Re: [csswg-drafts] [css-gaps-1] Gap intersection point definition might need updating for multi-col (#12084)

I dug into this a bit more. Excerpts from https://www.w3.org/TR/css-multicol-1/#the-multi-column-model:

> Within each [multicol line](https://www.w3.org/TR/css-multicol-1/#multi-column-line) in the multi-column container, adjacent column boxes are separated by a column gap, which may contain a column rule. All column gaps in the same multi-column container are equal. All column rules in the same multi-column container are also equal, if they appear; column rules only appear between columns that both have content.
>
> In the simplest case a multicol container will contain only one line of columns, and the height of each column will be equivalent to the used height of the multi-column container’s content box. However, [fragmentation](https://www.w3.org/TR/css-break-4/#fragmentation) or [spanners](https://www.w3.org/TR/css-multicol-1/#multi-column-spanner) can split the content of the [multi-column container](https://www.w3.org/TR/css-multicol-1/#multi-column-container) into multiple [multicol lines](https://www.w3.org/TR/css-multicol-1/#multi-column-line).

Key points:
1. Gaps are defined to exist between column boxes *per multicol line*.
2. A spanner triggers creation of a *new* multicol line.

This reminds me of where we ended up with flexbox in https://github.com/w3c/csswg-drafts/issues/11911 where each flex line has its own set of gaps, even if they happen to line up with each other. I closed that issue after adding an example and a note, but looking at it again I think the normative definition still doesn't cover multi-line flex as intended.

So maybe the first bullet for the gap intersection point definition needs to be rewritten so that, instead of talking about an intersection with the edge of the container, it talks about the start or end of a "gap" as defined by the container type? With perhaps a couple more clarifying examples and/or notes illustrating how these get applied.

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Received on Thursday, 3 July 2025 20:52:54 UTC