bug#72830: Big rectangular selections are slow

[Juri Linkov <juri@linkov.net>]

>> 27 aug. 2024 kl. 15.48 skrev Eli Zaretskii <eliz@gnu.org>:
>>
>> > Does turning off auto-composition-mode help in any way?
>>
>> I don't think so. Were you able to reproduce the problem?
>
> I didn't have time to try, sorry.  Too much stuff on my plate, and
> still only 24 hours a day, even with Emacs 30...

For Emacs 30 it's time to increase the default value of hours-per-day to 30.

>> 27 aug. 2024 kl. 16.04 skrev Stefan Monnier <monnier@iro.umontreal.ca>:
>>
>> More promising to me would be to try and skip any part of the buffer
>> that's not displayed.
>
> Yes, I see no reason for having the highlight overlay on something that can't be seen.
>
> But how do we know what the viewport will be in
> `rectangle--highlight-for-redisplay`? Since it is redisplay that determines
> window-start and window-end, and it hasn't run yet, this puts us in some
> kind of chicken-egg situation. Maybe it has to be done inside redisplay.

I'm sure it should be possible to use `pre-redisplay-functions'
that by default updates region highlighting, and I was able to use it
to make region highlighting window-local even when the same buffer
is displayed in separate windows.