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Re: Baselines (was RE: Units, font sizing, and zoom suggestion for CSS 3)

From: Bert Bos <Bert.Bos@sophia.inria.fr>
Date: Thu, 3 Feb 2000 23:24:59 +0100 (MET)
To: www-style@w3.org
Message-ID: <14489.63544.762023.29121@lanalana.inria.fr>
Erik van der Poel writes:
> Bert Bos wrote:
> It's nice that you give an example using the Q element and the LANG
> attribute, but I think we need to keep in mind that real world documents
> often mix ASCII and Japanese characters, without the use of Q and LANG.
> We need a baseline story for this too.

That's probably true, although not recommended... Does Mozilla include
a spell checker? If so, that could be an incentive for people to
properly mark-up the different languages in a document.

1) One idea I've heard to deal with this is selectors for scripts (or
alternatively for Unicode ranges). Most recently from Matthew

    :chars(U+4E00-4E1F) { baseline-identifier: ideographic }

2) Somewhat simpler is to introduce script-specific properties:

   P { baseline-identifier-ideographic: ideographic;
       baseline-identifier-latin: lower }

3) But this all has the smell of defining the obvious. Maybe the
simplest solution is to add 'auto' to 'baseline-identifier'.

[1] http://lists.w3.org/Archives/Public/www-style/1999Nov/0017.html

> > (Another name for 'lower' could be 'latin', because 'ideographic' is
> > actually lower than 'lower'...
> Hmmm, that's interesting. I don't know whether ideographic would be
> considered lower than "lower". Ken Lunde's book CJKV Information
> Processing says that East Asian characters are "optically centered"
> rather than resting on a baseline. If you look at MS Gothic on Windows,
> for example, you will see that the baseline cuts through the bottoms of
> the glyphs.

I've heard different explanations of the ideographic baseline. CSS2
indeed calls it the "central baseline"[2] so I guess we should stick
to that.

[2] http://www.w3.org/TR/REC-CSS2/fonts.html#cline

> > In combination with this, there is also a proposal for a
> > 'line-height-policy' property that can, among other things, enforce a
> > mode in which the line height throughout a paragraph remains constant,
> > despite text with different baselines or sizes.
> That sounds similar to the min-line-height and line-height-override
> stuff that we've been discussing at mozilla-layout@mozilla.org.

Any pointer?

  Bert Bos                                ( W 3 C ) http://www.w3.org/
  http://www.w3.org/people/bos/                              W3C/INRIA
  bert@w3.org                             2004 Rt des Lucioles / BP 93
  +33 (0)4 92 38 76 92            06902 Sophia Antipolis Cedex, France
Received on Thursday, 3 February 2000 17:25:07 UTC

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