bug#32159: 26.1; inhibit-compacting-font-caches does not fix all fonts lagging issue

[Eli Zaretskii]

> From: Moses <moses.mason@gmail.com>
> Date: Sun, 15 Jul 2018 05:50:26 +0000
> Cc: 32159@debbugs.gnu.org
> 
> You are right. I got 5906 installed fonts returned from (length
> (x-list-fonts "*")). However, this still a problem, which is really
> annoying when editing files that contain more than one language.

Do some of the characters in HELLO display as boxes with hex code
inside them, and if so, do you see slow-down when Emacs is about to
display those characters?  If the answer to both question is YES, I
can suggest a customization to try that might help you avoid the
slowdown (assuming you don't need to be able to display characters
from those scripts), but please tell what characters are involved in
this.

> Other editor does not have the similar issue.

AFAIK, no other editor supports such a large variety of fonts.

> I am not an expert, but as far
> as I know, the font fallback link is already stored in the register
> under key HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows
> NT\CurrentVersion\FontLink\SystemLink, why Emacs still needs to search
> fonts multiple times?

I don't think that Registry setting is relevant to the issue at hand.
Emacs looks for fonts based on its internal database of features
required by each script.