Re: emacs rendering comparisson between emacs23 and emacs26.3

[Stefan Monnier]

> What's the difference between redisplay being slow and it being unable to
> "keep up"? I don't understand, sorry.

If there's already input waiting (because the next event already
arrived) at the start of redisplay, then redisplay is short-circuited.

Typically, in an auto-repeat circumstance, this will either not happen
or happen on a whole batch of repetition.  So we say "can't keep up"
because processing of one command (including redisplay) takes more time
than the interval until the next command.

> And in this case, IIUC, jit-lock is part of redisplay.

Yes, it often is when scrolling.


        Stefan