Adapt and reland old position sticky implementation

third_party/WebKit/Source/core/page/scrolling/ScrollingConstraints.cpp

-/*
- * Copyright (C) 2012 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.
- */
-
-#include "core/page/scrolling/ScrollingConstraints.h"
-
-namespace blink {
-
-FloatPoint FixedPositionViewportConstraints::layerPositionForViewportRect(const FloatRect& viewportRect) const
-{
-    FloatSize offset;
-
-    if (hasAnchorEdge(AnchorEdgeLeft))
-        offset.setWidth(viewportRect.x() - m_viewportRectAtLastLayout.x());
-    else if (hasAnchorEdge(AnchorEdgeRight))
-        offset.setWidth(viewportRect.maxX() - m_viewportRectAtLastLayout.maxX());
-
-    if (hasAnchorEdge(AnchorEdgeTop))
-        offset.setHeight(viewportRect.y() - m_viewportRectAtLastLayout.y());
-    else if (hasAnchorEdge(AnchorEdgeBottom))
-        offset.setHeight(viewportRect.maxY() - m_viewportRectAtLastLayout.maxY());
-
-    return m_layerPositionAtLastLayout + offset;
-}
-
-} // namespace blink