font-size and accents, again


I'm still concerned about CSS's "font-size". The CSS2 spec and several
members of the CSS community seem to indicate that the CSS font-size
includes not only the descenders and ascenders, but also any accents
that might be placed on top of glyphs (e.g. capital E with acute

However, I have also seen a couple of sources that give a different
meaning for the "point size" of a font. For example, "The PostScript
Font Handbook" says that "Point size is measured from the top of the
ascender to the bottom of the descender." It says that the ascender is
"the part of a lowercase letter, such as in b or h, that rises above the
x-height", while the descender is "the part of a character that extends
below the baseline, as in g or p".

Another source is the Windows API documentation. It says that the height
of a font with a certain point size can be specified as:

  lfHeight = -MulDiv(PointSize, GetDeviceCaps(hDC, LOGPIXELSY), 72);

When lfHeight is negative, the font mapper uses the "character height"
rather than the "cell height", where cell height is defined to be
character height plus "internal leading", which is where accents occur:

Now, these discrepancies wouldn't bug me so much if we could somehow
hide all of this from the user, but there is one area where I believe we
have to reveal something to the user, and that is the font preferences
dialog, where we allow users to set their default font size.

The old Netscape UA code base used negative lfHeight values, so people
accustomed to that UA may have come to expect the point size to mean the
unaccented height of the font. If the new Mozilla code base suddenly
switches to positive lfHeight values (to comply with CSS2), the height
will include accents, so "12 point Times" in the new Mozilla becomes a
smaller font than "12 point Times" in the old Netscape UA.

Such a change could confuse users who are viewing text on a screen, as
well as users who print documents on a high-resolution printer.

Even if we disregard the users of Netscape's old UA, there clearly are
people on this planet who think that point size means unaccented height.
The PostScript Font Handbook and Windows API documentation are just 2
pieces of evidence.

So, what words of advice do you offer?


Received on Tuesday, 16 November 1999 02:54:09 UTC