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

[Lars Ingebrigtsen]

Eli Zaretskii <eliz@gnu.org> writes:

>> It's the same problem than with fontification-functions.  We cannot know 
>> what all these hooks that are installed by major and minor modes will do, 
>> we cannot hope to fix them one by one, so it seems to me that with 
>> long_line_optimizations_p, which is an unusual case anyway, it makes sense 
>> to "punish" them all in the same way.
>
> It sounds...too drastic.  Lars, WDYT?

I agree with Gregory that it makes sense to disable (some) fontification
stuff in long-line buffers.  It much more important to be able to view
and edit these files than getting fontification details completely
correct.

Of course, it'd be better if everything just worked perfectly, but
that's very ambitious.