I’m currently working on the first font in Robofont … I created some new glyphs, A–Z and 0–9 for stylistic sets 01, 02, and 03 …

I’d like to ask, how can I assign those glyphs a unicode codepoint?

And would e.g. A.ss01 get the same unicode codepoint as A? (I think so, but I’m not completely sure …)

Thank you so much!

It’s not allowed to provide two glyphs with the same unicode value. Thinking from a typesetting point of view: which one should it take?

I would recommend you to write an OpenType feature to switch the A to the alternate A.ss01 in InDesign:

feature ss01 {
    sub A by A.ss01;
    # ...
} ss01;

thank you for your answer!

Why would an alternate version get a unicode value?
It’s not allowed to provide two glyphs with the same unicode value. Thinking from a typesetting point of view: which one should it take?

I see, so … there’s no problem here, but it’s actually right that the alternates named e.g. A.alt or A.ss01 don’t have the same unicode value as A itself … thank you for clarifying this.

I would recommend you to write an OpenType feature to switch the A to the alternate A.ss01 in InDesign:

I see! So it seems I’ll try to read the Robofont page on features and the documentation from Adobe and then I can hopefully figure out what to write in that feature file as now it’s completely empty.

I mean, maybe this feature files needs to have lines like the following:

 # Script and language coverage
 languagesystem DFLT dflt;
 languagesystem latn dflt;

And afterwards I could manually add what you proposed for A–Z and 0–9 in ss01, ss02, and ss03.

feature ss01 {
    sub A by A.ss01;
    # ...
} ss01;

I saw something like A.alt in some free and open source .ufo files and was wondering what it is, i.e. why would I write .alt instead of some styleset like .ss01 …

EDIT:

I just discovered an article about opentype features on i love typography dot com which lists features like aalt “All alternates“, calt “Contextual alternates“, salt “Stylistic alternates”, et cetera (which I already know from CSS).

So I think for another stylistic version of the figures 0–9, salt would be a kinda semantically correct feature name.