Re: [csswg-drafts] [css-overflow-5] Giving ::scroll-marker-group a name (and optionally text) (#12176)

> To my knowledge, slots are currently only used within shadow DOM, so extending that model to UA pseudo-elements like ::scroll-marker-group would be new?

This is how the `<details>` element works under the hood. It is effectively:

```html
<details>
  <template shadowrootmode="secret-browser-mode">
    <slot secret-browser-part="summary"><div>Details</div></slot>
    <slot secret-browser-pseudo="::details-content"></slot>
  </template>
</details>
```

(The `secret-browser-*` bits are made up for demonstration).

This means if you make a `<details>` element with no summary, you get a summary with contents of the default slot (`<div>Details</div>`). We could do the same for scroll-marker-group whereby an element that becomes a scroll container gets an effective shadow dom of:

```html
<template shadowrootmode="secret-browser-mode">
  <slot secret-browser-part="scroll-marker-group" secret-browser-pseudo="::scroll-marker-group"><!-- some default html here --></slot>
</template>
```

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Received on Thursday, 11 September 2025 19:18:01 UTC