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

[Dmitry Gutov]

On 10.08.2022 15:04, Eli Zaretskii wrote:
> > Date: Wed, 10 Aug 2022 14:54:51 +0300
> > Cc:56682@debbugs.gnu.org, Eli Zaretskii<eliz@gnu.org>,
> >   monnier@iro.umontreal.ca
> > From: Dmitry Gutov<dgutov@yandex.ru>
> >
> > On 10.08.2022 13:55, Stephen Berman wrote:
> > > Indeed, setting bidi-inhibit-bpa to t eliminates the delay.  Thanks.
> > Same here.
> >
> > And the "faster computer" didn't help, apparently.
> >
> > After flooring 'C-n', I even had to 'C-g' out of it for Emacs to regain
> > responsiveness, because waiting for a while didn't help.
> That's strange, because on my "slower" computer I didn't see anything
> like that.

I think that just confirms what I said: the test "floor the button and 
see of UI freezes" is not a good one because it doesn't work against any 
objective numbers. It compares the speed of command execution with the 
speed of redisplay, and there is no backpressure mechanism.

If the "faster computer" executes the commands faster as well, it can 
likewise enter the unresponsive state.