W3C home > Mailing lists > Public > www-font@w3.org > October to December 1999

Re: position of baseline relative to em square

From: Erik van der Poel <erik@netscape.com>
Date: Tue, 30 Nov 1999 10:11:34 -0800
Message-ID: <38441356.308332B3@netscape.com>
To: David Lemon <typenerd@slip.net>
CC: www-font@w3.org
David Lemon wrote:
> Although not very clearly specified, the (absolute values of the)
> WindowsTypographicAscent and WindowsTypographicDescent in the OS/2 table
> should sum to the em square height, positioning the baseline in the em
> square.

Where did you find the names "WindowsTypographicAscent" and
"WindowsTypographicDescent"? (Which spec(s) do you use?)

I know of 2 specs, TrueType and OpenType:


In these specs, I found the names "sTypoAscender" and "sTypoDescender".
I suppose these are the fields you're referring to?

I had a look at these fields in Times New Roman on NT4, and found that
they don't sum to the em square height.

> I can't guarantee the general case, but can state that Adobe's
> OpenType fonts do exactly that.

So, I guess some fonts get it right, others wrong.

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?


Received on Tuesday, 30 November 1999 13:14:25 UTC

This archive was generated by hypermail 2.4.0 : Friday, 20 January 2023 20:16:55 UTC