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[css-transforms] Should transform-style: preserve-3d create containing block for positioned descendants?

From: Simon Fraser <smfr@me.com>
Date: Thu, 11 Dec 2014 10:47:54 -0800
Message-id: <66B2D1D5-85EF-4F77-AC6D-BCF86752EC6B@me.com>
To: www-style list <www-style@w3.org>
There is disagreement among implementations about whether "transform-style: preserve-3d” creates containing block for positions descendants.

The working draft[1] says in the prose:

> A 3D rendering context is established by a a transformable element whose computed value for transform-style is preserve-3d, and which itself is not part of a 3D rendering context. Note that such an element is always a containing block.


but we don't explicitly call this out under the transform-style property. The new spec text doesn't require that preserve-3d create containing block, and logically I see no reason why it should. (I’m also not sure why perspective has to create a containing block.)

WebKit/Blink have this behavior because of a bug[2]. Firefox has this behavior too, possibly because they copied WebKit behavior, or went by the spec prose. IE 11 does not have this behavior.

Testcase:
http://jsbin.com/budadutude/1/edit <http://jsbin.com/budadutude/1/edit>

Bug:
https://www.w3.org/Bugs/Public/show_bug.cgi?id=27566

Thoughts?
Simon

[1] http://www.w3.org/TR/2013/WD-css-transforms-1-20131126/ <http://www.w3.org/TR/2013/WD-css-transforms-1-20131126/>
[2] https://bugs.webkit.org/show_bug.cgi?id=138122
Received on Thursday, 11 December 2014 18:48:30 UTC

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