bug#51629: 29.0.50; State of outline minor mode buttons not synchronized

[Matthias Meulien]

1. Set `outline-minor-mode-use-buttons' to true (I've done it through
`customize-group')

2. Make sure that `emacs-lisp-mode-hook' enables outline-minor-mode
(I've done it through `add-hook')

3. Visit a .el file, say lisp/outline.el from Emacs sources

4. Observe that buttons aren't displayed.

If one starts toggling headings visibility using outline-minor-mode key
bindings, some buttons are displayed. Eg after "C-c @ C-t" followed by
"C-c @ C-s" I got:

In GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.24, cairo 
version 1.16.0)
 of 2021-11-06 built on carbon
Repository revision: 6d406aee501cb6462075149683e492956ce9b7f3
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12011000
System Description: Debian GNU/Linux 11 (bullseye)

Configured using:
 'configure --with-native-compilation'

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

Important settings:
  value of $LANG: fr_FR.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: ELisp/l

Minor modes in effect:
  display-line-numbers-mode: t
  highlight-changes-mode: t
  shell-dirtrack-mode: t
  bug-reference-prog-mode: t
  minions-mode: t
  outline-minor-mode: t
  desktop-save-mode: t
  save-place-mode: t
  electric-pair-mode: t
  icomplete-mode: t
  global-so-long-mode: t
  global-auto-revert-mode: t
  auto-insert-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-mode: t
  electric-layout-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tab-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  window-divider-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t
  abbrev-mode: t

Load-path shadows:
/home/matthias/.config/emacs/elpa/transient-20211029.1405/transient hides 
/usr/local/share/emacs/29.0.50/lisp/transient
/home/matthias/.config/emacs/elpa/dictionary-20201001.1727/dictionary hides 
/usr/local/share/emacs/29.0.50/lisp/net/dictionary

Features:
(smiley gnus-bcklg nndoc gnus-dup mm-archive url-cache crm debbugs-gnu
debbugs soap-client url-http url-auth url-gw rng-xsd xsd-regexp misearch
multi-isearch mailalias smtpmail shortdoc dabbrev shadow sort gnus-cite
mail-extr emacsbug sendmail gnus-async qp gnus-ml gnus-topic nndraft
nnmh nnfolder utf-7 epa-file gnutls network-stream nsm gnus-agent
gnus-srvr gnus-score score-mode nnvirtual gnus-msg gnus-cache kmacro
two-column vc-mtn vc-hg vc-bzr vc-src vc-sccs vc-svn vc-cvs vc-rcs
cl-print help-fns radix-tree allout cus-start smerge-mode diff pcase
whitespace log-view pcvs-util hl-line yaml-mode flymake-proc flymake
project python tramp-sh tramp tramp-loaddefs trampver tramp-integration
files-x tramp-compat ls-lisp thai-util thai-word lao-util ox-odt rng-loc
rng-uri rng-parse rng-match rng-dt rng-util rng-pttrn nxml-parse nxml-ns
nxml-enc xmltok nxml-util ox-latex ox-icalendar org-agenda ox-html table
ox-ascii ox-publish ox org-element avl-tree generator ol-eww eww xdg
url-queue mm-url ol-rmail ol-mhe ol-irc ol-info ol-gnus nnselect
gnus-search eieio-opt speedbar ezimage dframe gnus-art mm-uu mml2015
mm-view mml-smime smime dig gnus-sum shr kinsoku svg dom ol-docview
doc-view image-mode exif ol-bibtex ol-bbdb ol-w3m ol-doi org-link-doi
enriched disp-table facemenu view dired-aux mule-util jka-compr
display-line-numbers hilit-chg flyspell reftex-dcr reftex
reftex-loaddefs reftex-vars tex-mode compile shell bug-reference
goto-addr add-log vc-dir ewoc vc avoid minions carbon-custom cus-edit
cus-load gnus-demon nntp gnus-group gnus-undo gnus-start gnus-dbus dbus
xml gnus-cloud nnimap nnmail mail-source utf7 netrc parse-time gnus-spec
gnus-win nnoo gnus-int gnus-range message rmc puny rfc822 mml mml-sec
epa derived epg rfc6068 epg-config mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader gnus nnheader
gnus-util rmail rmail-loaddefs rfc2047 rfc2045 ietf-drums mail-utils
mm-util mail-prsvr wid-edit gnus-dired dired-x dired dired-loaddefs
org-capture org-refile org ob ob-tangle ob-ref ob-lob ob-table ob-exp
org-macro org-footnote org-src ob-comint org-pcomplete pcomplete comint
ansi-color ring org-list org-faces org-entities org-version
ob-emacs-lisp ob-core ob-eval org-table oc-basic bibtex iso8601 ol
org-keys oc org-compat org-macs org-loaddefs format-spec find-func
cal-menu calendar cal-loaddefs dictionary link connection advice
markdown-mode edit-indirect color thingatpt noutline outline skeleton
find-file vc-git diff-mode easy-mmode vc-dispatcher ispell time-date
desktop frameset server bookmark text-property-search pp saveplace
elec-pair icomplete so-long autorevert filenotify autoinsert cc-mode
cc-fonts cc-guess cc-menus cc-cmds cc-styles cc-align cc-engine cc-vars
cc-defs generic-x face-remap proof-site proof-autoloads info package
browse-url url url-proxy url-privacy url-expand url-methods url-history
url-cookie url-domsuf url-util mailcap url-handlers url-parse
auth-source eieio eieio-core eieio-loaddefs password-cache json map
url-vars comp comp-cstr warnings rx cl-seq cl-macs cl-extra help-mode
seq gv subr-x byte-opt bytecomp byte-compile cconv cl-loaddefs cl-lib
iso-transl tooltip 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 cl-generic
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 simple abbrev obarray
cl-preloaded nadvice button loaddefs faces cus-face macroexp files
window text-properties overlay sha1 md5 base64 format env code-pages
mule custom widget hashtable-print-readable backquote threads dbusbind
inotify lcms2 dynamic-setting system-font-setting font-render-setting
cairo move-toolbar gtk x-toolkit x multi-tty make-network-process
native-compile emacs)

Memory information:
((conses 16 1112679 177861)
 (symbols 48 39281 10)
 (strings 32 247990 48587)
 (string-bytes 1 8130967)
 (vectors 16 89668)
 (vector-slots 8 1836287 61261)
 (floats 8 3248 1028)
 (intervals 56 21053 2105)
 (buffers 992 66))