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[csswg-drafts] [css-color-4] Paint order of non-positioned stacking context (#3793)

From: Simon Sapin via GitHub <sysbot+gh@w3.org>
Date: Tue, 02 Apr 2019 21:12:34 +0000
To: public-css-archive@w3.org
Message-ID: <issues.opened-428446853-1554239553-sysbot+gh@w3.org>
SimonSapin has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-color-4] Paint order of non-positioned stacking context ==
CSS Color Level 3 defines:

https://drafts.csswg.org/css-color-3/#transparency
>  If an element with `opacity` less than 1 is not positioned, then it is painted on the same layer, within its parent stacking context, as positioned elements with stack level 0.

However this sentence was apparently removed from Level 4: https://drafts.csswg.org/css-color/#transparency

I think this removal is a bug and that definition is necessary, because CSS 2 appendix E is written with the assumption that elements that create a stacking context are all positioned. (This is because only the `z-index` property creates a stacking context in CSS 2, and it only applies to positioned elements.)

css-transforms has an alternative wording that also works:

https://drafts.csswg.org/css-transforms-1/#transform-rendering
> For elements whose layout is governed by the CSS box model, any value other than `none` for the `transform` property results in the creation of a stacking context. Implementations must paint the layer it creates, within its parent stacking context, at the same stacking order that would be used if it were a positioned element with `z-index: 0`. 

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/3793 using your GitHub account
Received on Tuesday, 2 April 2019 21:12:37 UTC

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