[Webkit-unassigned] [Bug 142783] RenderLayerCompositor: only create backing for visible and non-empty layers

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=142783

--- Comment #8 from Anton Obzhirov <a.obzhirov at samsung.com> ---
(In reply to comment #6)
> (In reply to comment #4)
> > Created attachment 248943 [details]
> > Example of positionned divs
> > 
> > In the attached exmaple, all the divs become composited (creates a backing),
> > because of the video tag.
> 
> Not on Mac. I get one big layer for the rootmost view and none inside of it.
> 
> > If the video tag is added after all the divs or in a zindex different than 0
> > then all the divs do not become composited.
> 
> Odd that there's an ordering difference.
> 
> > So is it really an expected behaviour  for neasted divs to all become
> > composited this way ?
> 
> No. Are you testing webkit TOT?
> 
> > About stacking context the following doc is very helpful:
> > 
> > "When no z-index property is specified, elements are rendered on the default
> > rendering layer 0 (zero)." , but if I put 0 manually the divs do not become
> > composited (if I put auto they become composited)
> > 
> > "A stacking context is formed, anywhere in the document, by any element
> > which is positioned (absolutely or relatively) with a z-index value other
> > than "auto" "
> > It seems to behave the opposite as said juste before.
> 
> z-index:0 create stacking context, but has z-index 0 in its parent stacking
> context. z-index: auto does not create stacking context.

Actually, in the example Julien attached all divs have -index: 0;.
So if you used the same unmodified example you got wrong behaviour on Mac.

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