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Re: [CSS3-color] Errata

From: Anton Prowse <prowse@moonhenge.net>
Date: Tue, 17 Jul 2012 20:18:41 +0200
Message-ID: <5005AC81.3040401@moonhenge.net>
To: www-style@w3.org
CC: Chris Lilley <chris@w3.org>
On 17/07/2012 15:35, Chris Lilley wrote:
> On Sunday, April 29, 2012, 9:34:50 PM, Anton wrote:
>
> AP> Really sorry - I thought I'd sent a reply to this whilst at the Paris F2F
> AP> but I don't think I actually did :-(.
>
>>> Comment 3
>
>>> Your proposed wording isn't quite sufficient because "treated as
>>> though it has the index: 0" also has an effect on the painting level
>>> of descendents.
>
>>> Instead, we suggest to address your comment by changing
>
>>> "except that ?auto? is treated as ?0?"
>
>>> to
>
>>> "except that a computed value of 'auto' behaves as if its z-index
>>> were zero"
>
>>> to make it clear that it doesn't change the computed value.
>
> AP> I don't think that makes much grammatical sense, but I'm happy with the
> AP> approach; it's follows the same lines as the updated suggestion that I
> AP> made in [1] in response to comments.
>
> AP> The heart of the issue is that it's not entirely clear what "behaves"
> AP> means!  Is it obvious that you intend that the element takes
> AP> responsibility for painting its positioned descendents (ie that
> AP> responsibility doesn't bubble up to the nearest ancestor positioned
> AP> element with integer z-index), but I wish it were more explicit that
> AP> the used value doesn't become '0'.
>
> AP> Here's another possibility:
>
> AP>   | If an element with opacity less than 1 is not positioned
> AP>   | then it is painted on the same layer, within its parent stacking
> AP>   | context, as positioned elements with stack level 0. If an element
> AP>   | with opacity less than 1 is positioned, the ?z-index? property
> AP>   | applies as described in [CSS21], except that if the used value
> AP>   | is 'auto' then the element behaves exactly as if it were '0'.
>
> AP> [Note that I prefer my first sentence over the one that's in the spec,
> AP> where a bit of a muddle occurs with "paint the layer" and "at the same
> AP> stacking order".  My sentence precisely matches what's now CSS21
> AP> terminology.]
>
> Yes, its better to match the CSS 2.1 teminology.
>
> AP> This addresses my concern about used value, and it's implicit that a
> AP> computed value of 'auto' may still result, since that's the only way of
> AP> ending up with a used value of 'auto'.
>
> AP> In fact, would it not be much simpler to force the used value to '0' in
> AP> the case that the computed value is 'auto'?  There wouldn't need to be
> AP> any hand-waving at all then!
>
> That seems like a bigger change, and not necessarily compatible with existing implementations. So I would like to propose that we accept your proposed 'another possibility' wording.
>
> Please confirm that it is acceptable, so I can update the errata.

Thanks Chris, this is fine of course.

Cheers,
Anton Prowse
http://dev.moonhenge.net
Received on Tuesday, 17 July 2012 18:19:12 GMT

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