W3C home > Mailing lists > Public > www-style@w3.org > May 2010

Re: Questions about 'column-span'

From: Håkon Wium Lie <howcome@opera.com>
Date: Sat, 22 May 2010 23:38:13 +0200
Message-ID: <19448.20165.837248.507500@gargle.gargle.HOWL>
To: Bert Bos <bert@w3.org>
Cc: "www-style@w3.org list" <www-style@w3.org>
Bert Bos wrote:

 > > (1) Are there any implementations of this property yet?  My own vote
 > > would be for cutting it, since the desired effect can be pretty
 > > easily obtained by just wrapping the contents underneath headings in
 > > a block and putting multi-column styles on those content blocks.
 > Usually there is no such element, though. A typical mark-up would be
 >     <section>
 >       <h>The title</h>
 >       <p>...
 >       <p>...
 >     </section>
 > with
 >     section {columns: 2}
 >     h {column-span: all}

This is one good use caser for column-span: to be able to apply
column-span formatting (which is quite common) to existing markup.

The other, more advanced, use case is for us to be able to set an
integer value on 'column-span' in the future. But that's for the
future to decide.

 > > My own proposal for resolving this would be that [..] column-span
 > > can only apply to objects within the same block formatting
 > > context as the multicol block. That prevents objects inside
 > > overflow:hidden blocks or inline-blocks from being considered.
 > That makes sense. The columns that 'column-span' refers to are those of 
 > the root of the current block formatting context. (If that root is not 
 > a multi-column element, then there are no columns to span 
 > and 'column-span' has no effect.)


 > > (3) Can the column-span element be an inline?  I'm inclined to say
 > > that it has to be a block-level element.  It seems weird to me to
 > > break an inline out of flow like that (that could possibly span
 > > multiple lines).  You'd have to at the very least make an anonymous
 > > block to wrap the inline anyway.
 > It obviously has to be block-level, but that leaves two possibilities:
 >   - 'column-span <> 1' *makes* the element into a block, or
 >   - 'column-span' only *applies* to block-level elements.
 > The second seems by far the easiest to understand and is sufficient, I 
 > think.
 > In some case you would have to add a 'display: block' to make 
 > the 'column-span' work, e.g. in this case:
 >     IMG {column-span: all; display: block}
 > But that is not unusual for IMG.

This seems like a reasonable proposal. The draft currently says:

  Applies to: 	static, non-floating elements

We should probably change that to:

  Applies to: 	block-level elements

And add some examples in the specifications that show how it only has
effect in the current formatting context.

 > > Do their margins collapse with one another?
 > I'd say:
 > (a) No, margins don't disappear.
 > (b) Is the question if the H2 and the P in this fragment collapse their 
 > margins?
 >     <DIV STYLE="columns: 2">
 >       <H2 STYLE="column-span: all; margin-bottom: 1em">HHHH...</H2>
 >       <P STYLE="margin-top: 1em">PPPPPPPPP...
 >     </DIV>
 > In other words, does it look like the left or the right image?
 >     PPPPPPP  PPPPPPP                    PPPPPPP
 > I think I prefer the left image, i.e., the margins do collapse between 
 > spanning elements and their non-spanning siblings.

Yes. Text and an example to this effect should be added. 

              Håkon Wium Lie                          CTO °þe®ª
howcome@opera.com                  http://people.opera.com/howcome
Received on Saturday, 22 May 2010 21:38:50 UTC

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