Re: [csswg-drafts] [css-anchor-position-1] Back-compat of scrollable containing block for all abspos with implicit anchors (#13067)

Thinking about this some more, I'd like to re-open the resolution from TPAC because it regressed what I think is an important developer ergonomics point: previously, if you had set up the anchor bindings correctly in HTML using popover, then combining it with `position-area` was a one-liner: `position-area: bottom` hooked you up to the bottom of the anchor.

It made using HTML bindings feel more natural and automatic, feel more like a "right thing" to do -- which it is, and which we need to encourage, in order for the accessibility bindings to do their job. Now, though, authors *also* have to set `position-anchor: auto` to get this behavior, even though `position-area` on its own is enough to know that we want to use anchor positioning.

So I'd like to propose that we revisit this issue, and make sure that `position-area` values other than `none` pick up the implicit binding automatically, without requiring the author to set `position-anchor`.

One way to do this would be to have the initial value of `position-area` be something like `normal`, which computes to `none` (no implicit anchor) or `auto` (use the implicit anchor) based on whether `position-area` is set. So that's my starting proposal.

This still avoids the compat issue that caused us to introduce 'none' (absolutely positioned elements changing their containing block when a future spec update gives them a new implicit anchor).

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Received on Friday, 19 December 2025 20:49:58 UTC