bug#46508: 27.1; Emacs doesn't like ⿰

[Eli Zaretskii]

> Date: Tue, 16 Feb 2021 10:28:32 +0100 (CET)
> From: Werner LEMBERG <wl@gnu.org>
> Cc: schwab@linux-m68k.org, benkasminbullock@gmail.com, 46508@debbugs.gnu.org
> 
> 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.

Terminal emulators typically try a much smaller set of fonts than
Emacs does, because they generally use only fixed-pitch fonts, AFAIK.

> Is there something that could be done on the Emacs side to improve its
> behaviour?

Customizing your fontset would be one way.

> For example, putting the font retrieving process into a separate
> thread, providing a dummy glyph until the real one is available?

That's quite a project: the font search code accesses Lisp data
structures, so running that asynchronously would need some kind of
locking or working on copies of those Lisp data structures or
somesuch.  And then we'd need some mechanism to trigger redisplay once
the search is over.

> What does the terminal do to be so much faster?

That's an excellent question, to which I'd love to know the answer.