Re: Allowing point to be outside the window?

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: emacs-devel@gnu.org,  dick <dick.r.chiang@gmail.com>
> Date: Sun, 05 Dec 2021 08:46:52 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > But you could perhaps avoid a separate flag if you'd set
> > w->cursor.vpos to a negative value when the cursor is outside of the
> > window.
> 
> Actually, it now seems that cursor_visible_p is currently totally
> redundant: cursor.vpos is already -1 when the cursor is supposed to be
> invisible.
> 
> Can that value be relied on?

Depends what for and how you want to rely on it.  It basically says
that the cursor position inside the window is unknown.  The "normal"
redisplay must always calculate some reasonable coordinates and put
them there, otherwise the cursor will not be visible, which is a
display bug.  If that is enough for you, then yes, you can rely on it.