Weird font problem

[Joost Kremers]

Hi list,

Apologies for the non-descript subject line, but I really don't know how to be
more precise... 😧

I'm running into a weird problem with displaying certain Unicode symbols. The
relevant symbols are not displayed in a normal buffer, because Emacs cannot find
a font set that has a glyph for them. However, when I try to insert such a
character with 'C-x 8 RET', with vertico installed, I see the following (trying
to insert DOCUMENT 0x01F5CE):

The DOCUMENT character is replaced with the missing glyph box, but the other
characters *are* displayed. When I move the highlight down (M-n), the following
happens:

Suddenly, DOCUMENT *is* displayed, and the character that is highlighted is not.
Moving the highlight further down or back up gives the same effect for the other
characters.

Things get even weirder, though: After taking a screen shot, suddenly *all*
characters are gone:

This happens on two different computers, both running the same OS (Arch Linux;
GNOME 46 on Wayland) and Emacs version (GNU Emacs 29.3 (build 1,
x86_64-pc-linux-gnu, GTK+ Version 3.24.41, cairo version 1.18.0)).

The fact that the symbols are displayed in the completion list suggests to me
that Emacs seems to have a way to find glyphs for them. If that is correct, then
why doesn't it find them when the characters are in a "normal" buffer?

Or is there something else that makes those characters appear, outside of Emacs'
control? The fact that taking a screen shot has such an effect seems to indicate
this...

And I'm also wondering what I can do to make Emacs find a glyph for these
characters. Other applications, including GNOME Terminal, gedit and LibreOffice
have to trouble displaying them.

Any and all hints are appreciated.

Joost



-- 
Joost Kremers
Life has its moments