I'm trying to set up a contextual multiple substitution (one-to-many), but FOG 5 keeps choking on the feature file and won't generate a font. The same substitution works in VOLT for TrueType OpenType fonts, although the substitution works only in Microsoft programs, and not in Adobe programs.

In VOLT, I was able to set up the substitution as:

comma -> special_glyph comma -- when preceded by -- glyph_group

Now I'm trying to use it in a feature file (based on Adobe specs) for generating a CFF OpenType font in Fontographer 5.

Here's the basic syntax for an Adobe spec feature file:

sub [ @Glyphclass ] comma' by specialglyph comma;

Essentially, the comma should be replaced with both the specialglyph and the comma whenever the comma follows anything within the @Glyphclass. I can get the multiple substitution to work without the context, but it doesn't work with the context.

Is it possible to set up a multiple substitution with a contextual exception? In other words, the substitution always happens, except in certain contexts (ignore substitution rule)?

Would it work to use contextual chaining?

If the above is not possible with an Adobe spec feature file, is it possible to use VOLT to add OpenType layout to a CFF/PostScript .otf file made in FOG 5?

Thanks!