fina feature

Read,

first of all, thanks for your extensive explanation and complete response to my doubt. I think that your question at the beginning of your answer is not necessary because you gave me the solution right afterwards.

Jordi

It would be helpful if you could say what " does not work" means in practice

I hope the following comments help solve the problem.

As feature file syntax, your syntax is correct, and will build a properly formed lookup.

One reason that it may not work is how the feature is applied. I see that the
http://partners.adobe.com/asn/tech/type/opentype/appendices/features_fj.jsp#fina
says of 'fina' that;
Recommended implementation: The fina table maps default alphabetic forms to corresponding ending forms (GSUB lookup type 1).
meaning that it does only a one to one substitution.

There are two ways to get there.

1) do a ligature substitution first

feature liga {
sub n t by n_t;
}

feature fina {
sub n_t by n_t.end;
}

However, this requires both features to be on. Since this looks like a an alternate form that it is not required, and requires context, I think it would be reasonable to put in the clig feature, and simulate end-end-of-word matching yourself. This is what we do for end-of-word ligatures in script fonts. It is something of a hack, but in the absence of "end of word" marks, it is the best that can be done.. To do this, you first use an 'ignore' rule to match all non-end of word conditions, and and then put your substitution rules after that.

@LETTERS = [ < all letters in the font that could be part of a word>];
feature clig {
lookup BEGIN_WORD_LIGS {
ignore @LETTERS @LETTERS'; # will match any word glyph preceeded by another word glyph.
sub c t by c_t.begin; # you know that there is no word glyph before the 'ct' sequence.
};
lookup END_WORD_LIGS {
ignore @LETTERS' @LETTERS; # will match any word glyph followed by another word glyph.
sub o f f by o_f_f.end; # you know that there is no word glyph after the 'off' sequence.
};
} clig;

Since each lookup is applied to the entire text string from beginning to end in turn, an 'ignore' rule shelters only the rules that follow it in the same lookup.