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Date:         Thu, 29 Feb 1996 10:09:32 -0500
From: Michael Downes <MJD@MATH.AMS.ORG>
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Subject:      Re: Additional font dimensions for text fonts
Status: R

J"org Knappen wrote:

> This a request for feedback, which additional font dimensions the ec text
> fonts should have. For nice typesetting, which font dimensions are usefull?
> How could they be applied (e. g. in LaTeX3)?
>
> The dc fonts currently contain 6 additional font dimensions, namely
> def font_character_set expr x = fontdimen  8: x enddef;
> def font_baselineskip  expr x = fontdimen  9: x enddef;
> def font_acc_height    expr x = fontdimen 10: x enddef;
> def font_cap_height    expr x = fontdimen 11: x enddef;
> def font_asc_height    expr x = fontdimen 12: x enddef;
> def font_rule_thickness expr x = fontdimen 13: x enddef;

Here are a set of fontdimen associations that I have used on occasion. I
use the capheight and similar dimens to get precise size and placement
of running heads in relation to the text block and the type block. (I
prefer to stuff running heads into a box of depth 0 and height
capheight, and don't really need the other fontdimens, but perhaps other
people will have different opinions about ideal values for running head
height (and topskip).)

I haven't needed digitwidth yet, I only included it when setting up this
group of fontdimens because I saw it in ISO/IEC 9541-1:1991(E) (font
standard) and thought it might turn out to be useful some day for
special table applications.

I didn't include ideal line-spacing in this group when I set it up,
because unlike the other dimens here, that cannot be calculated by
measuring in TeX (unless you want to use an arbitrary formula based on,
let's say, x-height).

Regards, Michael Downes (mjd@ams.org)

%% capheight
%    We assume for common sense' sake that symbol fonts and extension
%    symbol fonts do not require \capheight, \descenderdepth, etc.
%    because they should not contain alphabets (even though cmsy
%    currently does.) Therefore we use fontdimens 8--11 for alphabetic
%    fonts to supply \capheight etc., rather than putting them in
%    \fontdimens 23 and up.
%
\def\capheight{\fontdimen8 }

%% ascenderheight
%    Ascender height is usually the same as \capheight but not always.
%    For some purposes we may want to use \capheight regardless of
%    \ascenderheight (e.g. in all-uppercase text), while for other
%    purposes we may want to use the max of \capheight and
%    \ascenderheight. NOTE: only letters; does not include things
%    like parentheses.
%
\def\ascenderheight{\fontdimen9 }

%% descenderdepth
%    Maximum depth of descenders. Does not include things like
%    parentheses.
%
\def\descenderdepth{\fontdimen10 }

%% fontmaxheight
%    Max height and max depth include things like parentheses.
%
\def\fontmaxheight{\fontdimen11 }

%% fontmaxdepth
%    Maximum depth of all characters.
%
\def\fontmaxdepth{\fontdimen12 }

%% digitwidth
%    Maximum width of all digit characters 0--9. Commonly all the
%    widths are the same = .5em, in order to give nice alignment in
%    tables.
%
\def\digitwidth{\fontdimen13 }