[Webkit-unassigned] [Bug 182673] [GTK] whatsapp web blurry in some parts, sharp on others

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=182673

--- Comment #3 from Miguel Gomez <magomez at igalia.com> ---
(In reply to Carlos Garcia Campos from comment #2)
> Does it also happen with AC disabled?

Nope.

It's a problem with the size of the backingStore created by CoordinatedGraphicsLayer, which is not following the required scale factors.

CoordinatedGraphicsLayer::createBackingStore() uses effectiveContentsScale() to get the scale factor to apply. But effectiveContentsScale() returns always 1 if selfOrAncestorHaveNonAffineTransforms() returns true.

The weird part is that selfOrAncestorHaveNonAffineTransforms() returns true if the layer has an ongoing animation, which effectively means that animated layers won't use the appropriate backingStore size.

I don't see why that is intended. I've looked into that code history and there is a comment about "disabling progressive tiling for animated layers" years ago but I don't see the reason to do it. Maybe at hat point they wanted to perform the scaling during the composition stage to save memory. But the problem with that is that it causes blurry rendering, as we can see in this bug.

IMO we should be using the scale factor even if the layer is animated.

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