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

[dick]

> Commercial Emacs performs much worse

I dunno.  As of 103caad, Commercial runs through the 100-line test in
3s, about the same as GNU with find-file-literally and non-nil
long-lines-threshold.

I never said your method was inspired by mine, merely your words
in describing the long lines situation, and your motivation to even
tackle the problem.  I would have never thought to bring to bear a
seemingly unrelated thing like narrowing.  I was impressed, although the
impedance mismatch of your creative solution is becoming more obvious.

You're right, though.  Boy, am I am hopping mad.