W3C home > Mailing lists > Public > www-style@w3.org > May 2013

Re: margin-inline-start and friends

From: L. David Baron <dbaron@dbaron.org>
Date: Thu, 9 May 2013 16:09:56 -0700
To: "Tab Atkins Jr." <jackalmage@gmail.com>
Cc: Simon Sapin <simon.sapin@exyr.org>, fantasai <fantasai.lists@inkedblade.net>, www-style list <www-style@w3.org>
Message-ID: <20130509230956.GA21230@crum.dbaron.org>
On Thursday 2013-05-09 15:10 -0700, Tab Atkins Jr. wrote:
> On Thu, May 9, 2013 at 3:03 PM, L. David Baron <dbaron@dbaron.org> wrote:
> > On Thursday 2013-05-09 14:59 -0700, Tab Atkins Jr. wrote:
> >> On Thu, May 9, 2013 at 2:56 PM, Simon Sapin <simon.sapin@exyr.org> wrote:
> >> > Le 09/05/2013 23:51, fantasai a Γ©crit :
> >> >> You need to cascade and compute writing-mode and direction first,
> >> >> then cascade the logical properties. Antenna House Formatter has
> >> >> an implementation of this, and helped us to specify it.
> >> >
> >> > Ah, I see. Interesting. Did implementers notice some runtime cost in doing
> >> > the cascade in two passes?
> >>
> >> That's not necessary, under David's proposal.  You can cascade them
> >> together and then determine at computed-value time what property
> >> affect which sides.
> >
> > No, it does require doing the cascade separately.  But Gecko already
> > does cascading separately for groups of properties, so it's fine for
> > us.
> 
> Hm, can you explain why?  As far as I can tell, it should work fine to
> cascade them together, so long as you're okay with the "real" values
> only showing up at computed-value time.

I should probably say this more clearly:

 * for LTR, margin-start and margin-left must be cascaded together

 * this requires that the direction be known before cascading margin
   properties

 * this means the cascade has two passes (which is what Simon was
   asking about), with direction being done in the first pass and
   margins (cascaded together) in the second pass

-David

-- 
π„ž   L. David Baron                         http://dbaron.org/   𝄂
𝄒   Mozilla                           http://www.mozilla.org/   𝄂
Received on Thursday, 9 May 2013 23:10:25 UTC

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