Path: utzoo!attcan!uunet!decwrl!wuarchive!cs.utexas.edu!rice!uw-beaver!zephyr.ens.tek.com!tektronix!reed!barry
From: barry@reed.UUCP (Barry Smith)
Newsgroups: comp.sys.mac.system
Subject: Re: Bizarre problem with a large math font
Summary: QuickDraw bugs with "funny" characters
Keywords: font, large characters
Message-ID: <15235@reed.UUCP>
Date: 26 Jul 90 05:24:56 GMT
References: <1990Jul23.161753.13159@ra.src.umd.edu>
Reply-To: barry@reed.UUCP (Barry Smith)
Distribution: na
Organization: Blue Sky Research, Portland OR
Lines: 49

From a letter to Mr. Loncaric:

Thank you for your comments on our Textures software. I'm
afraid that I can not offer much assistance with the printing
and display of the mathematical fonts at large sizes, although
I may be able to explain the cause of the problem.

The problem is, as far as we can determine, due to errors in
the Macintosh system software, specifically the QuickDraw
graphic display language.  In certain cases, especially with
larger point sizes, fonts that contain characters that differ
from ``normal'' placement are drawn incorrectly or
incompletely. We have seen this problem with several fonts, at
a variety of sizes and on a wide selection of devices;
different versions of the system software will sometimes
display varying examples of the problem.

Some examples from fonts CMEX10 and CIRCLE may help explain
the sort of characters that are involved with this problem. 
In the font CMEX10, the \TeX\ math extension font, the
characters are entirely descent with no ascent (they hang
below the reference point on the type baseline), and in some of
the characters (e.g., the integral signs) the character image
is wider than the character advance width, or, in other words,
some characters may overhang the reference point of the
adjacent character.  In the CIRCLE font used in \LaTeX, the
reference points and character widths of the circle sections
are placed so as to make alignment easy; this results in some
character images that are entirely to the left of their
reference points.  Yet another type of problem can be caused
by characters that have a zero advance width, or ``no width'',
such as the slash used for negation of various math symbols.

It is our belief that our fonts are well-formed, and that the
problems you (and we) are experiencing are entirely due to
errors in the Apple system software.  We have made various
people at Apple aware of these problems on several occasions
in the past three years.  I can only hope that these problems
will be corrected in a future release of the Apple software,
and offer any assistance you may desire should you wish to
pursue this problem with Apple yourself.

If you have access to a PostScript laser printer, please be
aware that problems of this sort do not occur on PostScript
printers, in our experience.

---
Barry Smith, Blue Sky Research
barry@reed.edu