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Re: How can I check for the existence of a glyph in TeX?

Berthold K.P. Horn wrote:

> Argh!  My TeX tells me right away about missing glyphs (on screen and in
> the log file) and gives me the context so I can tell where the problem is!

This works because you use a TeX implementation where there's only one
notion of `does the glyph exist'.

On some systems (notably MacOs) whether a glyph exists or not depends on
which driver you use (eg PostScript drivers have access to all glyphs,
but QuickDraw drivers don't).  So the notion of `missing glyph' has to
be put off to the driver in some cases.

Another case in point: some drivers can fake a dotless j, some can't. 
So the TFMs include a slot for dotless j of the appropriate dimensions,
and it's up to the driver as to whether the glyph exists or not.

This is why the TFMs contain dimension info for glyphs which the driver
may not know about.

The alternative would be shipping different TFMs for each driver, but
this would cause even more of a nightmare than the current situation.

Alan Jeffrey,  Visiting Associate Professor, CTI, DePaul University, USA
Lecturer in Theoretical Computer Science, COGS, University of Sussex, UK
ajeffrey@cs.depaul.edu      alanje@cogs.susx.ac.uk       +1 312 362 8322