List cases for a cap height unit

Related tracker issue: http://www.w3.org/Style/CSS/Tracker/products/8
David Baron suggested adding a "cap height" unit in
<http://lists.w3.org/Archives/Public/www-style/2008Nov/0552.html>,
which represents the height of a capital letter.  This is analogous to
the "ex" unit, which is generally the height of a lowercase letter.

Some use-cases:

1. Providing images for mathematical symbols that are not yet in
Unicode, that should be the size of the text it's embedded into.

2. Providing smiley images that should be the size of the text they're
embedded into.

3. Providing a sparkline (miniature, info-rich graph meant to be
interleaved with text) that's baseline aligned and as tall as possible
without disrupting the height of the line.


Some objections noted on the recent telcon were that this may be
somewhat less useful for non-Latin (or related) scripts.

For Japanese and other sinographic scripts, the 'em' unit already
plays a similar role - the height of text is typically sized according
to the em box in such scripts.

Elika said that it would play nicely with Arabic, better than the 'ex'
unit, since Arabic has a useful notion of "capital letter height" that
serves the same role as it does in Latin scripts.

Questions were brought up over Indic scripts and Thai.  Nobody on the
call was certain whether these scripts had a useful notion of "capital
letter height", and if they did, if this was useful when combined with
vertical-align in the same way that it is for Latin scripts.

~TJ

Received on Wednesday, 26 October 2011 16:38:28 UTC