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

[Eli Zaretskii]

> From: Stefan Monnier <address@hidden>
> Cc: Dmitry Gutov <address@hidden>,  address@hidden,  address@hidden,
>   address@hidden,  address@hidden,  address@hidden
> Date: Thu, 16 Apr 2020 16:20:56 -0400
> 
> >> - Implementation-wise, not all commands simulate redisplay during their 
> >>   operation.
> > I think you will find that many more do than you seem to assume.  Even
> > just redisplaying a window does this in many cases (to find the proper
> > place for window-start position).  C-n and C-p do as well.
> 
> char-based, word-based, and sexp-based motion doesn't.  But line and
> motion that depends on "visual size" indeed typically does.

Also some functions that have nothing to do with movement, like
posn-at-point.  In a nutshell, any function that needs to consider
layout, and any command that uses such functions.

> > And when scroll-conservatively is in effect, almost every command that
> > moves point does.
> 
> Really?  I thought `scroll-conservatively` only affects the redisplay
> code and not the execution of "normal" commands (i.e. commands which
> don't themselves rely on simulating redisplay).

Like I said: redisplay itself calls those functions internally in many
situations, and scroll-conservatively > 100 makes it use that much
more.  When I said above "almost every command", I meant redisplay
triggered after commands that move point.