Support edge-inclusive intersections in mapToVisibleRectInAncestorSpace

third_party/WebKit/Source/core/layout/LayoutInline.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009 Apple 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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 1041 matching lines @@
 
 LayoutRect LayoutInline::clippedOverflowRect(const LayoutBoxModelObject* paintInvalidationContainer, const PaintInvalidationState* paintInvalidationState) const
 {
     if (style()->visibility() != VISIBLE)
         return LayoutRect();
 
     LayoutRect overflowRect(visualOverflowRect());
     if (overflowRect.isEmpty())
         return overflowRect;
 
-    mapToVisibleRectInAncestorSpace(paintInvalidationContainer, overflowRect, paintInvalidationState);
+    mapToVisibleRectInAncestorSpace(paintInvalidationContainer, overflowRect, paintInvalidationState, false);
     return overflowRect;
 }
 
 LayoutRect LayoutInline::visualOverflowRect() const
 {
     LayoutRect overflowRect = linesVisualOverflowBoundingBox();
     LayoutUnit outlineOutset(style()->outlineOutsetExtent());
     if (outlineOutset) {
         Vector<LayoutRect> rects;
         // We have already included outline extents of line boxes in linesVisualOverflowBoundingBox(),
         // so the following just add outline rects for children and continuations.
         addOutlineRectsForChildrenAndContinuations(rects, LayoutPoint(), outlineRectsShouldIncludeBlockVisualOverflow());
         if (!rects.isEmpty()) {
             LayoutRect outlineRect = unionRectEvenIfEmpty(rects);
             outlineRect.inflate(outlineOutset);
             overflowRect.unite(outlineRect);
         }
     }
     return overflowRect;
 }
 
-void LayoutInline::mapToVisibleRectInAncestorSpace(const LayoutBoxModelObject* ancestor, LayoutRect& rect, const PaintInvalidationState* paintInvalidationState) const
+bool LayoutInline::mapToVisibleRectInAncestorSpace(const LayoutBoxModelObject* ancestor, LayoutRect& rect, const PaintInvalidationState* paintInvalidationState, bool edgeInclusive) const

[eae, 2016/03/22 00:13:50]

It's unclear to me why these method would need to be made aware of
edge-inclusion. They're supposed to map the x/y coordinates of the supplied rect
which shouldn't be the same regardless of whether the edge is included or not.
Perhaps I'm missing something here?

Having it return a value is also a bit odd.

[szager1, 2016/03/22 00:55:48]

mapToVisibleRectInAncestorSpace is used by IntersectionObservation to compute
the intersection between to LayoutObject's, and that intersection needs to be
edge-inclusive (required by the spec).  This is the least intrusive way I could
think of for this method to report "the rects intersect, but the intersection is
zero area," as distinct from "the rects do not intersect."

 {
-    if (paintInvalidationState && paintInvalidationState->canMapToAncestor(ancestor)) {
-        paintInvalidationState->mapObjectRectToAncestor(*this, ancestor, rect);
-        return;
-    }
+    if (paintInvalidationState && paintInvalidationState->canMapToAncestor(ancestor))
+        return paintInvalidationState->mapObjectRectToAncestor(*this, ancestor, rect, edgeInclusive);
 
     if (ancestor == this)
-        return;
+        return true;
 
     bool ancestorSkipped;
     LayoutObject* container = this->container(ancestor, &ancestorSkipped);
     if (!container)
-        return;
+        return true;
 
     LayoutPoint topLeft = rect.location();
 
     if (style()->hasInFlowPosition() && layer()) {
         // Apply the in-flow position offset when invalidating a rectangle. The layer
         // is translated, but the layout box isn't, so we need to do this to get the
         // right dirty rect. Since this is called from LayoutObject::setStyle, the relative position
         // flag on the LayoutObject has been cleared, so use the one on the style().
         topLeft += layer()->offsetForInFlowPosition();
     }
 
     // FIXME: We ignore the lightweight clipping rect that controls use, since if |o| is in mid-layout,
     // its controlClipRect will be wrong. For overflow clip we use the values cached by the layer.
     rect.setLocation(topLeft);
     if (container->hasOverflowClip()) {
         LayoutBox* containerBox = toLayoutBox(container);
         containerBox->mapScrollingContentsRectToBoxSpace(rect);
-        if (container != ancestor)
-            containerBox->applyOverflowClip(rect);
-        if (rect.isEmpty())
-            return;
+        if (container != ancestor && !containerBox->applyOverflowClip(rect, edgeInclusive))
+            return false;
     }
 
     if (ancestorSkipped) {
         // If the paintInvalidationContainer is below o, then we need to map the rect into paintInvalidationContainer's coordinates.
         LayoutSize containerOffset = ancestor->offsetFromAncestorContainer(container);
         rect.move(-containerOffset);
-        return;
+        return true;
     }
 
-    container->mapToVisibleRectInAncestorSpace(ancestor, rect, paintInvalidationState);
+    return container->mapToVisibleRectInAncestorSpace(ancestor, rect, paintInvalidationState, edgeInclusive);
 }
 
 LayoutSize LayoutInline::offsetFromContainer(const LayoutObject* container) const
 {
     ASSERT(container == this->container());
 
     LayoutSize offset;
     if (isInFlowPositioned())
         offset += offsetForInFlowPosition();
 
@@ skipping 240 matching lines @@
 
 void LayoutInline::invalidateDisplayItemClients(const LayoutBoxModelObject& paintInvalidationContainer, PaintInvalidationReason invalidationReason) const
 {
     LayoutBoxModelObject::invalidateDisplayItemClients(paintInvalidationContainer, invalidationReason);
 
     for (InlineFlowBox* box = firstLineBox(); box; box = box->nextLineBox())
         paintInvalidationContainer.invalidateDisplayItemClientOnBacking(*box, invalidationReason);
 }
 
 } // namespace blink