[Webkit-unassigned] [Bug 55257] Support creating compositing layers for scrollable frames and iframes

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=55257





--- Comment #47 from Daniel Sievers <sievers at chromium.org>  2011-07-14 16:56:59 PST ---
(In reply to comment #46)
> > > Source/WebCore/rendering/RenderLayerCompositor.cpp:1289
> > > +    return (view->scrollWidth() != view->clientWidth())
> > > +        || (view->scrollHeight() != view->clientHeight());
> > 
> > What will cause compositing to be re-evaluated when the contents of the iframe grow such that it becomes scrollable?
> 
> I think this is a valid point. How are you handling this?

The evaluation is always performed after layout in FrameView.cpp, followed by a call to updateCompositingLayers().

When we were already compositing, and the iframe is not scrollable anymore, we will do a hierarchical/recursive update as is (which means we will leave it if there is no other reason left to be compositing).

When we were not compositing, and the iframe became scrollable, we will force compositing on this frame and enableCompositingMode() from updateCompositingLayers().

Also see attached test cases for enter-compositing and leave-compositing.

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