bug#14582: 24.3.50.1; Strange overlay behavior, when window-start is inside an overlay.

[Eli Zaretskii]

> From: Michael Heerdegen <michael_heerdegen@web.de>
> Cc: larsi@gnus.org,  esabof@gmail.com,  14582@debbugs.gnu.org
> Date: Tue, 08 Feb 2022 05:05:08 +0100
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > But what does this have to do with this bug report and the new
> > make-window-start-visible feature?
> 
> It only happens when the new feature is turned on.  Sorry that I failed
> to make that clear.  Never saw this problem before.  Issue disappears
> when turning the new feature off.

Why would you turn on make-window-start-visible in Info buffers?

> But I don't see the problem in -Q when I enable
> make-window-start-visible.

Neither do I, so there's something else at work here.

> I asked for your ideas because finding a recipe is a bit harder this
> time.  Just evaluating my big "set all important options" block in emacs
> -Q is not enough.  I guess I will need 10 or 15 mins, so don't waste
> your time when a related setting is not obvious.  It doesn't seem to be
> just a simple scroll-* option.  I guess it's not scrolling related at
> all but simply caused by the new feature.

The new feature overrides the decision about window-start made by
redisplay, and that is very closely related to scrolling, because
scrolling in Emacs works by basically setting the window-start point
and letting redisplay do the rest.