[Webkit-unassigned] [Bug 111701] Basic child obscuration test for backgrounds

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=111701





--- Comment #20 from Antti Koivisto <koivisto at iki.fi>  2013-03-12 16:08:56 PST ---
(In reply to comment #19)
> I think this should be backgroundIsOpaqueInRect() since it only checks the background.

Ok, though caller doesn't really care and jumping through isOpaqueInRect() that just calls backgroundIsOpaqueInRect() seemed bit pointless.

> > Source/WebCore/rendering/RenderBox.cpp:1176
> > +    LayoutRect backgroundRect = borderBoxRect();
> 
> Why doesn't this needs to get the right background rect by checking style()->backgroundClip() like the function above?

The cases are not equivalent, opaqueInRect() needs smallest fully opaque rect for correctness while here we need maximum rect with any background pixels. borderBoxRect() is the maximum and the common case. No need to over-optimize this.

> I don't think the z-index check makes sense if we're not a stacking context, or we're not positioned. It would be better to deal with this if the child is a layer, and it should be explicit about us being a stacking context. It's very hard for me to think about whether this check is correct.

I'll move the test to the layer branch.

> Do we really have to wait 200ms? This will be a very slow test.

Probably not. 0 should work.

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