Border-radius clipping on a stacking context causes descendants to not render

[Simon Fraser (smfr)]

Created attachment 244747 [details]
Testcase

Attached testcase shows a bug with border-radius clipping on a stacking context, with composited descendants.

[Simon Fraser (smfr)]

I have a fix for this.

[Simon Fraser (smfr)]

Created attachment 244842 [details]
Patch

[Byungseon(Sun) Shin]

I have verified that this change resolve the issue clearly on Mac Platform.
Thanks Simon.

[Byungseon(Sun) Shin]

I have found an issue on "Testcase that asserts on non-Mac" of https://bugs.webkit.org/show_bug.cgi?id=138551. 
It does not work on second test.

[Byungseon(Sun) Shin]

When container has border radius and clippingLayer with an offset value, it may need to apply border radius to container not to clippingLayer and then update offset value.
I have created a patch for it. 

One issue is when I change the offset value of clip Layer using inspector, it does not work well.

 // The clipping strategy depends on whether the rounded rect has equal corner radii.
 void GraphicsLayerCA::updateClippingStrategy(PlatformCALayer& clippingLayer, RefPtr<PlatformCALayer>& shapeMaskLayer, const FloatRoundedRect& roundedRect
)
 {
@@ -2085,7 +2072,15 @@ void GraphicsLayerCA::updateClippingStrategy(PlatformCALayer& clippingLayer, Ref
     clippingLayer.setCornerRadius(0);
     clippingLayer.setMask(shapeMaskLayer.get());
     
-    FloatRoundedRect offsetRoundedRect(clippingLayer.bounds(), roundedRect.radii());+
+    FloatRoundedRect offsetRoundedRect(roundedRect);
+
+    FloatRect clipRect = clippingLayer.bounds();
+    FloatPoint3D clipPos = clippingLayer.position();
+    FloatSize clipOffset = FloatSize(-(clipPos.x() - clipRect.width()/2), -(clipPos.y() - clipRect.height()/2));
+
+    offsetRoundedRect.move(clipOffset);
+
     shapeMaskLayer->setShapeRoundedRect(offsetRoundedRect);
 }

[Byungseon(Sun) Shin]

Created attachment 245090 [details]
test-result

[Byungseon(Sun) Shin]

Created attachment 245091 [details]
test-result-expected

[Byungseon(Sun) Shin]

Created attachment 245093 [details]
clip and border radius test

[Simon Fraser (smfr)]

Created attachment 245405 [details]
Patch

[WebKit Commit Bot]

Comment on attachment 245405 [details]
Patch

Clearing flags on attachment: 245405

Committed r179369: <http://trac.webkit.org/changeset/179369>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.