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Re: [css3-transforms] Stack level of non-positioned transformed elements

From: Anton Prowse <prowse@moonhenge.net>
Date: Tue, 10 Jul 2012 23:15:41 +0200
Message-ID: <4FFC9B7D.6070008@moonhenge.net>
To: "www-style@w3.org" <www-style@w3.org>
CC: Øyvind Stenhaug <oyvinds@opera.com>
On 10/07/2012 19:06, Øyvind Stenhaug wrote:
> In CSS Transforms, various property values cause a stacking context to
> be established:
>
> - "In the HTML namespace, any value other than ‘none’ for the transform"
> (how about generic XML? Isn't this rather about anything other than SVG?)
> - "Any value other than ‘none’ for the transform" (this time no further
> qualification is given)
> - "A value of ‘preserve-3d’ for ‘transform-style’"
> - "The use of [the 'perspective'] property with any value other than
> ‘none’"
>
> However, nothing is said about the stack level of such a stacking
> context. I believe the spec needs to say that the stack level is 0 when
> the element is not positioned, similarly to what CSS Color says in the
> 'opacity' section.

May I suggest wording along the lines of:

   | If an element with <condition> is not positioned
   | then it is painted on the same layer, within its parent stacking
   | context, as positioned elements with stack level 0. If an element
   | with <condition> is positioned, the ‘z-index’ property
   | applies as described in [CSS21], except that if the used value
   | is 'auto' then the element behaves exactly as if it were '0'.

[In css3-color, a bit of a muddle occurs with the terminology.]

It's an open question whether we should simply force the used value to 
'0' in the case that the computed value is 'auto'.

Cheers,
Anton Prowse
http://dev.moonhenge.net
Received on Tuesday, 10 July 2012 21:16:13 GMT

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