position:sticky should stick for the enclosing overflow ancestor

Source/core/rendering/RenderBoxModelObject.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  *           (C) 2005, 2006 Samuel Weinig (sam.weinig@gmail.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Google Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 301 matching lines @@
             if (current->isRenderNamedFlowThread())
                 referencePoint = toRenderNamedFlowThread(current)->adjustedPositionRelativeToOffsetParent(*this, referencePoint);
             else if (offsetParent->isBox() && offsetParent->isBody() && !offsetParent->isPositioned())
                 referencePoint.moveBy(toRenderBox(offsetParent)->topLeftLocation());
         }
     }
 
     return referencePoint;
 }
 
-void RenderBoxModelObject::computeStickyPositionConstraints(StickyPositionViewportConstraints& constraints, const FloatRect& viewportRect) const
+void RenderBoxModelObject::computeStickyPositionConstraints(StickyPositionViewportConstraints& constraints, const FloatRect& constrainingRect) const
 {
     RenderBlock* containingBlock = this->containingBlock();
 
     LayoutRect containerContentRect = containingBlock->contentBoxRect();
     LayoutUnit maxWidth = containingBlock->availableLogicalWidth();
 
     // Sticky positioned element ignore any override logical width on the containing block (as they don't call
     // containingBlockLogicalWidthForContent). It's unclear whether this is totally fine.
     LayoutBoxExtent minMargin(minimumValueForLength(style()->marginTop(), maxWidth),
         minimumValueForLength(style()->marginRight(), maxWidth),
         minimumValueForLength(style()->marginBottom(), maxWidth),
         minimumValueForLength(style()->marginLeft(), maxWidth));
 
     // Compute the container-relative area within which the sticky element is allowed to move.
     containerContentRect.contract(minMargin);
     // Map to the view to avoid including page scale factor.
     constraints.setAbsoluteContainingBlockRect(containingBlock->localToContainerQuad(FloatRect(containerContentRect), view()).boundingBox());
 
     LayoutRect stickyBoxRect = frameRectForStickyPositioning();
     LayoutRect flippedStickyBoxRect = stickyBoxRect;
     containingBlock->flipForWritingMode(flippedStickyBoxRect);
     LayoutPoint stickyLocation = flippedStickyBoxRect.location();
 
     // FIXME: sucks to call localToAbsolute again, but we can't just offset from the previously computed rect if there are transforms.
     // Map to the view to avoid including page scale factor.
     FloatRect absContainerFrame = containingBlock->localToContainerQuad(FloatRect(FloatPoint(), containingBlock->size()), view()).boundingBox();
 
+    if (containingBlock->hasOverflowClip()) {
+        IntSize scrollOffset = containingBlock->layer()->scrollableArea()->adjustedScrollOffset();
+        stickyLocation -= scrollOffset;
+    }
+
     // We can't call localToAbsolute on |this| because that will recur. FIXME: For now, assume that |this| is not transformed.
     FloatRect absoluteStickyBoxRect(absContainerFrame.location() + stickyLocation, flippedStickyBoxRect.size());
     constraints.setAbsoluteStickyBoxRect(absoluteStickyBoxRect);
 
     if (!style()->left().isAuto()) {
-        constraints.setLeftOffset(valueForLength(style()->left(), viewportRect.width()));
+        constraints.setLeftOffset(valueForLength(style()->left(), constrainingRect.width()));
         constraints.addAnchorEdge(ViewportConstraints::AnchorEdgeLeft);
     }
 
     if (!style()->right().isAuto()) {
-        constraints.setRightOffset(valueForLength(style()->right(), viewportRect.width()));
+        constraints.setRightOffset(valueForLength(style()->right(), constrainingRect.width()));
         constraints.addAnchorEdge(ViewportConstraints::AnchorEdgeRight);
     }
 
     if (!style()->top().isAuto()) {
-        constraints.setTopOffset(valueForLength(style()->top(), viewportRect.height()));
+        constraints.setTopOffset(valueForLength(style()->top(), constrainingRect.height()));
         constraints.addAnchorEdge(ViewportConstraints::AnchorEdgeTop);
     }
 
     if (!style()->bottom().isAuto()) {
-        constraints.setBottomOffset(valueForLength(style()->bottom(), viewportRect.height()));
+        constraints.setBottomOffset(valueForLength(style()->bottom(), constrainingRect.height() ));
         constraints.addAnchorEdge(ViewportConstraints::AnchorEdgeBottom);
     }
 }
 
 LayoutSize RenderBoxModelObject::stickyPositionOffset() const
 {
-    LayoutRect viewportRect = view()->frameView()->viewportConstrainedVisibleContentRect();
+    FloatRect constrainingRect;
+
+    ASSERT(hasLayer());
+    RenderLayer* enclosingClippingLayer = layer()->enclosingOverflowClipLayer(ExcludeSelf);
+    if (enclosingClippingLayer) {
+        RenderBox* enclosingClippingBox = toRenderBox(enclosingClippingLayer->renderer());
+        LayoutRect clipRect = enclosingClippingBox->overflowClipRect(LayoutPoint(), 0); // FIXME: make this work in regions.
+        constrainingRect = enclosingClippingBox->localToContainerQuad(FloatRect(clipRect), view()).boundingBox();
+    } else {
+        LayoutRect viewportRect = view()->frameView()->viewportConstrainedVisibleContentRect();
+        constrainingRect = viewportRect;
+    }
 
     StickyPositionViewportConstraints constraints;
-    computeStickyPositionConstraints(constraints, viewportRect);
+    computeStickyPositionConstraints(constraints, constrainingRect);
 
     // The sticky offset is physical, so we can just return the delta computed in absolute coords (though it may be wrong with transforms).
-    return LayoutSize(constraints.computeStickyOffset(viewportRect));
+    return LayoutSize(constraints.computeStickyOffset(constrainingRect));
 }
 
 LayoutSize RenderBoxModelObject::offsetForInFlowPosition() const
 {
     if (isRelPositioned())
         return relativePositionOffset();
 
     if (isStickyPositioned())
         return stickyPositionOffset();
 
@@ skipping 2420 matching lines @@
     ASSERT(!beforeChild || toBoxModelObject == beforeChild->parent());
     for (RenderObject* child = startChild; child && child != endChild; ) {
         // Save our next sibling as moveChildTo will clear it.
         RenderObject* nextSibling = child->nextSibling();
         moveChildTo(toBoxModelObject, child, beforeChild, fullRemoveInsert);
         child = nextSibling;
     }
 }
 
 } // namespace WebCore