SVG root viewport clip in paint property tree

third_party/WebKit/Source/core/paint/PaintInvalidator.cpp

Index: third_party/WebKit/Source/core/paint/PaintInvalidator.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintInvalidator.cpp b/third_party/WebKit/Source/core/paint/PaintInvalidator.cpp
index d30a142cd29bc6525cb085b8b325e6d151538602..c4254a8d90a97b66aae2cfe310f83c63a119a312 100644
--- a/third_party/WebKit/Source/core/paint/PaintInvalidator.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintInvalidator.cpp
@@ -20,12 +20,20 @@
 
 namespace blink {
 
-static void slowMapToVisualRectInAncestorSpace(const LayoutObject& object, const LayoutBoxModelObject& ancestor, LayoutRect& rect)
+static LayoutRect slowMapToVisualRectInAncestorSpace(const LayoutObject& object, const LayoutBoxModelObject& ancestor, const FloatRect& rect)
 {
+    if (object.isSVG() && !object.isSVGRoot()) {
+        LayoutRect result;
+        SVGLayoutSupport::mapToVisualRectInAncestorSpace(object, &ancestor, rect, result);

[pdr., 2016/09/14 22:42:39]

If we override this in all SVG subclasses, will this special-case be needed? I'd
prefer if we could rely on this working through the
object.mapToVisualRectInAncestorSpace call below, but I'm not sure if it is
possible. We already override LayoutSVGBlock::mapToVisualRectInAncestorSpace, do
we just need to override it in LayoutSVGModelObject, LayoutSVGBlock, and
LayoutSVGInline too?

[Xianzhu, 2016/09/14 23:35:31]

We didn't override mapToVisualRectInAncestorSpace in other SVG objects because
they were never called. SVGLayoutSupport::mapToVisualRectInAncestorSpace() was
used by only LayoutSVGBlock::mapToVisualRectInAncestorSpace() (which may be
called from HTML descendants) and
SVGLayoutSupport::clippedOverflowRectForPaintInvalidation(). Its input rect is a
FloatRect so if we match it to LayoutObject::mapToVisualRectInAncestorSpace() we
may lose accuracy.

I would keep this special case for now because this code is temporary for
filters before paint property tree supports filters.

+        return result;
+    }
+
+    LayoutRect result(rect);
     if (object.isLayoutView())
-        toLayoutView(object).mapToVisualRectInAncestorSpace(&ancestor, rect, InputIsInFrameCoordinates, DefaultVisualRectFlags);
+        toLayoutView(object).mapToVisualRectInAncestorSpace(&ancestor, result, InputIsInFrameCoordinates, DefaultVisualRectFlags);
     else
-        object.mapToVisualRectInAncestorSpace(&ancestor, rect);
+        object.mapToVisualRectInAncestorSpace(&ancestor, result);
+    return result;
 }
 
 // TODO(wangxianzhu): Combine this into PaintInvalidator::mapLocalRectToPaintInvalidationBacking() when removing PaintInvalidationState.
@@ -41,8 +49,7 @@ static LayoutRect mapLocalRectToPaintInvalidationBacking(GeometryMapper& geometr
 
     LayoutRect result;
     if (context.forcedSubtreeInvalidationFlags & PaintInvalidatorContext::ForcedSubtreeSlowPathRect) {
-        result = LayoutRect(rect);
-        slowMapToVisualRectInAncestorSpace(object, *context.paintInvalidationContainer, result);
+        result = slowMapToVisualRectInAncestorSpace(object, *context.paintInvalidationContainer, rect);
     } else if (object == context.paintInvalidationContainer) {
         result = LayoutRect(rect);
     } else {