Family-dependent font matching fallbacks?

[Omikhleia]

Unless I misunderstood the docs and my own tests, it seems \font:add-fallback adds the fallback font globally. If there are several fallback fonts that could provide missing characters in the current font at a point, the order in which one of those fallback is picked is not obvious.

I am looking at something similar to CSS font-family with its alternative list of fonts -- So that I could, for instance, set appropriate fallbacks for my main document font (say, a serif font matching it nicely), but other fallbacks for my title font (say, a sans-serif font), yet other appropriate fallback for my example fonts (say, another serif font, but where another fallback could look nicer). There could still be "general" fallback defaults in the end, but at least the picked font would depend on my choices if available.

Is it something that is doable with SILE?

[alerque]

Doable yes, currently implemented no.

I would like to add some sort of "family" group handling, not specifically for the same way you may want it but to make classes easier to customize. I already did this for CaSILE—styling a book involves setting a serif font and a sans font and a mono font and a display font (and for some designs, and decorative font, etc. It would be a lot easier if there was more upstream logic to handle these rather than passing everything though options inherited between commands.

Tying a fallback stack to current font settings makes a lot of sense to me.

[alerque]

Doable yes, currently implemented no.

I would like to add some sort of "family" group handling, not specifically for the same way you may want it but to make classes easier to customize. I already did this for CaSILE—styling a book involves setting a serif font and a sans font and a mono font and a display font (and for some designs, and decorative font, etc. It would be a lot easier if there was more upstream logic to handle these rather than passing everything though options inherited between commands.

Tying a fallback stack to current font settings makes a lot of sense to me.