bug#57693: 29.0.50; Is there a more reliable version of `char-displayable-p'?

[Eli Zaretskii]

> From: Ihor Radchenko <yantar92@gmail.com>
> Cc: 57693@debbugs.gnu.org
> Date: Wed, 14 Sep 2022 09:52:59 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > So an efficient method of testing this for terminal would be:
> >
> >   . if terminal-coding-system is UTF-8, call internal-char-font to see
> 
> On my side, (terminal-coding-system) returns 'utf-8-unix
> However, I imagine that other utf-8 variants may be returned, say, on
> Windows.
> 
> Is there some standard way to know is a coding system is utf-8 or not?

Yes, use coding-system-base.