Re: [csswg-drafts] [css-multicol] Containing block of column spanners (#5612)

The CSS Working Group just discussed `containing block of column spanners`, and agreed to the following:

* `RESOLVED: CB chain goes straight from spanner to the multicol container`

<details><summary>The full IRC log of that discussion</summary>
&lt;TabAtkins> Topic: containing block of column spanners<br>
&lt;TabAtkins> github: https://github.com/w3c/csswg-drafts/issues/5612<br>
&lt;TabAtkins> rachelandrew: Good details in the issue<br>
&lt;TabAtkins> rachelandrew: We dont' have interop<br>
&lt;TabAtkins> rachelandrew: If you have abspos in a column spanner, not clear the what containing block should be<br>
&lt;TabAtkins> rachelandrew: Three different options currently<br>
&lt;TabAtkins> rachelandrew: In the issue it came down that probably either #2 or #3 would be most likely, either viewport (WebKit and EdgeHTML) or the column spanner itself<br>
&lt;Rossen_> q?<br>
&lt;TabAtkins> rachelandrew: I suspect authors would assume the spanner is the containing block, or at least would want that ability<br>
&lt;TabAtkins> rachelandrew: Option 1 is probablematic anyway<br>
&lt;TabAtkins> rachelandrew: In gecko it would be harder to implement option 2<br>
&lt;TabAtkins> rachelandrew: So it's between 2 and 3, viewport and spanner<br>
&lt;Rossen_> q<br>
&lt;Rossen_> q+<br>
&lt;astearns> ack fantasai<br>
&lt;TabAtkins> fantasai: I think option 3 is a little weird - it doesn't ahve relpos<br>
&lt;Rossen_> q-<br>
&lt;TabAtkins> fantasai: And so unless there's something particularly interesting happening on, like transform, elements dont' trap abspos unless they're relpos<br>
&lt;TabAtkins> fantasai: So I'm totally fine with skipping the fragmenting grandparent<br>
&lt;TabAtkins> fantasai: But I think it woudl be weird to stop at the spanner and not go up to the multicol itself if *that* has relpos<br>
&lt;TabAtkins> fantasai: and otherwise fall up to the ICB<br>
&lt;TabAtkins> iank_: Chrome broadly agrees with that<br>
&lt;TabAtkins> florian: I was thinking as well<br>
&lt;TabAtkins> Rossen_: EdgeHTML as well, the spanner is nothing special, you just walk the ancestor chain as normal until you find a positioned element<br>
&lt;TabAtkins> florian: That's a little different from what fantasai described, i think<br>
&lt;TabAtkins> florian: If you have a relpos parent of the spanner, if you go by ancestry in the tree, that would capture the abspos<br>
&lt;TabAtkins> florian: elika was talkinga bout skipping past that straight to the multicol, to avoid fragmentation issues<br>
&lt;TabAtkins> iank_: Part of the problem is that the spanner isn't really positioned in flow, it's positioned by the multicol, so option 2 is kinda in that direction<br>
&lt;TabAtkins> fantasai: I think from an author's perspective, yeah, skipping from spanner to multicol would make the most sense since the spanner isn't fragmented<br>
&lt;TYLin> q+<br>
&lt;TabAtkins> fantasai: That's option 2, yeah; option 3 makes the spanner the containing block regardless of its 'position'<br>
&lt;TabAtkins> fantasai: So the CB chain should go spanner -> multicol -> normal ancestry from there<br>
&lt;TabAtkins> florian: I'm confused, option 2 says viewport<br>
&lt;TabAtkins> astearns: if you read the text it goes into more detail<br>
&lt;astearns> ack TYLin<br>
&lt;TabAtkins> fantasai: there's no relpos in the example, that's why it goes up to viewport<br>
&lt;astearns> ack emilio<br>
&lt;TabAtkins> TYLin: I think option 2 is best, Gecko is buggy in edge cases<br>
&lt;TabAtkins> astearns: So it sounds like option 2 has consensus, cb chain goes spanner -> multicol and then normal from there<br>
&lt;TabAtkins> astearns: objections?<br>
&lt;chris> q+<br>
&lt;TabAtkins> RESOLVED: CB chain goes straight from spanner to the multicol container<br>
&lt;astearns> ack chris<br>
</details>


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Received on Friday, 23 October 2020 14:15:13 UTC