Encoding and mapping glyphs from an expert font

[Idris Samawi Hamid <ishamid@lamar.colostate.edu>]

[To all the font experts out there: I really need your help!! I have spent at 
least 12 hours (!) trying to make this work but to no avail.]

Dear gang,

I have two fonts (actually, lots more but let's keep it simple), one normal 
and one expert. I did the following:

1. installed the regular font with texnansi encoding. It works fine. It uses, 
say,

texnansi-myfont.map, texnansi-lm.enc

with lines like

====================================================
texnansi-raw-myfont  MyFont 4 <texnansi-lm.enc <myfont.pfb 
====================================================

2. also installed the expert font with a private encoding. Basically the same 
as 
texnansi where they share characters in common. It uses, say,

myfontx.map, myencoding.enc

with lines like

====================================================
myencoding-raw-myfontx MyFontX 4 < myfont.pfb   myencoding.enc
====================================================

3. With a view to getting characters from my expert font, I carefully studied 
as best as I could the implementation of old style figures in lmr, which 
involves mappings to cmmi10. This is what I could figure out: Activating old 
style is done by

====================================================
\usetypescript [modern][texnansi]
\usetypescript [map]   [latin-modern-os] [texnansi]

\usetypescript[latin-modern][texnansi]
\setupbodyfont[latin-modern]
====================================================

There appear to be two main things going on (but I think I'm missing 
something):

a. loading a map file:

====================================================
\starttypescript [map] [latin-modern-os] [ec,texnansi,qx,t5,pl0,il2]
  \loadmapfile[\typescriptthree-os-public-lm.map]
\stoptypescript
====================================================

Since I'm using texnansi, I looked at texnansi-os-public-lm.map . It contains 
lines like

====================================================
texnansi-lmb10 LMRomanDemi10-Regular <texnansi-os-lm.enc <lmb10.pfb
====================================================

So I designed an encoding file myfont-plus.enc almost identical to 
texnansi-os-lm.enc, containing, e.g., old style numerals from my expert font. 
I edited the myfont map files to exactly match the syntax of both

texnansi-os-public-lm.map 
and 
texnansi-public-lm.map

So for my fonts I have a total of three map files:

\loadmapfile[texnansi-myfont.map]
 % for regular font

\loadmapfile[myencoding-myfontx.map] 
% for expert font

\loadmapfile[texnansi-x-myfont.map]  
% for mapping minion reg to minion ex

>From this point I am lost. I set up my type-myfont.tex to load these maps. I 
can get myfont to work alone, and myfontx to work alone, but I cannot map  
characters from myfontx to myfont.

By the way, I still don't understand how placing, e.g., /zerooldstyle in the 
respective /zero position in an encoding file will instruct LatinModern to 
pick up the glyph from cmmi10. In, for example,

====================================================
texnansi-lmb10 LMRomanDemi10-Regular <texnansi-os-lm.enc <lmb10.pfb
====================================================

How does ConTeXt know that /zerooldstyle is to be mapped to cmmbi10?
I must be missing something....

Thnx in advance for your help
Idris

============================
Professor Idris Samawi Hamid
Department of Philosophy
Colorado State University
Fort Collins, CO 80523