[Webkit-unassigned] [Bug 93174] RenderLayerBacking must call GraphicsLayer::setContentsToImage when the image is changed.

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=93174


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

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 Attachment #156509|review?, commit-queue?      |review-, commit-queue-
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--- Comment #3 from Simon Fraser (smfr) <simon.fraser at apple.com>  2012-08-03 22:35:59 PST ---
(From update of attachment 156509)
View in context: https://bugs.webkit.org/attachment.cgi?id=156509&action=review

> Source/WebCore/ChangeLog:13
> +        Currently, layout indirectly call RenderLayerBacking::updateGraphicsLayerConfiguration()
> +        and updateGraphicsLayerConfiguration() indirectly call GraphicsLayer::setContentsToImage().
> +        It burdens all accelerated compositing implementations because each implementation
> +        should check if the image is changed.

This comment is confusing. updateGraphicsLayerConfiguration() isn't the place where animated GIFs get updated on compositing layers; that happens via RenderBoxModelObject::contentChanged() which ends up in RenderLayerBacking::contentChanged().

> Source/WebCore/rendering/RenderLayerBacking.cpp:1089
> +    NativeImagePtr newNativeImagePtr = image->nativeImageForCurrentFrame();
> +    if (newNativeImagePtr != m_compositedNativeImagePtr) {
> +        m_compositedNativeImagePtr = newNativeImagePtr;
> +
> +        // This is a no-op if the layer doesn't have an inner layer for the image.
> +        m_graphicsLayer->setContentsToImage(image);

It seems odd to inspect the NativeImagePtr here, but still send the Image down to GraphicsLayer.

This code also makes the assumption that pointer equality on a NativeImagePtr is a valid way to tell if the image is unchanged. That may not hold for all platforms. I think the platform code should continue to make the decision about whether the image has changed.

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