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

[Eli Zaretskii]

> From: Stefan Kangas <stefankangas@gmail.com>
> Date: Fri, 9 Sep 2022 18:25:27 -0400
> Cc: 57693@debbugs.gnu.org
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > I'd need to know more details.  Why did this test fail for that user?
> 
> You can find the details here:
> https://lists.gnu.org/r/emacs-orgmode/2022-07/msg00402.html

I'm probably missing something, because I didn't see there an
explanation of the problem I was looking for.

The problem which AFAIU Ihor raised was that char-displayable-p
returns non-nil, when the character actually cannot be displayed.
This is what I'm asking: how come char-displayable-p thought it could
find a font for the character, when Emacs failed to find the font when
it was time to actually display that character?

Ihor says that the reason could be some buffer-specific settings that
char-displayable-p didn't take into consideration.  If that's the
reason, could someone tell what those settings were in this case?