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

[Ihor Radchenko <yantar92@gmail.com>]

Eli Zaretskii <eliz@gnu.org> writes:

> Also, what exactly does the test above intend to test?  Are you
> interested in whether this character can be displayed at all,
> regardless of which font is to be used, or do you want it to be
> displayed with the default face's font?
>
> To answer your question: the most accurate way is to actually try
> displaying the character and see if that works.  Not sure if it helps
> you, though especially since that code is in a defcustom, AFAIU.

Makes sense. Trying to determine if a character can be displayed
a-priori in defcustom was just the "easy" approach.

It makes sense that we must try to insert the character first in order
to know if it can be displayed. At least, individual buffers may have
buffer-local face-remapping-alist that may completely change the
display.

However, it is not very clear for me how to determine programmatically if
given character is displayable in buffer.

-- 
Ihor Radchenko,
Org mode contributor,
Learn more about Org mode at https://orgmode.org/.
Support Org development at https://liberapay.com/org-mode,
or support my work at https://liberapay.com/yantar92