Fixing bug 272885. Disable rendering of some elements when their width or height is zero. r=tor@acm.org, sr=vladimir@pobox.com, a1.9=mtschrep@gmail.com

gfx/thebes/public/gfxContext.h

@@ -581,4 +581,35 @@ private:
     PRInt32 mFlags;
 };
 
+
+/**
+ * Sentry helper class for functions with multiple return points that need to
+ * call Save() on a gfxContext and have Restore() called automatically on the
+ * gfxContext before they return.
+ */
+class THEBES_API gfxContextAutoSaveRestore
+{
+public:
+  gfxContextAutoSaveRestore() : mContext(nsnull) {}
+
+  gfxContextAutoSaveRestore(gfxContext *aContext) : mContext(aContext) {
+    mContext->Save();
+  }
+
+  ~gfxContextAutoSaveRestore() {
+    if (mContext) {
+      mContext->Restore();
+    }
+  }
+
+  void SetContext(gfxContext *aContext) {
+    NS_ASSERTION(!mContext, "Not going to call Restore() on some context!!!");
+    mContext = aContext;
+    mContext->Save();    
+  }
+
+private:
+  gfxContext *mContext;
+};
+
 #endif /* GFX_CONTEXT_H */

layout/svg/base/src/nsSVGInnerSVGFrame.cpp

@@ -158,37 +158,32 @@ nsSVGInnerSVGFrame::GetType() const
 NS_IMETHODIMP
 nsSVGInnerSVGFrame::PaintSVG(nsSVGRenderState *aContext, nsRect *aDirtyRect)
 {
-  nsresult rv = NS_OK;
-
-  gfxContext *gfx = aContext->GetGfxContext();
-
-  gfx->Save();
+  gfxContextAutoSaveRestore autoSR;
 
   if (GetStyleDisplay()->IsScrollableOverflow()) {
+    float x, y, width, height;
+    static_cast<nsSVGSVGElement*>(mContent)->
+      GetAnimatedLengthValues(&x, &y, &width, &height, nsnull);
+
+    if (width <= 0 || height <= 0) {
+      return NS_OK;
+    }
+
     nsCOMPtr<nsIDOMSVGMatrix> clipTransform;
     if (!mPropagateTransform) {
       NS_NewSVGMatrix(getter_AddRefs(clipTransform));
     } else {
-      nsSVGContainerFrame *parent = static_cast<nsSVGContainerFrame*>
-                                               (mParent);
-      clipTransform = parent->GetCanvasTM();
+      clipTransform = static_cast<nsSVGContainerFrame*>(mParent)->GetCanvasTM();
     }
 
     if (clipTransform) {
-      nsSVGSVGElement *svg = static_cast<nsSVGSVGElement*>(mContent);
-
-      float x, y, width, height;
-      svg->GetAnimatedLengthValues(&x, &y, &width, &height, nsnull);
-
+      gfxContext *gfx = aContext->GetGfxContext();
+      autoSR.SetContext(gfx);
       nsSVGUtils::SetClipRect(gfx, clipTransform, x, y, width, height);
     }
   }
 
-  rv = nsSVGInnerSVGFrameBase::PaintSVG(aContext, aDirtyRect);
-
-  gfx->Restore();
-
-  return rv;
+  return nsSVGInnerSVGFrameBase::PaintSVG(aContext, aDirtyRect);
 }
 
 void