GNU bug report logs - #56682
Fix the long lines font locking related slowdowns

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Message #275 received at 56682 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Dmitry Gutov <dgutov <at> yandex.ru>
Cc: gerd.moellmann <at> gmail.com, 56682 <at> debbugs.gnu.org, gregory <at> heytings.org,
 monnier <at> iro.umontreal.ca
Subject: Re: bug#56682: Fix the long lines font locking related slowdowns
Date: Thu, 28 Jul 2022 09:21:46 +0300

> Date: Thu, 28 Jul 2022 00:38:09 +0300
> Cc: gerd.moellmann <at> gmail.com, 56682 <at> debbugs.gnu.org,
>  Eli Zaretskii <eliz <at> gnu.org>, monnier <at> iro.umontreal.ca
> From: Dmitry Gutov <dgutov <at> yandex.ru>
> 
> > Yes, occasional mis-fontification is expected.  It's a compromise 
> > between "no fontification" and "slow fontification".
> 
> I wonder now if the majority of the slowdown was caused by the 
> redisplay, whereas font-lock (which only has to run once per screenful) 
> was actually "fast enough".

To establish that, you can run font-lock-fontify-buffer, wait until it
finishes, and then try moving around and comparing that with a buffer
in which font-lock was turned off.  (Do this on master, of course,
where the changes we are discussing are not yet installed.)

In general, even after a full fontification, you should see at least
some slowdown due to the faces.  How much slowdown, quantitatively, I
don't know, but perhaps Gregory measured that as part of his work.

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