bug#46508: 27.1; Emacs doesn't like ⿰

[Werner LEMBERG]

> Ben> This caused the problem to occur again and emacs -Q stalled
> Ben> completely. I then restarted emacs with emacs -Q without
> Ben> opening the problem file (which contains a single ⿰). In the
> Ben> new Emacs window I copy-pasted the above code and ran
> Ben> 'eval-buffer' then I used C-x C-f to load the file containing
> Ben> the ⿰ single character. I then started typing this email, and
> Ben> it is still unable to load the file containing the ⿰ even as I
> Ben> am typing now. It finally loaded after several minutes, but the
> Ben> ⿰ character is not displayed, instead there is a box with 2FF0
> Ben> in it.
>
> I have no problems displaying that codepoint, because I have a
> scalable font installed that can display the character, [...]

Exactly.  However, this is not always the case, and the freeze of
Emacs is very, very annoying.  Other applications like my KDE terminal
is stalled only for approx. a second in similar situations.

Is there something that could be done on the Emacs side to improve its
behaviour?  For example, putting the font retrieving process into a
separate thread, providing a dummy glyph until the real one is
available?  Or maybe something else?  What does the terminal do to be
so much faster?


    Werner