Re: Scrolling commands and skipping redisplay, was: Re: emacs rendering comparisson between emacs23 and emacs26.3

[Dmitry Gutov]

On 10.04.2020 16:34, Eli Zaretskii wrote:
> It doesn't flicker here.  Maybe the double-buffering is the reason?

Double-buffering decreases the number of display updates, so it hardly 
can be the cause of this.

As we've discussed with Stefan, the implementation is likely the reason.

> With -Og, if you set jit-lock-defer-time to 0.5, doesn't it scroll
> much faster? does it flicker then?

It doesn't scroll much faster than with the value of 0 (that already 
scrolls fast enough).

It doesn't flicker while scrolling because it simply shows unfontified 
screenfuls of code. Which is unacceptable for default behavior. And I'd 
hesitate to recommend it to anyone even to deal with performance problems.

It *does* flicker afterwards (e.g. 0.5 sec after I depress C-v), because 
that's what deferred jit-lock does: it applies syntax highlighting with 
a delay. So I type, wait 0.5sec, and syntax highlighting arrives. It's a 
less-aggravating kind of flicker because of its laid-back pace, but I 
still wouldn't call it acceptable user experience.