Re: [csswg-drafts] [css-multicol-2] column-height:0 (#12787)

The CSS Working Group just discussed `[css-multicol-2] column-height:0`, and agreed to the following:

* `RESOLVED: allow to be zero, let fragmentation spec ensure progress`

<details><summary>The full IRC log of that discussion</summary>
&lt;TabAtkins> rachelandrew: Noam asked if column-height:0 is allowed.<br>
&lt;TabAtkins> rachelandrew: not really a reason. Grid floors at 1px<br>
&lt;TabAtkins> rachelandrew: so probably what we want to do too<br>
&lt;florian> q+<br>
&lt;TabAtkins> florian: agree.<br>
&lt;astearns> ack kush<br>
&lt;astearns> ack florian<br>
&lt;TabAtkins> florian: so there's no restriction at syntax level, but floor at layout time<br>
&lt;dholbert> q+<br>
&lt;ntim> q+<br>
&lt;fantasai> TabAtkins: We do syntax restrictions all the time, could do 1px+ range which would still be closed range<br>
&lt;astearns> ack dholbert<br>
&lt;dbaron> There's a precedent for this with the perspective property and perspective() function.<br>
&lt;TabAtkins> dholbert: I weakly like having column-ehight:0 available for testing, useful for test printing<br>
&lt;TabAtkins> dholbert: can end up with printing with zero content area<br>
&lt;TabAtkins> dholbert: we make progress by putting *something* on the page<br>
&lt;fantasai> https://www.w3.org/TR/css-break-4/#breaking-rules<br>
&lt;fantasai> "To guarantee progress, fragmentainers are assumed to have a minimum block size of 1px regardless of their used size."<br>
&lt;TabAtkins> dholbert: so like *supporting* height:0<br>
&lt;astearns> ack ntim<br>
&lt;TabAtkins> ntim: if the restriction is at syntax level, what about calc()?<br>
&lt;fantasai> TabAtkins: Same as we handle 0px today<br>
&lt;emilio> q+<br>
&lt;fantasai> TabAtkins: clamp at used value tie<br>
&lt;astearns> ack fantasai<br>
&lt;TabAtkins> fantasai: we already have a rule that says fragmentatiners are assumed to have a min block size of 0px, regardless of used height<br>
&lt;TabAtkins> fantasai: we already have this case if the Multicol container itself has height:0px<br>
&lt;TabAtkins> fantasai: but each column will assume it's 1px high<br>
&lt;TabAtkins> fantasai: so we can do this clamp whenever. computed time, used time, or not at all and rely on the fragmentainer always laying out 1px of ontent<br>
&lt;dholbert> s/fragmentatiners are assumed to have a min block size of 0px/fragmentatiners are assumed to have a min block size of 1px/<br>
&lt;TabAtkins> astearns: I have concerns with relying on fragmentation module, there are layout concerns that aren't necessarily fragmentation concerns<br>
&lt;TabAtkins> astearns: i'd rather have things clamped before we start layout<br>
&lt;astearns> q?<br>
&lt;plinss> q+<br>
&lt;astearns> ack emilio<br>
&lt;TabAtkins> emilio: we'll have to clamp at used-value anyway, is there any benefit to restricting at syntax time?<br>
&lt;TabAtkins> emilio: if not i'd prefer to handle it at layout time<br>
&lt;TabAtkins> fantasai: I think key question is just whether the layout height is 1px, or just the fragmentation height?<br>
&lt;TabAtkins> florian: I think layout height.<br>
&lt;TabAtkins> s/min block size of 0px/min block size of 1px/<br>
&lt;TabAtkins> florian: even if there's overlap, you can at least see progress<br>
&lt;TabAtkins> plinss: want to agree with Elika/Emilio, handle it at layout time rather than syntax time<br>
&lt;fantasai> TabAtkins: We have lots of 0px restrictions, it's well-defined<br>
&lt;florian> q?<br>
&lt;TabAtkins> astearns: so clamping to 1px at used-value time?<br>
&lt;astearns> ack plinss<br>
&lt;TabAtkins> fantasai: yes<br>
&lt;dholbert> +1 to what plinss said<br>
&lt;TabAtkins> plinss: I think used-value time is even too early. let it be zero, require progress<br>
&lt;ntim> +1 to what plinss said<br>
&lt;ntim> +1 to what dholbert said about what plinss said<br>
&lt;TabAtkins> fantasai: proposed resolution: allow to be zero, let fragmentation spec ensure progress<br>
&lt;TabAtkins> astearns: I disagree but won't object<br>
&lt;TabAtkins> florian: same<br>
&lt;TabAtkins> plinss: I think that's the right concept<br>
&lt;TabAtkins> florian: can we poll? we agree it's not syntax time, want to see what our actual pref is<br>
&lt;TabAtkins> RESOLVED: allow to be zero, let fragmentation spec ensure progress<br>
</details>


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Received on Friday, 14 November 2025 03:19:10 UTC