Re: [csswg-drafts] [css-gaps-1] `overlap-join` with `between` rule visibility (#13697)

Got some good ideas from social media and have a proposal ready.

To recap, the spec currently defines shorthands to do the following:

1. Set all insets to the same value.
2. Set start insets separately from end insets, to achieve e.g. a "shortened vertical line" separator.
3. Set edge insets separately from interior insets, e.g. to extend decorations without exceeding the container bounds.

The proposed behavior change is to replace 3 with:

3. Set insets where there's no potential intersection separately from insets where there is a potential intersection.

This was @mochk's suggestion which seemed to have good support in the F2F discussion.

However, `edge`/`interior` don't accurately describe the distinction in the proposed new 3 because of the [donut case](https://github.com/w3c/csswg-drafts/issues/13697#issuecomment-4185489423). So we need new names. The top two suggestions from the social media discussion were `cap`/`join` and `open`/`closed`. Since we're already using `join` in the keyword that triggers the actual joining, I'll sub in `junction` for that one, and offer the following two slates of names for consideration:

```css
/* longhands */
[column|row]-rule-inset-start-cap
[column|row]-rule-inset-end-cap
[column|row]-rule-inset-start-junction
[column|row]-rule-inset-end-junction

/* start and end shorthands */
[column|row]-rule-inset-start
[column|row]-rule-inset-end

/* cap and junction shorthands */
[column|row]-rule-inset-cap
[column|row]-rule-inset-junction

/* universal shorthands */
[column|row]-rule-inset
```

-- OR --

```css
/* longhands */
[column|row]-rule-inset-open-start
[column|row]-rule-inset-open-end
[column|row]-rule-inset-closed-start
[column|row]-rule-inset-closed-end

/* start and end shorthands */
[column|row]-rule-inset-start
[column|row]-rule-inset-end

/* open and closed shorthands */
[column|row]-rule-inset-open
[column|row]-rule-inset-closed

/* universal shorthands */
[column|row]-rule-inset
```

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Received on Friday, 10 April 2026 22:24:55 UTC