Adapt and reland old position sticky implementation

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

Index: third_party/WebKit/Source/core/page/scrolling/StickyPositionViewportConstraints.h
diff --git a/third_party/WebKit/Source/core/page/scrolling/StickyPositionViewportConstraints.h b/third_party/WebKit/Source/core/page/scrolling/StickyPositionViewportConstraints.h
new file mode 100644
index 0000000000000000000000000000000000000000..1508d210ea6ae3d0a3300818e471c276dc966196
--- /dev/null
+++ b/third_party/WebKit/Source/core/page/scrolling/StickyPositionViewportConstraints.h
@@ -0,0 +1,72 @@
+// 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 StickyPositionViewportConstraints_h
+#define StickyPositionViewportConstraints_h
+
+#include "core/page/scrolling/ViewportConstraints.h"
+
+namespace blink {
+
+class StickyPositionViewportConstraints final : public ViewportConstraints {

[chrishtr, 2016/01/30 01:49:03]

On further reflection, StickyPositionScrollingConstraints is more accurate.

[flackr, 2016/02/22 22:55:23]

Done.

+public:
+    StickyPositionViewportConstraints()
+        : m_leftOffset(0)
+        , m_rightOffset(0)
+        , m_topOffset(0)
+        , m_bottomOffset(0)
+    { }
+
+    StickyPositionViewportConstraints(const StickyPositionViewportConstraints& other)
+        : ViewportConstraints(other)
+        , m_leftOffset(other.m_leftOffset)
+        , m_rightOffset(other.m_rightOffset)
+        , m_topOffset(other.m_topOffset)
+        , m_bottomOffset(other.m_bottomOffset)
+        , m_absoluteContainingBlockRect(other.m_absoluteContainingBlockRect)
+        , m_absoluteStickyBoxRect(other.m_absoluteStickyBoxRect)
+    { }
+
+    FloatSize computeStickyOffset(const FloatRect& viewportRect) const;
+
+    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 setAbsoluteContainingBlockRect(const FloatRect& rect) { m_absoluteContainingBlockRect = rect; }

[chrishtr, 2016/01/30 01:49:03]

setScrollContainerRelativeContainingBlockRect

[flackr, 2016/02/22 22:55:23]

Done.

+
+    void setAbsoluteStickyBoxRect(const FloatRect& rect) { m_absoluteStickyBoxRect = rect; }

[chrishtr, 2016/01/30 01:49:03]

setScrollContainerRelativeStickyBoxRect

[flackr, 2016/02/22 22:55:23]

Done.

+
+    bool operator==(const StickyPositionViewportConstraints& other) const
+    {
+        return m_leftOffset == other.m_leftOffset
+            && m_rightOffset == other.m_rightOffset
+            && m_topOffset == other.m_topOffset
+            && m_bottomOffset == other.m_bottomOffset
+            && m_absoluteContainingBlockRect == other.m_absoluteContainingBlockRect
+            && m_absoluteStickyBoxRect == other.m_absoluteStickyBoxRect;
+    }
+
+    bool operator!=(const StickyPositionViewportConstraints& other) const { return !(*this == other); }
+
+private:
+    ConstraintType constraintType() const override { return StickyPositionConstraint; }
+
+    float m_leftOffset;
+    float m_rightOffset;
+    float m_topOffset;
+    float m_bottomOffset;
+    FloatRect m_absoluteContainingBlockRect;
+    FloatRect m_absoluteStickyBoxRect;
+};
+
+} // namespace blink
+
+#endif // StickyPositionViewportConstraints_h