[Groff] Composed glyphs - quick and dirty solution

[Mikhail Vidiassov]

Dear Werner,

the quesion of  composing glyphs from parts has already been discussed.

Doing composition the proper way was not considered practical due to high 
costs and low demand.
A modern font may contain instrucions on composing glyphs from parts (GSUB 
table),
but it is likely to have most of the popular glyphs precomposed.

For rarely used composed glyphs or old fonts, "ps-achar" request (from 
ps.tmac) can be used,
that creates a fall-back glyph by overprinting accent centered above the 
base glyph.
It provides reasonable quality, but "ps-achar" has to be explicitly called 
for each composed glyph.
If ps-achar is to be used once for every composed glyph from unicode in 
ps.tmac, that file will be HUGE.
But it may be enough to create fallbacks for glyphs from latin-*, in that 
case ps.tmac will not grow that much.

It would be nice to have some magic hardcoded in grops to do something 
similar to ps-achar
for composed glyphs that were really used only.

For base-3 PS fonts (Courier, Helvetica, Times) accent placement may be 
somewhat improved,
since there are hand-made tables for accent placement, that may result in 
better positions than just centering the accent.
That tables originate from second millenium attempts to "add more 
characters" to base PS fonts (ogonkify project).
If there is some interest in that - I'll do it this weekend.

                     Sincerely, Michail