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RE: [css-sizing][css-flexbox] intrinsic min/max-width/height values and percentage children

From: Greg Whitworth <gwhit@microsoft.com>
Date: Fri, 31 Jul 2015 02:33:54 +0000
To: Greg Whitworth <gwhit@microsoft.com>, Daniel Holbert <dholbert@mozilla.com>, Tab Atkins Jr. <jackalmage@gmail.com>
CC: www-style list <www-style@w3.org>
Message-ID: <CY1PR03MB14391158130B8D5BAA1677BBA48A0@CY1PR03MB1439.namprd03.prod.outlook.com>
> > > If you have min-width:auto, then you need to calculate the
> > > min-content size of the flex item.  This doesn't care about the
> > > width or flex-basis, it cares about the min-size contributions of
> > > the flex item's children.  We thus can't treat a percentage on a
> > > child as resolving against a definite width here, because we're in
> > > the process of computing that width; but if the width isn't
> > > definite, then the percentage becomes auto *here*, and then a
> > > resolved definite value *later*, which is confusing and weird and
> > > two-pass, and we'd like to avoid two-pass layout in the default
> > > case.  (In other words, this becomes just a variant of the option C
> > > two-pass layout.)
> >
> > Right -- this what I was trying to get across in
> >   https://lists.w3.org/Archives/Public/www-style/2015Feb/0489.html

> > and elsewhere in that thread, but you explained it here better than I did.
> >
> > > So I think we're screwed and need to go with option A.
> >
> > This is unfortunate, but I think I agree, for perf reasons (to avoid
> > getting
> > O(n^2) behavior *by default* for some pretty simple cases, due to the
> > two- pass layout that can't really be avoided).
> >
> > ~Daniel
> 
> Just so that I'm not talking about something entirely different, I created a
> simple test case: http://jsbin.com/nomopewego/1/edit
> If I'm correct than you're suggesting that the red box should be able to

I meant _shouldn't_ here, sorry about that

> resolve 50% since it doesn't know (when we're calculating the width, what to
> resolve against).
> 
> If that is indeed what you're saying, I don't think resolving the percentages is
> confusing, I think not supporting them in this instance will be confusing. The
> fact that you need to do a two pass layout to resolve them doesn't seem to
> be hindrance at this point, are you receiving bug reports regarding poor perf
> on flex dependent sites?
> 
> Thanks,
> Greg
Received on Friday, 31 July 2015 02:34:30 UTC

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