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Re: [css3-flexbox] min-width/height: auto, its Computed Value line, and "computes to" prose

From: fantasai <fantasai.lists@inkedblade.net>
Date: Sun, 20 May 2012 22:33:34 -0700
Message-ID: <4FB9D3AE.3090801@inkedblade.net>
To: www-style@w3.org
On 05/19/2012 03:44 PM, Tab Atkins Jr. wrote:
> On Sat, May 19, 2012 at 11:45 AM, L. David Baron<dbaron@dbaron.org>  wrote:
>> http://dev.w3.org/csswg/css3-flexbox/#min-size-auto says:
>>   #  New Computed Value:   the percentage as specified or the
>>   #                        absolute length or a keyword
>> where the "or a keyword" is an addition relative to
>> http://www.w3.org/TR/CSS21/visudet.html#min-max-widths .
>>
>> I think the "New Computed Value" line is correct, the 'auto' keyword
>> should always be the computed value, and the second quoted piece of
>> prose should be changed to avoid the term "computes".

The concern here was backwards-compatibility, and there are two
options for how this could behave:
   - auto always computes to auto
   - auto computes to 0 where needed for back-compat,
     currently blocks and tables

There wasn't very much discussion on which option we should take,
other than you suggesting to have it compute to 0 for now on
tables and maybe decide later whether it could compute to ''auto'',
or to ''min-content''. We took the option that was resolved in the
minutes, which computes it to ''0''. But if it's not needed for
back-compat, then it could certainly compute to ''auto''.

>> This would avoid implementation complexity and the need to update
>> http://wiki.csswg.org/spec/property-dependencies to reflect this
>> additional dependency.

I think we need to have a discussion on what the intention of
computed values are, because originally they were the used
value, and then, because that was hard to implement, they were
degraded to "the value as far as you can compute without doing
layout", and now you're arguing they should just be the specified
value with variant syntaxes equated.

> What effect would this have on Block Layout margin-collapsing, which
> assigns special meaning to a min-height other than 0?

If that's the concern, we can always clarify that ''auto'' is
equivalent to ''0''  on blocks, even in the case of margin
collapsing. It's not a blocker on what we decide to do here.

~fantasai
Received on Monday, 21 May 2012 05:34:07 GMT

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