[csswg-drafts] [css-overflow-5] Making ::scroll-marker existence unconditional? (#11600)

tabatkins has just created a new issue for https://github.com/w3c/csswg-drafts:

== [css-overflow-5] Making ::scroll-marker existence unconditional? ==
Currently, the existence of `::scroll-marker-group` is dependent on the scroll container having a non-`none` value for `scroll-marker-group. <https://drafts.csswg.org/css-overflow-5/#scroll-marker-group-pseudo> Then `::scroll-marker` existence is dependent on its corresponding `::scroll-marker-group` existence (+ markup information defining the element as being a "scroll marker").

This prevents us from making `::scroll-marker` a [":has-allowed pseudo-element"](https://drafts.csswg.org/selectors/#has-allowed-pseudo-element), since its existence is determined by style, and using `:has(::scroll-marker)` would allow cyclic styling loops. This, unfortunately, means it seems hard to define examples like this:

![Image](https://github.com/user-attachments/assets/47ec4c1d-dd51-4e4a-91b5-d3347d72ef01)

Note that the scroll-markers before the :target-current one are solid white; the current and subsequent ones are partially transparent. @argyleink tried to achieve this with:

```css
.carousel li:has(~ li::scroll-marker:target-current)::scroll-marker {
  opacity: 1;
}
```

But it doesn't work because `::scroll-marker` isn't marked as being valid in `:has()`.

-------

So, question: can we make the *existence* of `::scroll-marker` (and perhaps `::scroll-marker-group`) unconditional, based just on the markup information? We'd change the wording so the *box generation* is dependent on styling as currently specified, but the pseudo-element would be treated as *existing* regardless, so we could make `::scroll-marker` a ":has-allowed pseudo-element", and Adam's code would work.

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/11600 using your GitHub account


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Received on Wednesday, 29 January 2025 18:51:13 UTC