Re: emacs rendering comparisson between emacs23 and emacs26.3

[Stefan Monnier]

> apparently takes 30 to 35 calls to get into those ~10 second freezes.
[...]
> I cannot nearly simulate the problem using a simple loop that steadily
> invokes say (forward-line 50) followed by a (sit-for 0).  50 such
> invocations take 16.7 seconds here, 22.7 with (forward-line -50).

16s in one case a "10 seconds freeze": it sounds to me like you *do*
reproduce the problem.
The only difference is that with actual keyboard input pending the
redisplay is partly prevented which is what you perceive as "freeze",
but the real problem is the time it takes.

> But what's "fast enough"? Fontification that is faster than the signal rate
> of the keyboard?

Yes.  Of course, that depends not only on Emacs's code and the
optimization level, but also on your CPU and your keyboard
repetition setting.


        Stefan