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Re: [css3-multicol] Feedback

From: Håkon Wium Lie <howcome@opera.com>
Date: Fri, 16 Oct 2009 00:36:04 +0200
Message-ID: <19159.41940.878594.139859@gargle.gargle.HOWL>
To: Sylvain Galineau <sylvaing@microsoft.com>
Cc: "www-style@w3.org" <www-style@w3.org>
Sylvain Galineau wrote, on 14 Jul (!) 2009:

 > In section 4, Column gaps and rules [1]:
 > 
 > "Column rules are only drawn between columns that have content."
 > 
 > Assuming column 2's entire content did not fit e.g. an image and
 > needs to overflow to the next page, I assume column 2 is considered
 > to have content in this case.
 > 
 > [1] http://www.w3.org/TR/2009/WD-css3-multicol-20090630/#column-gaps-and-rules

It's a good question. Two more general questions, which the spec also
should answer, are:

  1) what are the endpoints of a column rule?
  2) between which columns should a rule be drawn?

It seems that we currently have three implementations: Gecko, Prince,
AntennaHouse. All three answer question 1) in the same way: the
endpoints are positioned on the content edge. However, I don't think
this is optimal. Consider this screen shot:

  http://people.opera.com/howcome/2009/tests/column-rule-ss.png

>From a visual/optical point of view, the column rules stick up too
high. This is due to the line-height being bigger than the height of
the glyphs. A better (albeit more complex) rule would be to base
computations on the font in the top/bottom lines, rather than the
content box.

For question 2), implementations differ. Gecko and AntennaHouse do not
display column rules if there isn't content on both sides. For
example, if an element has three columns, but only one word, there
will only be content in the first column. In this case, Gecko and
AntennaHouse will not display column rules at all. Prince, however,
will always display all column rules.

In all three implementations, all column rules of an element always
have the same length. This seems like a principle worth keeping.

Here's a test case:

  http://people.opera.com/howcome/2009/tests/column-rule.html

Comments welcome.

-h&kon
              Håkon Wium Lie                          CTO °þe®ª
howcome@opera.com                  http://people.opera.com/howcome
Received on Thursday, 15 October 2009 22:36:44 GMT

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