bug#27932: 26.0.50; Feature request: prevent scroll commands from changing the buffer location of point

[Eli Zaretskii <eliz@gnu.org>]

> From: Richard Stallman <rms@gnu.org>
> CC: dmoncayo@gmail.com, 27932@debbugs.gnu.org
> Date: Fri, 04 Aug 2017 17:36:07 -0400
> 
>   > It would require a complete rewrite of most of the display engine
>   > code.  The Emacs display engine is based on the principle that point
>   > should always be visible, so whenever it becomes invisible, Emacs
>   > scrolls the window to make it visible again.
> 
> I don't think the change would be terribly hard.  One would have to
> find the places that insist on putting point on the screen, but I
> think the changes required in each of those places would not be big.

The number of such places got a lot larger than it was when you were
more actively hacking Emacs, because over the years some users (Dani
included) requested more and more accuracy in that direction.

As for whether the changes in those places are hard, depends on how
well the person who'll do that understands what the code they are
looking at is doing, and why.  The answer might not always be obvious.

And then there are higher-level issues, like what does this mode mean
when scroll-conservatively is in effect.

> If someone wants to try it, I encourage per to try it.

Me too.  In fact, I'd encourage even smaller changes related to the
display code, so that we have more people who can make changes there
than we do now.