Bug 869611 - Stop reflowing in nsSVGPathGeometryFrame::NotifySVGChanged for ancestor transform changes. r=dholbert

content/svg/content/src/nsSVGPathGeometryElement.cpp

@@ -4,6 +4,7 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #include "nsSVGPathGeometryElement.h"
+#include "nsSVGLength2.h"
 
 //----------------------------------------------------------------------
 // Implementation
@@ -27,6 +28,19 @@ nsSVGPathGeometryElement::AttributeDefinesGeometry(const nsIAtom *aName)
   return false;
 }
 
+bool
+nsSVGPathGeometryElement::GeometryDependsOnCoordCtx()
+{
+  // Check the nsSVGLength2 attribute
+  LengthAttributesInfo info = const_cast<nsSVGPathGeometryElement*>(this)->GetLengthInfo();
+  for (uint32_t i = 0; i < info.mLengthCount; i++) {
+    if (info.mLengths[i].GetSpecifiedUnitType() == nsIDOMSVGLength::SVG_LENGTHTYPE_PERCENTAGE) {
+      return true;
+    }   
+  }
+  return false;
+}
+
 bool
 nsSVGPathGeometryElement::IsMarkable()
 {

content/svg/content/src/nsSVGPathGeometryElement.h

@@ -27,6 +27,18 @@ public:
   nsSVGPathGeometryElement(already_AddRefed<nsINodeInfo> aNodeInfo);
 
   virtual bool AttributeDefinesGeometry(const nsIAtom *aName);
+
+  /**
+   * Returns true if this element's geometry depends on the width or height of its
+   * coordinate context (typically the viewport established by its nearest <svg>
+   * ancestor). In other words, returns true if one of the attributes for which
+   * AttributeDefinesGeometry returns true has a percentage value.
+   *
+   * This could be moved up to a more general class so it can be used for non-leaf
+   * elements, but that would require care and for now there's no need.
+   */
+  bool GeometryDependsOnCoordCtx();
+
   virtual bool IsMarkable();
   virtual void GetMarkPoints(nsTArray<nsSVGMark> *aMarks);
   virtual void ConstructPath(gfxContext *aCtx) = 0;

layout/svg/nsSVGPathGeometryFrame.cpp

@@ -353,12 +353,17 @@ nsSVGPathGeometryFrame::NotifySVGChanged(uint32_t aFlags)
   NS_ABORT_IF_FALSE(aFlags & (TRANSFORM_CHANGED | COORD_CONTEXT_CHANGED),
                     "Invalidation logic may need adjusting");
 
-  // Ancestor changes can't affect how we render from the perspective of
-  // any rendering observers that we may have, so we don't need to
-  // invalidate them. We also don't need to invalidate ourself, since our
-  // changed ancestor will have invalidated its entire area, which includes
-  // our area.
-  nsSVGUtils::ScheduleReflowSVG(this);
+  // Changes to our ancestors may affect how we render when we are rendered as
+  // part of our ancestor (specifically, if our coordinate context changes size
+  // and we have percentage lengths defining our geometry, then we need to be
+  // reflowed). However, ancestor changes cannot affect how we render when we
+  // are rendered as part of any rendering observers that we may have.
+  // Therefore no need to notify rendering observers here.
+
+  if ((aFlags & COORD_CONTEXT_CHANGED) &&
+      static_cast<nsSVGPathGeometryElement*>(mContent)->GeometryDependsOnCoordCtx()) {
+    nsSVGUtils::ScheduleReflowSVG(this);
+  }
 }
 
 SVGBBox