Generating alternate substitution features

Glyphs
1

How do I generate an alternate substitution feature automatically, say I want:

feature salt {
 sub a from [a.salt1 a.salt2 a.salt3];
} salt;

(it would be nice if it worked with any feature tag, but that is not a requirement for my case right now, any non-default feature tag will do).

2

That should work just like that (according to the FDK feature spec. I’ll try tomorrow.

3

Sorry, my question was not about the syntax, but about automatically generating such a feature.

4

To generate that automatically, we would need to establish a naming scheme. But as it is very rare, it might not be worth it.
You could write a script that generates the code.

5

I don’t think it is that rare, several OpenType features need alternate substitutions e.g. ssty feature for math fonts, and rand feature (which is supported by HarfBuzz and Affinity Publisher), so I think establishing a syntax for this would still be a good idea. I’d suggest some thing simple as xxxxNNNN where xxxx is the feature tag, and NNNN the alternate number, then glyph can be named salt01…salt55, ssty1…ssty2, rand001…rand999 etc.

6

I’ll have a look.

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