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

[Dmitry Gutov]

On 09.04.2020 16:19, Stefan Monnier wrote:
> BTW, you can also set `jit-lock-defer-time` to 0 in which case jit-lock
> is deferred iff there's input pending.
> [ This refinement of `jit-lock-defer-time` was introduced last time
>    this kind of discussion took place, which is also the time
>    `fast-but-imprecise-scrolling` was introduced.  ]

Thanks. I tried it (and mentioned in the parent thread), but it seems 
like in addition to the downsides of f-b-i-s (imprecise scrolling, which 
apparently makes it a bad candidate for default behavior) it adds some 
extra flickering from time to time (I figured because some redisplays 
occurred before the idle timer had the chance to run). It's not as 
obvious in an 'emacs -Q' session, but with my custom config it's more 
apparent. And that flickering occurs the most while I'm flooring C-v.

Is it possible that the conditions for skipping redisplay might return 
false while input-pending-p returns t? Then redisplay will occur, but if 
that coincides with an unfontified screenful, the screen will be 
rendered unfontified? That doesn't explain the additional frames where 
that highlighting is added, however.