bug#74924: 29.3; Buffer showing manpage jumps back to beginning

[Ture Pålsson]

1. Run in a terminal window. Operating system seems not to matter; I can
reproduce on both macOS and Linux.

2. Set environment variable MANWIDTH to 80 .

3. Start Emacs ('emacs -nw -Q').

4. Do M-x man, enter the name of some manpage, and type RET.

5. Switch to the manpage window (C-x o), and scroll down by typing 'C-v'
a few times.

6. Switch back to the *scratch* window (C-x o again).

7. After about a second, the manpage window jumps back to the beginning
of the buffer.

My *guess* is that this is related to the changes in commit
7e387c9e5265b98dbb3b986f8ab8ac2217052831, but that may well be a red
herring.



In GNU Emacs 29.3 (build 1, aarch64-apple-darwin23.4.0, NS
 appkit-2487.50 Version 14.4.1 (Build 23E224)) of 2024-04-28 built on
 agaton
Repository revision: 8d7918ec1f42048ed994dfd0e4d582d8acaabd45
Repository branch: master
System Description:  macOS 15.1.1

Configured using:
 'configure --prefix=/Users/ture/Nobackup/emacsbuild --with-ns
 --without-gif CPPFLAGS=-I/Users/ture/Nobackup/emacsbuild/include
 LDFLAGS=-L/Users/ture/Nobackup/emacsbuild/lib'

Configured features:
ACL GMP GNUTLS JPEG LIBXML2 MODULES NOTIFY KQUEUE NS PDUMPER PNG SQLITE3
THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER ZLIB

Important settings:
  value of $LC_CTYPE: sv_SE.UTF-8
  value of $LC_MESSAGES: C
  value of $LANG: sv_SE.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Fundamental

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  show-paren-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  blink-cursor-mode: t
  buffer-read-only: t
  line-number-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  view-mode: t

Load-path shadows:
/Users/ture/Library/Emacs Lisp/python hides 
/Applications/Emacs.app/Contents/Resources/lisp/progmodes/python

Features:
(shadow sort mail-extr emacsbug message yank-media puny dired
dired-loaddefs rfc822 mml mml-sec epa derived epg rfc6068 epg-config
gnus-util text-property-search time-date mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils view term/screen
term/xterm xterm ture-theme ansi-color finder-inf package browse-url url
url-proxy url-privacy url-expand url-methods url-history url-cookie
generate-lisp-file url-domsuf url-util mailcap url-handlers url-parse
auth-source cl-seq eieio eieio-core cl-macs password-cache json subr-x
map byte-opt gv bytecomp byte-compile url-vars cl-loaddefs cl-lib rmc
iso-transl tooltip cconv eldoc paren electric uniquify ediff-hook
vc-hooks lisp-float-type elisp-mode mwheel term/ns-win ns-win
ucs-normalize mule-util term/common-win tool-bar dnd fontset image
regexp-opt fringe tabulated-list replace newcomment text-mode lisp-mode
prog-mode register page tab-bar menu-bar rfn-eshadow isearch easymenu
timer select scroll-bar mouse jit-lock font-lock syntax font-core
term/tty-colors frame minibuffer nadvice seq simple cl-generic
indonesian philippine cham georgian utf-8-lang misc-lang vietnamese
tibetan thai tai-viet lao korean japanese eucjp-ms cp51932 hebrew greek
romanian slovak czech european ethiopic indian cyrillic chinese
composite emoji-zwj charscript charprop case-table epa-hook
jka-cmpr-hook help abbrev obarray oclosure cl-preloaded button loaddefs
theme-loaddefs faces cus-face macroexp files window text-properties
overlay sha1 md5 base64 format env code-pages mule custom widget keymap
hashtable-print-readable backquote threads kqueue cocoa ns multi-tty
make-network-process emacs)

Memory information:
((conses 16 81755 10005)
 (symbols 48 8456 0)
 (strings 32 27783 2349)
 (string-bytes 1 757038)
 (vectors 16 19632)
 (vector-slots 8 929234 167765)
 (floats 8 31 543)
 (intervals 56 292 0)
 (buffers 984 12))