[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


Simon Fraser (smfr) <simon.fraser at apple.com> changed:

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--- Comment #36 from Simon Fraser (smfr) <simon.fraser at apple.com>  2011-03-18 12:54:11 PST ---
(From update of attachment 85016)
View in context: https://bugs.webkit.org/attachment.cgi?id=85016&action=review

> Source/WebCore/rendering/RenderLayerCompositor.cpp:1259
> +bool RenderLayerCompositor::requiresCompositingForScrollableFrame(RenderObject* renderer) const
> +{
> +    if (!(m_compositingTriggers & ChromeClient::ScrollableFrameTrigger))
> +        return false;
> +
> +    if (!renderer->isRenderView())

Given the phrasing works, I'd expect this to be called on the renderer in the parent document (the RenderIFrame or whatever), and affect compositing in the parent document. However, that's not what you're doing.

So I think it's wrong to add a requiresCompositingForScrollableFrame(), and wasteful to call requiresCompositingForScrollableFrame() for every renderer in the document when it would only ever apply to the root.

I think you should just do the root compositing check in one place.

> 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?

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