bug#57207: 29.0.50; Fontification is slow after e7b5912b23 (Improvements to long lines handling)

[Eli Zaretskii]

> From: Ihor Radchenko <yantar92@gmail.com>
> Cc: gregory@heytings.org,  57207@debbugs.gnu.org
> Date: Tue, 16 Aug 2022 17:39:22 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Does the patch below fix the issue?
> 
> Nope, unfortunately.

OK, thanks.  The change is correct nonetheless, so I installed it.

Gregory, perhaps we should restrict the search even further, as this
loop could take some tangible time with very large files.  How about
if we search from window-start point instead of BEGV, and limit the
search by, say, 10,000,000 newlines and 200,000,000 characters,
whichever happens first?  Is it really likely to have files with so
many short lines, followed by long lines?