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Re: [css3-flexbox] flex-basis initial value should be 0px

From: fantasai <fantasai.lists@inkedblade.net>
Date: Tue, 29 May 2012 09:19:43 -0700
Message-ID: <4FC4F71F.3030501@inkedblade.net>
To: www-style@w3.org, "L. David Baron" <dbaron@dbaron.org>
On 05/24/2012 03:33 PM, Tab Atkins Jr. wrote:
> On Thu, May 24, 2012 at 3:29 PM, Tony Chang<tony@chromium.org>  wrote:
>>
>> That said, flex-basis: auto is about twice as slow as flex-basis: 0 (or any
>> other fixed value).  This is because before you can do the flex algorithm,
>> you need to compute the the basis (layout the child), then after you've run
>> the flex algorithm, you have to do a second layout at the computed width.
>>
>> I would prefer that the initial value of flex-basis be 0.  As Tab mentioned
>> up thread, this won't cause overflow anymore than flex-basis: auto.
>
> If dealing with the min-content restriction is indeed much cheaper
> than a full layout in WebKit (I already know that it's cheaper in FF),
> then yeah, I don't see any particular reason to default to 'auto' over
> '0'.  They're equally safe, and neither seems to be obviously more
> desirable as a default layout strategy.  Favoring the faster layout
> system here seems like a win.

A flex-basis of zero doesn't play very well with multi-line flexbox,
as it forces all the items to take their min-content width before
computing line breaks.

Also, I'm not sure that calculating max-content requires a full layout
any more than min-content does. Theoretically, it just requires keeping
a running total as you calculate the inline min-content lengths, and
resetting that total when you hit a forced break, right? (dbaron would
know for sure: if it's possible to optimize that way, I suspect Gecko
has done it.)

~fantasai
Received on Tuesday, 29 May 2012 16:20:23 GMT

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