Re: [csswg-drafts] [css-gaps-1]: Change the initial value for insets property to be 0 (#13137)

Agenda+ to reconsider having or not having keyword(s).

From reading the minutes of the last F2F, it sounds like there was considerable interest in such a keyword. But as @oSamDavis points out, -50% can give an ugly result that is probably not what authors want. It's not something I feel great about attaching a keyword to.

The use case of joining segments across a grid with no spanners can be achieved with `rule-break: normal` (the default). The other common case we need to solve for is joining segments where they form a "T" or right angle. This is achievable with calc() if you do something like:

```css
--rule: 9px;
rule-width: 9px;
rule-interior-inset: calc(-50% - var(--rule) / 2);
```

Mockups of a few variants on the above: https://codepen.io/kevinbcmu/pen/NPRNKme

<img width="902" height="222" alt="Image" src="https://github.com/user-attachments/assets/a7f5a3cb-d8c7-4ca4-b456-929f540c8841" />

I could see perhaps assigning keywords to "-50% minus the width of the perpendicular decoration" and "-50% plus the width of the perpendicular decoration". But also, contrast with the border corners which give a beveled effect in this implementation (backgrounds-3 does not define a behavior here). I think it might be safer to leave the keyword space open for now and see what authors ask for once they start to use the feature more.

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Received on Thursday, 5 March 2026 00:17:07 UTC