Subject: bug#56682: Fix the long lines font locking related slowdowns

From: Eli Zaretskii <[email-masked]>
Date: Sat, 23 Jul 2022 20:49:39 +0300

> Cc: [email-masked], [email-masked], [email-masked],
>  [email-masked]
> Date: Sat, 23 Jul 2022 20:44:43 +0300
> From: Eli Zaretskii <[email-masked]>
> 
> > Font-lock Scroll-bar Composition Output
> > ------------------------------------------------------------
> > on	  on	     on		 GCs: 16 Elapsed time: 5.496764 seconds
> > on	  off	     on		 GCs: 1 Elapsed time: 5.362916 seconds
> > on	  off	     off	 GCs: 1 Elapsed time: 3.947306 seconds
> > 
> > That's with
> > 280b8c96cc origin/feature/long-lines-and-font-locking Improve display of columns on mode-lin
> 
> Thanks.  So the scroll-bar effect is largely gone, and font-lock is
> now just 25% slower than no-font-lock.  Which I think is reasonable,
> given that there's a face change every 10 to 20 characters?

Oops, I was confused: font-lock OFF is not in the table, so with it
we're still 4 to 5 times slower than without it.  It's
auto-composition mode that costs us 25% slowdown.