bug#69534: Scrolling up causes all text to shift drastically when cursor hits bottom of viewable area.

[Arkdae via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

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Start 'emacs -Q'. Open a long document which is longer than can fit in
the window all at once. C-x 2 to split into two windows. Drag with the
mouse on the information bar with button one to shrink the bottom
window a bit. Then grab the scroll bar in the top window and drag up.

The cursor reaches the bottom. Then I slowly scroll one more pixel up
and all of the text contents are repositioned with the cursor at the
middle. The next pixel scrolled up keeps the cursor in the middle and
corrects the text to where it should have been.

Scrolling at normal speed causes flickering due to this, and when I am
trying to follow my place to see where I need to get to, it is hard due
to this shifting every half-page. Scrolling down does not shift the
text in this way, and the cursor correctly moves to stay within the
viewable area.

In GNU Emacs 29.2 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.40,
cairo version 1.18.0)
Windowing system distributor 'The X.Org Foundation', version
11.0.12101011
System Description: Arch Linux

Configured using:
 'configure --sysconfdir=/etc --prefix=/usr --libexecdir=/usr/lib
 --with-tree-sitter --localstatedir=/var --with-cairo
 --disable-build-details --with-harfbuzz --with-libsystemd
 --with-modules --with-x-toolkit=gtk3 'CFLAGS=-march=x86-64
 -mtune=generic -O2 -pipe -fno-plt -fexceptions -Wp,-D_FORTIFY_SOURCE=2
 -Wformat -Werror=format-security -fstack-clash-protection
 -fcf-protection -g
 -ffile-prefix-map=/build/emacs/src=/usr/src/debug/emacs -flto=auto'
 'LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now -
flto=auto''

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBOTF LIBSYSTEMD LIBXML2 M17N_FLT MODULES NOTIFY INOTIFY
PDUMPER PNG RSVG SECCOMP SOUND SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS
TREE_SITTER WEBP X11 XDBE XIM XINPUT2 XPM GTK3 ZLIB

Important settings:
  value of $LANG: en_US
  locale-coding-system: iso-latin-1-unix

Major mode: Fundamental

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

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message yank-media dired dired-loaddefs
rfc822 mml mml-sec epa derived epg rfc6068 epg-config gnus-util
mm-decode mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils
mailheader sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr
mail-utils time-date network-stream puny nsm files-x cl-extra help-mode
ace-window avy slime-fancy slime-indentation slime-cl-indent cl-indent
slime-trace-dialog slime-fontifying-fu slime-package-fu slime-
references
slime-compiler-notes-tree advice slime-scratch slime-presentations
bridge slime-macrostep macrostep slime-mdot-fu slime-enclosing-context
slime-fuzzy slime-fancy-trace slime-fancy-inspector slime-c-p-c
slime-editing-commands slime-autodoc slime-repl slime-parse slime
easy-mmode apropos compile text-property-search etags fileloop
generator
xref project arc-mode archive-mode noutline outline icons pp comint
ansi-osc ansi-color ring hyperspec thingatpt ace-window-autoloads
avy-autoloads 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/x-win x-win term/common-win x-dnd 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 dbusbind inotify lcms2
dynamic-setting system-font-setting font-render-setting cairo
move-toolbar gtk x-toolkit xinput2 x multi-tty make-network-process
emacs)

Memory information:
((conses 16 122838 9467)
 (symbols 48 13323 2)
 (strings 32 45474 2514)
 (string-bytes 1 1178662)
 (vectors 16 23421)
 (vector-slots 8 302725 11017)
 (floats 8 55 59)
 (intervals 56 977 0)
 (buffers 984 21))


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