Re: Allowing point to be outside the window?

[Eli Zaretskii <eliz@gnu.org>]

> From: Po Lu <luangruo@yahoo.com>
> Cc: emacs-devel@gnu.org
> Date: Mon, 07 Feb 2022 21:57:50 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> >> And I question the validity of the combination scroll-move-point = nil
> >> >> with keep-point-visible = t.  The problem with your implementation is
> >> >> that scroll-move-point = nil disables scrolling in redisplay_window,
> >> >> but scrolling there is used not necessarily as result of scrolling
> >> >> commands, but also when redisplay_window decides that the optimal
> >> >> method of updating a window is to scroll its previous contents.  Thus,
> >> >> disabling scrolling on that level will cause confusing results,
> >> >> because users will expect that to affect only scrolling commands: they
> >> >> are unaware that redisplay sometimes scrolls the window for other
> >> >> reasons.
> 
> > I didn't say redisplay calls the scrolling commands: you did.
> >
> > The truth is that redisplay doesn't call any scrolling commands.
> 
> `scroll-move-point' doesn't affect redisplay; it only affects the
> scrolling commands in window.c.

It does affect redisplay: by not setting the force_start flag of the
window.

> I thought what you wrote was a typo, and that you meant to say "disables
> scrolling in window.c" or something else similar.

No, the problematic word was "scrolling": I meant the large block in
redisplay_window conditioned by w->force_start being non-zero.  That
includes the code under try_to_scroll.