Re: Make scroll-{up, down} move point to {start, end} of newly visible text

[Eli Zaretskii <eliz@gnu.org>]

> From: Spencer Baugh <sbaugh@janestreet.com>
> Date: Wed, 16 Aug 2023 13:55:42 -0400
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> (defun my-scroll-up-command (&optional arg)
> >>   (interactive "^P")
> >>   (move-to-window-line -1)
> >>   (scroll-up-command arg))
> >> 
> >> (defun my-scroll-down-command (&optional arg)
> >>   (interactive "^P")
> >>   (move-to-window-line 0)
> >>   (scroll-down-command arg))
> >> 
> >> except of course this implementation moves point even if it's not
> >> necessary.
> >> 
> >> Does this seem like a reasonable feature to add to the scrolling code?
> >
> > I don't understand what you have in mind.  The above commands seem to
> > do what you want only when ARG is 1.  Or what did I miss?
> 
> They're actually wrong when ARG is 1, because they move point without
> needing to.  They mostly only work when ARG is nil.

That's what I meant: only 1 widow-full scroll.

> See the prose description of what I want, the commands are close to but
> not exactly right because they move point unnecessarily:
> 
> >> When point is off-screen after scroll-up, we should first try to move
> >> point to "window-end before we scrolled", and only if that position is
> >> also off-screen should we move point to window-start.  (Currently we
> >> unconditionally move point to window-start)
> 
> > For scrolling just one window-full, setting next-screen-context-lines
> > to 1 should do what you want.  For scrolling more than that, I don't
> > understand how to generalize what you want.
> 
> The prose description I gave generalizes just fine, doesn't it?  The
> prose description is completely invariant to how much scrolling is done.

Either setting next-screen-context-lines to 1 should do what you want,
or I still don't understand what you want when scrolling by more than
one window-full.