I'm having trouble with ligatures

[budgie]

I'm having trouble with ligatures for my font. The feature file looks like this, which seems to satisfy the requirements

# Ligatures: ffi ffl fi fl ff fj fb fh fk

languagesystem DFLT dflt;
languagesystem latn dflt;

feature liga {

   sub f f i by f_f_i;
   sub f f l by f_f_l;
   sub f i by f_i;
   sub f l by f_l;
   sub f f by f_f;
   sub f j by f_j;
   sub f b by f_b;
   sub f h by f_h;
   sub f k by f_k;

} liga;


# Classify these glyphs as 'ligatures'
# in the GDEF table,  and all other
# glyphs as 'baseglyphs'

gdef {

baseglyphs default
ligatures f_f_i f_f_l f_f f_i f_l f_j f_b f_h f_k;

} gdef;


I must be doing something wrong, but I can't figure out what it might be. Can somebody help? The old-style numbers work correctly, by the way.

[budgie]

Really silly question.

Am I supposed to name my ligature glyphs "f_f_i", etc.? My font has them named "ffi", etc. If I remove all the underscores from the liga feature lines, everything works.

Another really silly question. Is "by" a reserved name, such that I cannot name a glyph "by"? I could imagine all sorts of confusion otherwise.

I can't find anything in the user manual about naming of glyphs.

[Allan Murray]

f_f_i etc is the conventional naming for OpenType ligatures, but if you want to name your glyphs something different, then you need to adjust the feature files as you have done.

Note: fl and fi exist historically (before OpenType features existed) in unicode, which may cause confusion about appropriate naming.

Best to avoid using 'by' and 'from' as glyph names.