[fonts] TT instructing/hinting

[Gregg Reynolds <gar at arabink dot com>]

Hi,

I'm thinking about tackling hinting for the khotot project.  I assume 
the Arabeyes fonts are currently not hinted extensively, and I think a 
well-hinted set of open source (preferably GPL) Arabic fonts is a high 
priority.

Here's what I have in mind; please let me know if you think this 
approach makes sense.

1.  Editing.  I used to like to program in assembler and I love emacs, 
so I'm thinking to get started I'd like learn the TT Instruction set and 
hint a few glyphs directly in "TT Assembler".  I figure that's the only 
way to really understanding instructing.  I can write an instruction 
program using the mnemonics from the TT technical spec, but I'm not sure 
how to compile into an actual program to be added to a font.  Later on 
I'll use (or at least test) TTIComp from 
http://home.kabelfoon.nl/~slam/fonts/, but it uses a higher-level 
language (AFAIK) and rather than TT Assembler.  Can anybody help me find 
the right tools to do this?

2.  Previewing.  I'm not sure what the best tools are to view a glpyh at 
a certain point size and device resolution in order to test hinting.  It 
seems to me it would be a Good Thing to see and "exploded" view showing 
the pixel grid, the scaled (non-gridfitted) outline, and the gridfitted 
bitmap in one view.  See page 17 of the TT Tech Spec. Rev. 1.66 for an 
example.

Ideally the process would work like this.  I have a TT font with 
outlines only; I edit a TT hinting program for a glyph in emacs; I 
compile the program in emacs; a successful compile launches a previewer 
that will show me the hinted result.  Repeat cycle.

3.  Licensing.  It looks to me like the font (outlines) and hinting 
programs can be licensed separately.  A hinted glyph is a combination of 
an outline and a TT Instruction program.  The program could be 
distributed separately from the outline.  Technically speaking, then you 
could say that using the hints for a font does not constitute modifying 
the font.  I think.  I bring this up because, if I wrote hints for a GPL 
font like arabeyes_qr_meor, I would want them to be available for use 
for Meor's other fonts in case he chooses another license.  Plus, a 
fully documented hint program for one BEH glyph should work as a useful 
model for BEH in other fonts, so I would want to distribute the hint 
program in source code form, whether as native TT Assembler or in a 
higher lever language like the one used for TTIComp.

FYI I have a copy of Fontlab but it doesn't look to me like it is the 
best tool to use for hinting.  Maybe later, after I've mastered the 
instruction set.

What say ye?

-gregg