[csswg-drafts] [css-anchor-position] Ability to provide multiple anchor-elements to try for position-anchor property and other anchor functions (#10409)

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

== [css-anchor-position] Ability to provide multiple anchor-elements to try for position-anchor property and other anchor functions ==
Right now we can provide only one `<anchor-element>` to the `position-anchor` property, and only one ``

However, multiple anchor features like `anchor()` and `anchor-size()` have a fallback argument, which allow us to try multiple anchors in succession like `anchor(inside --foo, anchor(inside --bar, anchor(inside --baz)))`, which allows us to get the first anchor that we can attach to. However, writing it in this way is rather cumbersome.

What if we could:

1. Allow passing `<anchor-element>` to the `position-anchor`, so the element will choose the first valid anchor from the list to use as the default one.
2. Allow passing multiple `<anchor-element>` to the `anchor()` and `anchor-size()`, also allowing to simplify the selection of the anchor for these cases.

Open questions:

- Should we use `<anchor-element>#` or `<anchor-element>+`? `anchor()` and `anchor-size()` have a side/size alongside the value plus a fallback after a comma. So if we'd want to allow using multiple anchors, it could look like `anchor(inside --foo --bar --baz, 10px)`. For `position-anchor` we could probably use commas, but should we be consistent with the `anchor` functions?
- Thinking a bit more about it: I don't like the `--foo --bar --baz`, as it is hard to understand that this is a list of fallbacks. First thing I though of is to do something like `first-valid(--foo, --bar, --baz)`, although we probably don't want to have a conflict with https://github.com/w3c/csswg-drafts/issues/5055, but I wonder if there are other places in CSS where we could have a similar case, where we want to use some reference, and potentially try multiple of them. If so, then having a more general function could be useful.

Please view or discuss this issue at https://github.com/w3c/csswg-drafts/issues/10409 using your GitHub account


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Received on Sunday, 9 June 2024 14:54:01 UTC