Adapt and reland old position sticky implementation

third_party/WebKit/Source/core/page/scrolling/StickyPositionScrollingConstraints.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef StickyPositionScrollingConstraints_h
+#define StickyPositionScrollingConstraints_h
+
+#include "platform/geometry/FloatRect.h"
+
+namespace blink {
+
+class StickyPositionScrollingConstraints final {
+public:
+    enum AnchorEdgeFlags {
+        AnchorEdgeLeft = 1 << 0,
+        AnchorEdgeRight = 1 << 1,
+        AnchorEdgeTop = 1 << 2,
+        AnchorEdgeBottom = 1 << 3
+    };
+    typedef unsigned AnchorEdges;
+
+    StickyPositionScrollingConstraints()
+        : m_leftOffset(0)
+        , m_rightOffset(0)
+        , m_topOffset(0)
+        , m_bottomOffset(0)
+    { }
+
+    StickyPositionScrollingConstraints(const StickyPositionScrollingConstraints& other)
+        : m_anchorEdges(0)
+        , m_leftOffset(other.m_leftOffset)
+        , m_rightOffset(other.m_rightOffset)
+        , m_topOffset(other.m_topOffset)
+        , m_bottomOffset(other.m_bottomOffset)
+        , m_scrollContainerRelativeContainingBlockRect(other.m_scrollContainerRelativeContainingBlockRect)
+        , m_scrollContainerRelativeStickyBoxRect(other.m_scrollContainerRelativeStickyBoxRect)
+    { }
+
+    FloatSize computeStickyOffset(const FloatRect& viewportRect) const;
+
+    AnchorEdges anchorEdges() const { return m_anchorEdges; }
+    bool hasAnchorEdge(AnchorEdgeFlags flag) const { return m_anchorEdges & flag; }
+    void addAnchorEdge(AnchorEdgeFlags edgeFlag) { m_anchorEdges |= edgeFlag; }
+    void setAnchorEdges(AnchorEdges edges) { m_anchorEdges = edges; }
+
+    float leftOffset() const { return m_leftOffset; }
+    float rightOffset() const { return m_rightOffset; }
+    float topOffset() const { return m_topOffset; }
+    float bottomOffset() const { return m_bottomOffset; }
+
+    void setLeftOffset(float offset) { m_leftOffset = offset; }
+    void setRightOffset(float offset) { m_rightOffset = offset; }
+    void setTopOffset(float offset) { m_topOffset = offset; }
+    void setBottomOffset(float offset) { m_bottomOffset = offset; }
+
+    void setScrollContainerRelativeContainingBlockRect(const FloatRect& rect) { m_scrollContainerRelativeContainingBlockRect = rect; }
+
+    void setScrollContainerRelativeStickyBoxRect(const FloatRect& rect) { m_scrollContainerRelativeStickyBoxRect = rect; }
+
+    bool operator==(const StickyPositionScrollingConstraints& other) const
+    {
+        return m_leftOffset == other.m_leftOffset
+            && m_rightOffset == other.m_rightOffset
+            && m_topOffset == other.m_topOffset
+            && m_bottomOffset == other.m_bottomOffset
+            && m_scrollContainerRelativeContainingBlockRect == other.m_scrollContainerRelativeContainingBlockRect
+            && m_scrollContainerRelativeStickyBoxRect == other.m_scrollContainerRelativeStickyBoxRect;
+    }
+
+    bool operator!=(const StickyPositionScrollingConstraints& other) const { return !(*this == other); }
+
+private:
+    AnchorEdges m_anchorEdges;
+    float m_leftOffset;
+    float m_rightOffset;
+    float m_topOffset;
+    float m_bottomOffset;
+    FloatRect m_scrollContainerRelativeContainingBlockRect;
+    FloatRect m_scrollContainerRelativeStickyBoxRect;
+};
+
+} // namespace blink
+
+#endif // StickyPositionScrollingConstraints_h