bug#24918: 25.1; Fonts can make Emacs grind to a halt

[Eli Zaretskii]

> Date: Tue, 29 Nov 2016 23:17:51 +0000
> From: Alan Third <alan@idiocy.org>
> Cc: Eli Zaretskii <eliz@gnu.org>, 24918@debbugs.gnu.org
> 
> I experience these slow‐downs too on my work (Windows 10) PC.
> 
> I found that I could reduce the delays by defining fallback
> fonts explicitly using:
> 
>     (set-face-attribute 'default nil :font "Droid Sans Mono")
>     (set-fontset-font nil 'unicode "DejaVu Sans" nil 'append)
>     (set-fontset-font nil 'unicode "Courier New" nil 'append)
>     (set-fontset-font nil 'unicode "Symbola" nil 'append)
> 
> but it doesn’t get rid of them completely.

Your font-spec argument in the above doesn't specify the registry.
See the definitions in fontset.el (search for "Symbola") for a better
way, which I think should avoid the delays.