Implement position: sticky updates on compositor

third_party/WebKit/public/platform/WebLayerStickyPositionConstraint.h

+/*
+ * Copyright (C) 2013 Google 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 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 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 WebLayerStickyPositionConstraint_h
+#define WebLayerStickyPositionConstraint_h
+
+namespace blink {
+
+// TODO(flackr): Combine with WebLayerPositionConstraint.
+struct WebLayerStickyPositionConstraint {
+    // True if the layer is sticky.
+    bool isSticky         : 1;
+
+    // For each edge, true if the layer should stick to that edge of its
+    // ancestor scroller (or the viewport).
+    bool isAnchoredLeft   : 1;
+    bool isAnchoredRight  : 1;
+    bool isAnchoredTop    : 1;
+    bool isAnchoredBottom : 1;
+
+    // For each edge, when the anchored bit above is set this gives the distance
+    // to keep the element from that edge of the ancestor scroller or viewport.
+    float leftOffset;
+    float rightOffset;
+    float topOffset;
+    float bottomOffset;
+
+    // The layout rectangle of the sticky element before it has been shifted
+    // to stick.
+    WebRect scrollContainerRelativeStickyBoxRect;
+
+    // The layout rectangle of the containing block edges which this sticky
+    // element should not be shifted beyond.
+    WebRect scrollContainerRelativeContainingBlockRect;
+
+    WebLayerStickyPositionConstraint()
+        : isSticky(false)
+        , isAnchoredLeft(false)
+        , isAnchoredRight(false)
+        , isAnchoredTop(false)
+        , isAnchoredBottom(false)
+        , leftOffset(0.f)
+        , rightOffset(0.f)
+        , topOffset(0.f)
+        , bottomOffset(0.f)
+    {
+    }
+};
+
+} // namespace blink
+
+#endif // WebLayerStickyPositionConstraint_h
+