Re: [csswg-drafts] [css-overflow-5] Creating scroll-marker groups within which to select an active marker (#10916)

Based on the previous discussion and resolution, I propose we add a `scroll-marker-contain: auto | none` property for grouping scroll-markers. An element having `scroll-marker-contain: auto` is a [scroll marker group container](https://drafts.csswg.org/css-overflow-5/#scroll-marker-group-container) establishing a group of all of the scroll marker elements for which this is the nearest ancestor scroll marker group container.

Having a property on an ancestor rather than having the markers themselves name a group allows for easy re-use. E.g. you can have multiple group containers throughout the page re-used in various components without needing to give them unique names. Name scoping would be possible, but then we would need an ancestor property to scope the name anyways.

We might be able to explain the [pseudo grouping behavior](https://drafts.csswg.org/css-overflow-5/#scroll-marker-grouping) by saying that the UA stylesheet includes:
```css
::scroll-marker-group {
  scroll-marker-contain: auto !important;
}
```

Note that when [scrolling](https://drafts.csswg.org/css-overflow-5/#active-scroll-marker) we would still set the [last-focused element](https://open-ui.org/components/focusgroup.explainer/#last-focused-memory) of an ancestor focusgroup to the selected marker so that when used with focusgroup the active marker becomes the tab stop in a focus group with all elements having a `tabindex` of -1.

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Received on Tuesday, 29 October 2024 19:46:40 UTC