73         float bottomLimit = viewportRect.maxY() - m_bottomOffset;
     74         float bottomDelta = std::min<float>(0, bottomLimit - m_absoluteStickyBoxRect.maxY());
     75         float availableSpace = std::min<float>(0, m_absoluteContainingBlockRect.y() - m_absoluteStickyBoxRect.y());
     76         if (bottomDelta < availableSpace)
     77             bottomDelta = availableSpace;
     78 
     79         boxRect.move(0, bottomDelta);
     80     }
     81 
     82     if (hasAnchorEdge(AnchorEdgeTop)) {
     83         float topLimit = viewportRect.y() + m_topOffset;
     84         float topDelta = std::max<float>(0, topLimit - m_absoluteStickyBoxRect.y());
     85         float availableSpace = std::max<float>(0, m_absoluteContainingBlockRect.maxY() - m_absoluteStickyBoxRect.maxY());
     86         if (topDelta > availableSpace)
     87             topDelta = availableSpace;
     88 
     89         boxRect.move(0, topDelta);
     90     }
     91 
     92     return boxRect.location() - m_absoluteStickyBoxRect.location();
     93 }
     94 
     95 FloatPoint StickyPositionViewportConstraints::layerPositionForViewportRect(const FloatRect& viewportRect) const
     96 {
     97     FloatSize offset = computeStickyOffset(viewportRect);
     98     return m_layerPositionAtLastLayout + offset - m_stickyOffsetAtLastLayout;
     99 }
    100 
    101 } // namespace WebCore
    102