Assertion when turning Accelerated Compositing off on a composited page

[Simon Fraser (smfr)]

When turning off Accelerated Compositing, we hit one of the

    ASSERT(willBeComposited == needsToBeComposited(layer));

assertions in RenderLayerCompositor::computeCompositingRequirements().

[Simon Fraser (smfr)]

Created attachment 61724 [details]
Patch

[Darin Adler]

Comment on attachment 61724 [details]
Patch

Does this fix only the assertion, or does it affect behavior too? If it does have an effect on behavior, what is that effect?

[Simon Fraser (smfr)]

There is no change in behavior; we used to do a bit of extra work for the one call to computeCompositingRequirements() after compositing was disabled, because we thought we needed to make layers, and then when we tried to, noticed that m_hasAcceleratedCompositing was false.

With the patch we never even try to make layers in that situation.

[Simon Fraser (smfr)]

http://trac.webkit.org/changeset/63573

[qi]

*** Bug 42582 has been marked as a duplicate of this bug. ***

[Balazs Kelemen]

I have a similar issue: https://bugs.webkit.org/show_bug.cgi?id=74511. When running fast/multicol/pagination-v-vertical-lr.html it hits the assertion in RenderLayerCompositor:

// If we just entered compositing mode, the root will have become composited (as long as accelerated compositing is enabled).
if (layer->isRootLayer()) {
    if (inCompositingMode() && m_hasAcceleratedCompositing)
        willBeComposited = true;
}
    
ASSERT(willBeComposited == needsToBeComposited(layer)); <<<<<<<<<<

In this case the layer is a root layer, and both inCompositingMode() and m_hasAcceleratedCompositing are true, but needsToBeComposited(layer) is false because layer->isNormalFlowOnly() => !layer->isSelfPaintingLayer() => !canBeComposited(layer)
Do you think another condition could be sufficient? i.e:
-if (layer->isRootLayer()) {
+if (layer->isRootLayer() && canBeComposited(layer))

Thanks in advance to your help!

[Simon Fraser (smfr)]

(In reply to comment #6)
> I have a similar issue: https://bugs.webkit.org/show_bug.cgi?id=74511. When running fast/multicol/pagination-v-vertical-lr.html it hits the assertion in RenderLayerCompositor:

Please file a new bug for this assertion.

> In this case the layer is a root layer, and both inCompositingMode() and m_hasAcceleratedCompositing are true, but needsToBeComposited(layer) is false because layer->isNormalFlowOnly() => !layer->isSelfPaintingLayer() => !canBeComposited(layer)
> Do you think another condition could be sufficient? i.e:
> -if (layer->isRootLayer()) {
> +if (layer->isRootLayer() && canBeComposited(layer))

If the root layer cannot be composited, then all kinds of stuff will break. I think we'll have to fix this another way.

[Balazs Kelemen]

(In reply to comment #7)
> (In reply to comment #6)
> > I have a similar issue: https://bugs.webkit.org/show_bug.cgi?id=74511. When running fast/multicol/pagination-v-vertical-lr.html it hits the assertion in RenderLayerCompositor:
> 
> Please file a new bug for this assertion.

Filed https://bugs.webkit.org/show_bug.cgi?id=74999.