bug#26333: 26.0.50; Hang when displaying some special characters for the first time

[Steven Allen]

So, I could have sworn I tested this with emacs -Q when I first found
the bug (I've been sitting on it for a while) but I guess I didn't. I
apologize.

It only reproduces for certain fonts.

Known Bad: Source Code Pro, Office Code Pro, Fira Mono
Known Good: Symbola, DejaVu Sans Mono (the default on my system)

So, to reproduce, evaluate the following before pasting the special
character.

  (set-face-attribute 'default nil :font "Source Code Pro-10")

Eli Zaretskii <eliz@gnu.org> writes:
> That's normal:

Hardly. 15 seconds is a *long* time for a computer and every other
application displays the character in question instantly. Not even
regenerating my entire font cache (fc-cache) takes that long.

> If you install the Symbola font, I think the search will
> be much faster.

I do have Symbola installed and the character does display correctly
eventually.