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Re: [css-grid] Resolve Intrinsic Track Sizes: min-content vs auto minimums

From: fantasai <fantasai.lists@inkedblade.net>
Date: Thu, 10 Dec 2015 17:18:00 -0500
To: Manuel Rego Casasnovas <rego@igalia.com>, www-style@w3.org
Message-ID: <5669FA18.5040700@inkedblade.net>
https://lists.w3.org/Archives/Public/www-style/2015Nov/0086.html
On 11/05/2015 08:26 AM, Manuel Rego Casasnovas wrote:
> Hi,
>
> I've a doubt regarding this section:
> https://drafts.csswg.org/css-grid/#algo-content
>
> Specifically in the point "1. Size tracks to fit non-spanning items" I'm
> wondering about the difference between "For min-content minimums" vs
> "For auto minimums". Summarizing the spec says:
> * For min-content minimums: [...] maximum of the items' min-content
> contributions.
> * For auto minimums: [...] specified by their respective min-width or
> min-height properties [...]
>
> So, let's use the following example [1]:
> <div style="display: grid; width: min-content;">
>    <div style="width: 100px; min-width: 0px;"></div>
> </div>
>
> If we've "grid-template-columns: auto;", we'll apply "for auto
> minimums", so we'd use 0px as specified by "min-width".
> The result would be a column of 0px width (and a grid of 0px too).
> The item will be 100px width anyway.
>
> However, if we've "grid-template-columns: min-content;", we'll apply the
> option "for min-content minimums", so we'd use the "min-content
> contribution" [2], which is 100px in this case.
> The result would be a column of 100px width (and a grid of 100px too).
>
> This difference between "auto" vs "min-content" column, in a grid being
> sized under a min-content constraint, seems really strange. Actually the
> fact that we can have an intrinsic column of 0px when the item inside
> that column has a 100px width is quite strange.
>
> The behavior described above is the current one implemented in both
> Blink and Firefox.
>
> Is this a wrong wording in the spec or a bug in the implementations?
> Should we update the spec?

This is a bug in the spec. :( We've fixed it as follows:
  # If the track has an ''auto'' <a>min track sizing function</a>,
  # set its <a>base size</a> to the maximum of its items’ “min-size
  # contributions”: the value specified by its respective 'min-width'
  # or 'min-height' properties (whichever matches the relevant axis)
  # if the specified size is ''auto'', or else the item’s <a>min-content
  # contribution</a>.

Let us know if this is clear, or if there remains any ambiguity
or error.

> On a related note, I've also doubts regarding "min-width: auto;".
> Imagine that we use "min-width: auto;" instead of "min-width: 0px;" in
> the previous example [3].
>
> I'm wondering what's what's the "min-content contribution" of the grid
> item in that case: 100px or 0px. I guess it's 100px, at least that's
> what both Blink and Firefox consider if we've "grid-template-columns:
> min-content;".
>
> However, if we've "grid-template-columns: auto;", Firefox considers it
> should use the "min-width" and follow the "implied minimum size" section.
> So according to the table there, it uses min(specified, content), which
> in this case would be min(100px, 0px), so Firefox is using 0px here.
> Blink is currently using 100px as size of this track.
>
> What's the expected behavior for this case?

Assuming we fixed it correctly above, this should be 100px.

Thank you very much for the detailed analysis, this was not a
straightforward error, and we really appreciate the time and
effort you put into reporting this!

~fantasai and TJ
Received on Thursday, 10 December 2015 22:18:37 UTC

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