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[css3-fonts] em unit based on used value vs. computed value of font-size

From: Simon Sapin <simon.sapin@kozea.fr>
Date: Thu, 17 Jan 2013 15:20:56 +0100
Message-ID: <50F808C8.2040408@kozea.fr>
To: "CSS WWW Style (www-style@w3.org)" <www-style@w3.org>
Hi,

In Font Matching Algorithm, css3-text says:

> ‘font-size’ must be matched within a UA-dependent margin of
> tolerance. (Typically, sizes for scalable fonts are rounded to the
> nearest whole pixel, while the tolerance for bitmapped fonts could be
> as large as 20%.) Further computations, e.g., by ‘em’ values in other
> properties, are based on the ‘font-size’ value that is used, not the
> one that is specified.

The last sentence is in contradiction with css3-values:

> em unit
>
> Equal to the computed value of the ‘font-size’ property of the
> element on which it is used.

I think the latter is correct: the em unit should not depend on font 
matching.

-- 
Simon Sapin
Received on Thursday, 17 January 2013 14:21:23 GMT

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