bug#9607: incorrect behavior with "auto-hscroll-mode nil" in ncurses/vt220 text operation; wrong in 23 but ok in 22.1

[Glenn Morris]

Present in 23.2 to 24.0.90 inclusive. Recipe:

emacs -Q --eval '(setq auto-hscroll-mode nil)'

Evaluate:
(dotimes (j 5)
  (insert "\n")
  (dotimes (i 10)
    (insert "0123456890 ")))

Put point at start of first line of digits.
M-x scroll-left RET y
;; Window now scrolled to right-hand end of lines
Down arrow  ; first time is ok
Down arrow
  -> second time window scrolls back to left-hand end of line


(setq line-move-visual nil)

avoids the problem.

I guess it's related to the 2009-07 changes to line-move-visual for hscroll.