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Re: font-size and accents, again

From: Erik van der Poel <erik@netscape.com>
Date: Tue, 16 Nov 1999 11:05:49 -0800
Message-ID: <3831AB0D.6595C1CE@netscape.com>
To: Todd Fahrner <fahrner@pobox.com>
CC: www-style@w3.org
Todd Fahrner wrote:
> 
> Any software that second-guesses the meaning of font-size based on
> the actual extent of ascent/descent/accent is going to defeat the
> intentions of font designers.

OK, so I had to decide who to believe; either Todd Fahrner or David
Baron:

  http://www.fas.harvard.edu/~dbaron/css/fonts/sizes/

Todd seems to know a lot about font design (em and all that), and the
CSS2 spec says that one em is the font-size, so I'm inclined to believe
Todd.

On Windows, I need to decide between a negative and positive lfHeight
value. The API doc says that positive lfHeight values include any
accents above letters, but Todd says that font designers allow glyphs to
protrude outside their em, so I'm going to take the negative lfHeight.

Fortunately, this is the same as the old Netscape browser, so the new
Mozilla will be compatible with the old one and with existing content on
the Web.

Now, back to X (again). On X, the max ascent and max descent are defined
such that no glyphs protrude beyond them. On the other hand, the font's
ascent is defined as follows:

  FONT_ASCENT is an integer value (of type INT32) that gives
  the recommended typographic ascent above the baseline for
  determining interline spacing. Specific glyphs of the font
  may extend beyond this.

The font descent is defined in a similar way. So I'm going to have to
change the Unix version of Mozilla to use (font ascent + font descent)
instead of the current (max ascent + max descent).

Erik
Received on Tuesday, 16 November 1999 14:08:01 GMT

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