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Action-902 Units of measure for 1.4.3

From: Jeanne Spellman <jeanne@w3.org>
Date: Fri, 04 Oct 2013 15:22:25 -0400
Message-ID: <524F1571.1050702@w3.org>
To: UAWG <w3c-wai-ua@w3.org>
As per my action item, I followed up on the text customization proposal 
to see what unit of measure was intended for 1.4.3 on line height 
(leading), character and word spacing.

Results:  No unit of measure was specified deliberately, because no unit 
of measure is proper usage. Examples were given of CSS and Word, which 
both accept a number without a unit of measure.

I personally disagree with this. While my typography experience is quite 
dated, I have always used a unit of measure in typography.  While this 
(no unit of measure) is allowed in CSS, the examples make clear that 
CSS2 considers no unit of measure as em. The calculation of line-height 
in CSS 2.1 is quite complex, and I think we should avoid it ourselves, 
and refer people to appropriate documentation.

References (which I think we should include in the References section of 
1.4.3 IER)
  http://www.w3.org/wiki/CSS/Properties/line-height (some useful 
language here, IMO.)
Table of all CSS properties http://www.w3.org/TR/CSS2/propidx.html
The spec for CSS3 is not complete and should not be referenced.  The 
latest working draft (for your info) is 

I propose adding a Note to 1.4.3
Note: The unit of measure will vary by the technology. For the purposes 
of UAAG 2.0, the font height should be considered to be equal to 1. The 
font width of the character 0 (or other character commonly accepted in 
the typography for that language) should be considered to be equal to 1.
Received on Friday, 4 October 2013 19:22:30 UTC

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