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[css3-3d-transforms] z-index and transform-style:flat, z position follow-ups

From: Sylvain Galineau <sylvaing@microsoft.com>
Date: Fri, 29 Oct 2010 21:25:43 +0000
To: "www-style@w3.org" <www-style@w3.org>
Message-ID: <045A765940533D4CA4933A4A7E32597E2879B65D@TK5EX14MBXC111.redmond.corp.microsoft.com>
Following up on http://lists.w3.org/Archives/Public/www-style/2010Sep/0253.html.

1. transform-style flat and painting order

In the attached testcase, three overlapping sibling elements in a transform-style:flat 
container are translated to various Z positions. Their CSS painting order is A, B, C i.e. 
C above B above A.

In Safari, B is above A and C by virtue of its higher Z position. C is behind A due to 
its negative Z position. This remains true regardless of the z-index that's specified, 
if any.

In other words, the Z translation overrides the painting order. 

As Simon pointed out in his message:

# When transform-style is 'flatten', you can consider 3d transforms to be just a painting effect 
# (like 2d transforms), and to not affect the rendering order. (Note that WebKit does not currently 
# behave this way; it depth-sorts sibling elements with 3D transforms in this case).

Are we saying that in this case the rendering should be the same as one gets with a browser that
does not support 3D Transforms ?

2. Z position

# The Z position of an element is computed from the center of the border box.

Always, regardless of transform-origin ?
Received on Friday, 29 October 2010 21:26:23 UTC

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