bug#57669: 29.0.50; C-n, C-p off under long lines

[Eli Zaretskii]

> Date: Fri, 09 Sep 2022 16:06:57 +0000
> From: Gregory Heytings <gregory@heytings.org>
> cc: dick <dick.r.chiang@gmail.com>, 57669@debbugs.gnu.org
> 
> > I'm aware of your "solution", and it is unacceptable.
> 
> I'm not, I asked him a few pointers, and he replied with the hash of a 
> commit which disables what exists on master.

The code is there, you can read it.  Don't just rely on my
conclusions, because I may be wrong.

> Perhaps there's something useful in his solution, even if it is
> unacceptable?  If you already know what it is, can you perhaps
> describe it in a few words?

In a nutshell, his changes disable too many features of the GUI
display (the ones that make the Emacs display slow with long lines),
and they disable those features _always_, not just when the lines are
long.

And that is _after_ you factor out changes that are plain wrong,
because he simply didn't understand what the code does well enough.