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Re: position of baseline relative to em square

From: Nick Nussbaum <nickn@seanet.com>
Date: Tue, 30 Nov 1999 19:03:53 -0800
Message-ID: <000701bf3ba8$b46c3c80$6209070a@nickn0>
To: <www-font@w3.org>
Cc: "Todd Fahrner" <fahrner@pobox.com>
Neither is correct.
The baseline is a function of the script. Han and Math center character
center the baseline and the em square would be correct. Latin fonts use an
assymmetric baseline. Since some fonts support multiple scripts, the safest
thing would be to provide a font property with a value for each script. This
is why there's a BASE table in Truetype Open, although default values can be
calculated for older formats based on the script.
Note that characters actually are aligned optically to the baseline. See
http://www.microsoft.com/typography/developers/fdsspec/default.htm
for a nice discussion of some of the complexities.
If you had to choose one, it would be better to use Em Square rather than
Bounding box. Bounding box means that two fonts of the same typeface  with
different character sets might  align differently because one had Uppercase
accents.

<The views expressed here are mine and not necessarily those of my
employers.

----- Original Message -----
From: Todd Fahrner <fahrner@pobox.com>
To: <www-font@w3.org>
Sent: Tuesday, November 30, 1999 11:46 AM
Subject: Re: position of baseline relative to em square


> At 10:11 AM -0800 11/30/99, Erik van der Poel wrote:
>
> >I'd like some opinions. Do any of you believe that CSS should specify
> >that text should be centered in its inline box according to the font's
> >em square? Or should it be centered with respect to its bounding box?
>
> My vote's for em square. I think this will more likely produce
> "optically centered" results than bounding box.
>
> www-font regulars: this thread adjoins a discussion in www-style,
> "font-size and accents, again", which has perhaps suffered from lack
> of font-tech smarts. You might wish to review the archives and help
> rescue CSS-2 from certain vagaries.
>
> --
> Todd Fahrner
>
>
Received on Tuesday, 30 November 1999 22:01:23 UTC

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