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[csswg-drafts] [css-multicol] How do elements between column-span and its multicol ancestor appear around the span

From: L. David Baron via GitHub <sysbot+gh@w3.org>
Date: Fri, 03 Mar 2017 23:45:41 +0000
To: public-css-archive@w3.org
Message-ID: <issues.opened-211832162-1488584740-sysbot+gh@w3.org>
dbaron has just created a new issue for 
https://github.com/w3c/csswg-drafts:

== [css-multicol] How do elements between column-span and its multicol
 ancestor appear around the span ==
The [definition of 
`column-span`](https://drafts.csswg.org/css-multicol/#column-span) 
doesn't appear to say anything about what happens to the elements that
 are ancestors of the element with `column-span: all` but descendants 
of the "nearest multicol ancestor in the same block formatting 
context" (i.e., the element that establishes the columns being 
spanned).

What happens to the backgrounds, padding, borders, and margins of 
these elements where the column span interrupts them?  Do they appear 
as though they were a block ancestor of the column-spanning element?  
(What if they were inline elements?)  Does relative positioning on 
these elements apply to the column-spanning element?  Transforms?  
etc.

This situation is in some ways analogous to the situation that happens
 when an inline contains a block, which is [defined reasonably 
thoroughly](https://drafts.csswg.org/css2/visuren.html#anonymous-block-level)
 in CSS Level 2, except that this situation is a bit more general 
since the ancestors being split can be either inlines or blocks, 
whereas in the block-in-inline situation the split ancestors are only 
inlines.

I'd note that failing to display the background of an ancestor behind 
the column-spanning element could violate accessibility expectations 
related to colors and backgrounds.

What do existing implementations do? (IIRC, Gecko is the last engine 
to implement `column-span`, which would have made me expect the spec 
to be in better shape than it appears to be.)

/cc @tabatkins @gregwhitworth @neerjapancholi

Please view or discuss this issue at 
https://github.com/w3c/csswg-drafts/issues/1072 using your GitHub 
account
Received on Friday, 3 March 2017 23:45:48 UTC

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