Re: [csswg-drafts] [css-gaps] Gap decorations with collapsed gutters (#11814)

I tracked the text specifying that gutters overlap back to https://github.com/w3c/csswg-drafts/commit/ac370302681c2425777a57b8461281e1bd88afc8 by @tabatkins, which was introduced after discussion in #172, in which @fantasai [wrote](https://github.com/w3c/csswg-drafts/issues/172#issuecomment-227570769):
> We ended up collapsing gutters by specifying that they coincide, because the location of the gutters and the lines can be detected by abspos, so we can't just drop them. If at some point we add explicitly collapsing columns as a feature (e.g. via `visibility: collapse`), this behavior would be the correct one to have for that as well.

Meanwhile, Gaps leaves the definition of where gutters exist to other specifications. That's intentional, so that gap decorations can be defined the same way regardless of container type. So from the perspective of Gaps, if the gaps overlap, then the decorations would overlap as well.

With those points in mind, I was tempted to look for a solution in Grid, where we'd somehow still collapse grid line positions but consolidate down to a single gap. But that got me worried about introducing weird discontinuities in cases where gaps cross the threshold from being exactly-overlapping to almost-overlapping (animation perhaps?).

I guess my take depends on whether such discontinuities could be a thing. If they could, then overlapping decorations seems like not-great-but-least-surprising behavior. If that's not a situation we need to worry about, then my preference would be to solve this with some sort of change to Grid that makes sense both for gap decorations and for abspos per #10813.

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Received on Monday, 24 March 2025 18:27:43 UTC