Re: [csswg-drafts] [css-anchor-position][other] Handling popover default styles (#10258)

The CSS Working Group just discussed `[css-anchor-position][other] Handling popover default styles`.

<details><summary>The full IRC log of that discussion</summary>
&lt;emilio> fantasai: issue is that popover UA default has `margin: auto` in it<br>
&lt;emilio> ... margins win over alignment<br>
&lt;emilio> ... so when you have a popover and you set position-area on it you put it in the right area but then it gets centered in that<br>
&lt;emilio> ... which is not likely what you want<br>
&lt;emilio> ... this has tripped up a number of people<br>
&lt;emilio> ... our original idea was to introduce a special alignment value<br>
&lt;emilio> ... that would center except if you have position-area<br>
&lt;emilio> ... when I implemented it I noticed that we had a bunch of tests that would set margin: 0<br>
&lt;emilio> ... which is likely to come up<br>
&lt;emilio> ... which means we need another way of doing this<br>
&lt;emilio> ... I came up with several ideas<br>
&lt;emilio> ... we could condition them on having the special keyword for alignment vs. not<br>
&lt;emilio> ... or if position-area is not none you can't use auto margins<br>
&lt;emilio> ... I don't particularly want to do this because I think position-area into the center of an anchor might be reasonable<br>
&lt;emilio> ... so it'd be surprising if they don't work<br>
&lt;emilio> ... so we could say if position-area is not none or center then disable auto margins, then disable then<br>
&lt;emilio> ... or span-all too perhaps<br>
&lt;emilio> ... but the ones on an asymmetric position with the anchor wouldn't<br>
&lt;emilio> ... the other thing is that we could do this always or only if we do the self-alignment legacy value thing<br>
&lt;emilio> ... in which case it'd be mostly popovers<br>
&lt;emilio> q+<br>
&lt;emilio> astearns: ian likes your first option best<br>
&lt;emilio> ... I'm a bit concerned about the possibility of going this route only if the alignment is `dialog`<br>
&lt;emilio> ... makes copying styles to something else not work<br>
&lt;astearns> ack emilio<br>
&lt;fantasai> emilio: similar concern, be weird to have a random abspos that works and when you put it on popover it doesn't work or vice versa<br>
&lt;fantasai> emilio: so, if we don't want this difference, we don't need this special keyword, right?<br>
&lt;fantasai> fantasai: yeah, it's only here to solve this problem<br>
&lt;fantasai> emilio: then if we need to special case it for compat, we may as well not have the special keyword<br>
&lt;emilio> fantasai: if we're not going to condition it on `dialog` I'd lean towards #3<br>
&lt;emilio> ... I think they won't try to use them in the side tracks<br>
&lt;emilio> ... but span-all and co seems reasonable<br>
&lt;fantasai> ... and would be surprising if it doesn't work<br>
</details>


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Received on Wednesday, 8 October 2025 17:01:10 UTC