Thank you for your reply.

What kind of fallback?


I want to detect if char is visible and use a different one. E. g. bulb can
be replaced with "!".


> IOW, what did you intend to do if you find out
> that the font configured by the user does NOT have a glyph for the
> character in question?
>

Yes.


> I'm asking because some fallbacks don't need to know whether a
> particular font can display a particular character.  But I'm not sure
> those fallbacks are appropriate for your use case.
>
> > I tried to use char-displayable-p but it seems like it is not
> > what I am looking for.
>
> I believe you want font-get-glyphs.
>

I will try that out. I am not sure what FONT-OBJECT parameter stands for?

Thanks,
Ivan