bug#20499: [PROPOSED PATCH] C-x 8 shorthands for curved quotes, Euro, etc.

[Eli Zaretskii]

> Date: Fri, 8 May 2015 13:18:40 -0700 (PDT)
> From: Drew Adams <drew.adams@oracle.com>
> Cc: 20499@debbugs.gnu.org
> 
> > > We could set up a way to test whether a code point can be
> > > displayed, and skip scripts that can't be displayed.
> > 
> > Alas, we don't know which cannot be displayed until we've tried and
> > failed.
> 
> Where is this try-and-fail done?  Is it only in C code, or is
> there some Lisp function (predicate) that you can call to tell
> you whether a given char can be displayed in a given (e.g. the
> current) font.

These two are not alternatives, they can (and do) live together.

The search for a suitable font is mostly in C, but we do have a
capability to test from Lisp whether a given character can be
displayed: 'char-displayable-p'.  If you are interested in a specific
font, you can use 'font-get-glyphs' for a similar info.