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Re: [CSS21] zindex.html E.2 issue: ordering contradictions

From: Peter Moulder <peter.moulder@monash.edu>
Date: Mon, 07 Mar 2011 03:29:31 +1100
To: www-style@w3.org
Message-id: <20110306162931.GB16349@bowman.infotech.monash.edu.au>
Note that this issue is mostly editorial (even if requiring more
thought to fix than most editorial issues), i.e. I think there's
agreement on the essentials of the correct behaviour (which I suspect
corresponds to the behaviour that Anton Prowse describes), and it's
mostly just a matter of making sure that appendix E actually
corresponds to that behaviour.

On Sun, Nov 07, 2010 at 10:22:58AM +0100, Anton Prowse wrote:
> On 05/11/2010 04:28, Peter Moulder wrote:
> >If I understand correctly, zindex.html as currently written includes some
> >items (say the background image of element X) more than once: various
> >places in the list include "all [qualifier] descendents [of E]", which
> >typically includes descendents of some different E that's also included in
> >the painting order.
> I believe that the issues you're raising in your post are a subset
> of those I raised at the start of my campaign to get 9.9.1
> changed.[1]

It may well be that Anton's suggested changes (if applied to appendix E
and not just §9.9) would fix the problem.  E.g. introducing a term like
Anton's pseudo–stacking context may well be useful as part of the fix.

If there's concern that this report may merely duplicate issues Anton
has raised, then I'm happy to wait until those issues are addressed and
modify (or retract) this issue report once a revised version of
appendix E is available.

(Note of course that this only applies if appendix E is in fact
changed as part of that: obviously no change to §9.9 alone could be
enough to remove any contradictions within appendix E.)

> In particular, 9.9.1 states: [...]

Similarly, the content of chapter 9 is irrelevant to whether there are
contradictions within appendix E.  It may be that chapter 9 gives a
clue as to what the correct wording in appendix E should be, but
appendix E would still need to be changed.

> What we're really doing when compositing the document is determining
> the dependants of each stacking context and pseudo–stacking context
> (terms which I defined in my original proposals (see [1])), and
> then, working upwards from the innermost (pseudo–)stacking context,
> compositing said context according to the rules of E2 and treating
> any already-composited context as atomic.
> [...]
> Not so, because ...

That may well be what we want the text to say, and may be what the text
would say under Anton's proposed edits; however, it's not what the Dec7
working draft says, which does have the problem.

> There is no "double treatment" of any box.

I believe I showed in my previous post that appendix E in the Dec7
working draft does indeed give double treatment to some boxes, that
section E2 does in fact include some boxes in more than one float

Received on Sunday, 6 March 2011 16:30:01 UTC

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