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

At 05:50 PM 9/14/98 +0200, Lars Hellström wrote:

>Alan Jeffrey wrote:

>>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.

>AFSIK it's not really a matter of whether the drivers can access all glyphs
>or not, but rather a matter of which glyphs are included in the fonts. Mac
>fonts are (quite logically in most circumstances) usually set up to match
>Apple's extension of 7-bit ASCII, not Adobe's, so some glyphs in the Adobe
>set might not be included. 

The fonts themselves are identical.  Adobe text fonts have 228 `standard' 
glyphs.  You can convert the actual font file from Mac to PC format back
and forth without losing anything.  The text font does have all those
glyphs --
on any platform.   A stand-alone PS driver like DVIPS can trivially get at 
all 228 if it wants to (if DVIPS could understand the Macintosh Type 1 font 
file format).

The problem is the operating system support for scalable fonts, which on
the Mac throws away 21 of the 228 and  Windows throws away 15 of the 228.
(And if Unix had such system support it might use ISO Latin 1 which discards
even more).

>You can always set up a Quickdraw font that
>allows you to access any sufficiently small (up to 224 characters is no
>problem) subset of glyphs from a Postscript font through Quickdraw alone.
>(Doing it by hand though is about as making a TFM+VF from an AFM without
>using VPtoVF or fontinst.)

It is quite easy to do this for up to 255 characters using the Font
Manipulation Package
But now you have a `non-text' font, one which is not reencoded by the OS.
And one that will lead to problems when you send a PS job to a service bureau
since there versions of the font have not been `hard reencoded'.  And platform
portability issues as well.

Clearly the `right' solution is for the DVI viewer to work around the
operating system
limitation and allow access to all 228 standard characters.  Why should one be
prevented from using ff, ffi,ffl ligatures on the Mac if the font has them
(e.g. the
Lucida Bright fonts) just because Mac standard roman encoding doesn't
include those?

Regards, Berthold.