Re: [csswg-drafts] [css-multicol] Margin collapsing does not make sense with column-spans.

The CSS Working Group just discussed `Margin collapsing does not make sense with column-spans`, and agreed to the following:

* `RESOLVED: margins between adjacent spanners do collapse`
* `RESOLVED: margins between spanners and any other non-spanning boxes do not collapse`

<details><summary>The full IRC log of that discussion</summary>
&lt;heycam> Topic: Margin collapsing does not make sense with column-spans<br>
&lt;heycam> github: https://github.com/w3c/csswg-drafts/issues/2203<br>
&lt;heycam> dbaron: I think there are a few different things going on<br>
&lt;heycam> ... I'm not sure which we've already solved<br>
&lt;heycam> ... one is that one thing, at the time, nothing said that the columns inside a multicol create BFCs<br>
&lt;heycam> ... the underlying question is can margins on column spans collapse<br>
&lt;heycam> ... 2 questions under that<br>
&lt;heycam> ... 1 is can the margin on a column span collapse with another column span right next to it<br>
&lt;heycam> ... that one, we could maybe argue about<br>
&lt;heycam> ... there are believable arguments on both sides<br>
&lt;heycam> ... other question is can a margin on a column span collapse the first thing in the multi col part in the col span (??)<br>
&lt;heycam> ... last time we looked at hte spec, it looked like it could collapse<br>
&lt;heycam> florian: the spec is vague enough to read it that way<br>
&lt;heycam> dbaron: the spec defines when margins can collapse, and nothing says they don't<br>
&lt;fantasai> I like Morten's proposal in https://github.com/w3c/csswg-drafts/issues/2203#issuecomment-431695940<br>
&lt;heycam> ... I think I would strongly like to define that the margins of column spans don't collapse with margins of things in the columns<br>
&lt;heycam> ... then there's the qn of can one column span's margin collapse with another<br>
&lt;heycam> dbaron: there's a bunch of text in the issue I haven't looked at recently<br>
&lt;heycam> fantasai: Morten posted a proposal, we don't have a strong definition of the multicol layout model in the spec<br>
&lt;heycam> ... he proposes a model for exactly how the different formatting contexts interact<br>
&lt;heycam> ... I think it makes a lot of sense. it gets us what dbaron said, but does that by defining the multicol container as being a BFC, and for it to contain column span and column containers, which are siblings, and they are laid out in a BFC, so the margins between spanners collapse<br>
&lt;heycam> ... but the spanners define their own BFCs so they don't collapse with things in the columns<br>
&lt;heycam> ... it's quite straightfrward and we should adopt it<br>
&lt;heycam> florian: I believe we've previously resolved that does say hte margins between siblings spanners collapse, and that spanners and content in columns do not<br>
&lt;heycam> ... at least in examples<br>
&lt;heycam> Rossen: we could defer this to later on after people have had a chance to read it<br>
&lt;heycam> florian: or I suggest we resolve on spanners collapsing with each other, but not content in the column<br>
&lt;heycam> ... but not on the mechanism to achieve this<br>
&lt;heycam> ... which we can do later<br>
&lt;heycam> RESOLVED: margins between adjacent spanners do collapse<br>
&lt;heycam> RESOLVED: margins between spanners and any other non-spanning boxes do not collapse<br>
</details>


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Received on Monday, 22 October 2018 10:30:11 UTC