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: Sat, 04 Dec 2021 21:13:40 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > In general, it's hard to provide useful feedback without understanding
> > the main ideas of the changes.  And you didn't add any comments to
> > help in that.  So I'm left to wonder whether some changes I don't
> > think I understand are just my misunderstanding of your ideas, or your
> > misunderstanding of the code.
> 
> I will work on that, sorry.

Btw, one issue that I couldn't figure out from reading the patch is
how do you intend to distinguish between point going out of the
viewport by an explicit user command (which AFAIU is what we want to
support in this new mode), and point going out of the viewport for
some other reason, for example text insertion before point?
Specifically, the bother is this: if we just disable/bypass all the
places where Emacs brings point back into the window, we could find
point outside of the window without the user meaning that to happen,
and the disabled/bypassed code will then leave point invisible.

So I think a single variable set by the user once and globally is not
enough to control the changes in the display code to support this
mode.  We need some variable that is per window and is set dynamically
depending on what caused point to go out of the viewport.  This will
quite naturally lead to defining the command that we will allow to
create such a situation, because only those commands will be able to
set that dynamic variable, and only for a window where those commands
were invoked.  (I guess some of the scrolling commands will be in that
group.)