bug#56393: Actually fix the long lines display bug

[Eli Zaretskii]

> Date: Sat, 09 Jul 2022 12:07:55 +0000
> From: Gregory Heytings <gregory@heytings.org>
> cc: gerd.moellmann@gmail.com, larsi@gnus.org, 56393@debbugs.gnu.org
> 
> 
> >
> > That's very strange, since AFAIK moving in a non-fontified buffer 
> > involves both fontifications and display of the fontified text, whereas 
> > moving through a fontified buffer involves only the latter. FWIW, I've 
> > _never_ seen movement through fontified buffer being slower than in a 
> > non-fontified one.
> >
> 
> Try the dictionary.json or the long-line.xml file with and without 
> font-lock-mode.  Also try
> 
> emacs -Q
> C-x C-f dictionary.json RET
> y
> C-s aan zich RET
> 
> and
> 
> emacs -Q
> C-x C-f dictionary.json RET
> y
> M-x font-lock-mode
> C-s aan zich RET
> 
> The first takes several seconds, the second is almost instantaneous.

Ah, I misunderstood what you were saying.

But you originally talked about C-n and vertical-motion, not about
C-s.