Bug 1052913 - Clean up some nsSVGClipPathFrame code and add some documentation to make it clearer. r=dholbert

layout/svg/nsSVGClipPathFrame.cpp

@@ -28,9 +28,9 @@ NS_NewSVGClipPathFrame(nsIPresShell* aPresShell, nsStyleContext* aContext)
 NS_IMPL_FRAMEARENA_HELPERS(nsSVGClipPathFrame)
 
 nsresult
-nsSVGClipPathFrame::ClipPaint(nsRenderingContext* aContext,
-                              nsIFrame* aParent,
-                              const gfxMatrix &aMatrix)
+nsSVGClipPathFrame::ApplyClipOrPaintClipMask(nsRenderingContext* aContext,
+                                             nsIFrame* aClippedFrame,
+                                             const gfxMatrix& aMatrix)
 {
   // If the flag is set when we get here, it means this clipPath frame
   // has already been used painting the current clip, and the document
@@ -41,7 +41,7 @@ nsSVGClipPathFrame::ClipPaint(nsRenderingContext* aContext,
   }
   AutoClipPathReferencer clipRef(this);
 
-  mMatrixForChildren = GetClipPathTransform(aParent) * aMatrix;
+  mMatrixForChildren = GetClipPathTransform(aClippedFrame) * aMatrix;
 
   gfxContext *gfx = aContext->ThebesContext();
 
@@ -78,7 +78,7 @@ nsSVGClipPathFrame::ClipPaint(nsRenderingContext* aContext,
     referencedClipIsTrivial = clipPathFrame->IsTrivial();
     gfx->Save();
     if (referencedClipIsTrivial) {
-      clipPathFrame->ClipPaint(aContext, aParent, aMatrix);
+      clipPathFrame->ApplyClipOrPaintClipMask(aContext, aClippedFrame, aMatrix);
     } else {
       gfx->PushGroup(gfxContentType::ALPHA);
     }
@@ -104,7 +104,7 @@ nsSVGClipPathFrame::ClipPaint(nsRenderingContext* aContext,
         isTrivial = clipPathFrame->IsTrivial();
         gfx->Save();
         if (isTrivial) {
-          clipPathFrame->ClipPaint(aContext, aParent, aMatrix);
+          clipPathFrame->ApplyClipOrPaintClipMask(aContext, aClippedFrame, aMatrix);
         } else {
           gfx->PushGroup(gfxContentType::ALPHA);
         }
@@ -119,7 +119,7 @@ nsSVGClipPathFrame::ClipPaint(nsRenderingContext* aContext,
           nsRefPtr<gfxPattern> clipMaskSurface;
           gfx->PushGroup(gfxContentType::ALPHA);
 
-          clipPathFrame->ClipPaint(aContext, aParent, aMatrix);
+          clipPathFrame->ApplyClipOrPaintClipMask(aContext, aClippedFrame, aMatrix);
           clipMaskSurface = gfx->PopGroup();
 
           if (clipMaskSurface) {
@@ -138,7 +138,7 @@ nsSVGClipPathFrame::ClipPaint(nsRenderingContext* aContext,
       nsRefPtr<gfxPattern> clipMaskSurface;
       gfx->PushGroup(gfxContentType::ALPHA);
 
-      clipPathFrame->ClipPaint(aContext, aParent, aMatrix);
+      clipPathFrame->ApplyClipOrPaintClipMask(aContext, aClippedFrame, aMatrix);
       clipMaskSurface = gfx->PopGroup();
 
       if (clipMaskSurface) {

layout/svg/nsSVGClipPathFrame.h

@@ -37,9 +37,21 @@ public:
                                 const nsDisplayListSet& aLists) MOZ_OVERRIDE {}
 
   // nsSVGClipPathFrame methods:
-  nsresult ClipPaint(nsRenderingContext* aContext,
-                     nsIFrame* aParent,
-                     const gfxMatrix &aMatrix);
+
+  /**
+   * If the SVG clipPath is simple (as determined by the IsTrivial() method),
+   * calling this method simply pushes a clip path onto the DrawTarget.  If the
+   * SVG clipPath is not simple then calling this method will paint the
+   * clipPath's contents (geometry being filled only, with opaque black) to the
+   * DrawTarget.  In this latter case callers are expected to first push a
+   * group before calling this method, then pop the group after calling and use
+   * it as a mask to mask the clipped frame.
+   *
+   * XXXjwatt Maybe split this into two methods.
+   */
+  nsresult ApplyClipOrPaintClipMask(nsRenderingContext* aContext,
+                                    nsIFrame* aClippedFrame,
+                                    const gfxMatrix &aMatrix);
 
   /**
    * aPoint is expected to be in aClippedFrame's SVG user space.

layout/svg/nsSVGIntegrationUtils.cpp

@@ -515,7 +515,7 @@ nsSVGIntegrationUtils::PaintFramesWithEffects(nsRenderingContext* aCtx,
    */
   if (clipPathFrame && isTrivialClip) {
     gfx->Save();
-    clipPathFrame->ClipPaint(aCtx, aFrame, cssPxToDevPxMatrix);
+    clipPathFrame->ApplyClipOrPaintClipMask(aCtx, aFrame, cssPxToDevPxMatrix);
   }
 
   /* Paint the child */
@@ -552,7 +552,7 @@ nsSVGIntegrationUtils::PaintFramesWithEffects(nsRenderingContext* aCtx,
   if (clipPathFrame && !isTrivialClip) {
     gfx->PushGroup(gfxContentType::COLOR_ALPHA);
 
-    nsresult rv = clipPathFrame->ClipPaint(aCtx, aFrame, cssPxToDevPxMatrix);
+    nsresult rv = clipPathFrame->ApplyClipOrPaintClipMask(aCtx, aFrame, cssPxToDevPxMatrix);
     clipMaskSurface = gfx->PopGroup();
 
     if (NS_SUCCEEDED(rv) && clipMaskSurface) {

layout/svg/nsSVGUtils.cpp

@@ -609,7 +609,7 @@ nsSVGUtils::PaintFrameWithEffects(nsRenderingContext *aContext,
    */
   if (clipPathFrame && isTrivialClip) {
     gfx->Save();
-    clipPathFrame->ClipPaint(aContext, aFrame, matrix);
+    clipPathFrame->ApplyClipOrPaintClipMask(aContext, aFrame, matrix);
   }
 
   /* Paint the child */
@@ -661,7 +661,7 @@ nsSVGUtils::PaintFrameWithEffects(nsRenderingContext *aContext,
   if (clipPathFrame && !isTrivialClip) {
     gfx->PushGroup(gfxContentType::COLOR_ALPHA);
 
-    nsresult rv = clipPathFrame->ClipPaint(aContext, aFrame, matrix);
+    nsresult rv = clipPathFrame->ApplyClipOrPaintClipMask(aContext, aFrame, matrix);
     clipMaskSurface = gfx->PopGroup();
 
     if (NS_SUCCEEDED(rv) && clipMaskSurface) {