bug#61211: 28.2; Feature request; facility for dispatch type major mode

[Ikumi Keita]

I'd like to discuss dispatch functions or "superficial" major modes.
AUCTeX has the following major mode functions:
context-en-mode, context-nl-mode, japanese-latex-mode, japanese-plain-tex-mode
They only do language-specific set-ups and turn into context-mode,
latex-mode or plain-tex-mode eventually. In some aspects, they are
similar with dispatch functions `tex--guess-mode' and `TeX-tex-mode'
(AUCTeX) which guess a proper major mode and call it:
- They can be specified as `mode' tag of file local variable and entry
  of `auto-mode-alist'.
- They never hold their own `major-mode' value.
- When called, they eventually turn into another proper major mode.
For these reasons, they can be called "superficial" major modes.

Note that it isn't enough to define them like
(define-derived-mode japanese-latex-mode latex-mode "LaTeX"
  ...
  (setq major-mode 'latex-mode)
  ...)
because it doesn't respond to directory local variable entry of the form
((japanese-latex-mode
  ...))
in that case.

So I hope emacs to have facility to handle such superficial major modes
in a clean way.

Regards,
Ikumi Keita
#StandWithUkraine #StopWarInUkraine



In GNU Emacs 28.2 (build 1, x86_64-unknown-freebsd13.1, GTK+ Version 3.24.33, 
cairo version 1.17.4)
 of 2022-09-15 built on freebsd.vmware
Windowing system distributor 'The X.Org Foundation', version 11.0.12101004
System Description: 13.1-RELEASE-p5

Configured using:
 'configure --with-canna --with-canna-includes=/usr/local/canna/include
--with-canna-libraries=/usr/local/canna/lib --without-xim
--disable-largefile --without-modules --with-sound=yes
--with-file-notification=yes CFLAGS=-O3'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GNUTLS GSETTINGS HARFBUZZ JPEG JSON
LCMS2 LIBXML2 NOTIFY KQUEUE PDUMPER PNG RSVG SOUND THREADS TIFF
TOOLKIT_SCROLL_BARS X11 XDBE XIM XPM GTK3 ZLIB

Important settings:
  value of $EMACSLOADPATH: /home/keita/elisp:
  value of $LANG: ja_JP.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  shell-dirtrack-mode: t
  TeX-PDF-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  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
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t

Load-path shadows:
/home/keita/.emacs.d/elpa/transient-20230124.2013/transient hides 
/usr/local/share/emacs/28.2/lisp/transient
~/elisp/reftex-parse hides 
/usr/local/share/emacs/28.2/lisp/textmodes/reftex-parse
/home/keita/.emacs.d/elpa/soap-client-3.2.1/soap-inspect hides 
/usr/local/share/emacs/28.2/lisp/net/soap-inspect
/home/keita/.emacs.d/elpa/soap-client-3.2.1/soap-client hides 
/usr/local/share/emacs/28.2/lisp/net/soap-client

Features:
(pp shadow emacsbug mh-thread supercite regi mh-identity mh-letter
mh-comp sendmail reftex-sel reftex-ref reftex-parse preview reftex-dcr
reftex-auc reftex reftex-loaddefs reftex-vars tex-bar toolbar-x noutline
outline tex-mode shell pcomplete font-latex tex-jp latex easy-mmode
latex-flymake flymake-proc flymake project compile comint ansi-color
ring warnings tex-ispell tex-style tex texmathp latexenc mh-search qp
mm-archive smiley mail-extr mh-mime mh-gnus mh-alias multi-prompt crm
mh-show goto-addr thingatpt gnus-cite gnus-art mm-uu mml2015 mm-view
mml-smime smime dig gnus-sum shr svg dom gnus-group gnus-undo gnus-start
gnus-dbus dbus gnus-cloud nnimap nnmail mail-source utf7 netrc nnoo
gnus-spec gnus-int message dired dired-loaddefs rfc822 mml mml-sec
mm-decode mm-bodies mm-encode gmm-utils mailheader gnus-win gnus-range
gnus nnheader wid-edit mh-seq mh-inc hl-line mh-tool-bar mh-xface
mh-utils mh-folder which-func imenu gnus-util rmail rmail-loaddefs
mail-utils text-property-search mh-scan mh-e mh-compat mailabbrev
mh-buffers mh-loaddefs skeleton misearch multi-isearch conf-mode
mule-util kinsoku cl-extra help-mode parse-time iso8601 time-date
ucs-normalize epa derived epg rfc6068 epg-config url-http url-auth
mail-parse rfc2231 rfc2047 rfc2045 mm-util ietf-drums mail-prsvr url-gw
nsm rmc puny jka-compr twittering-mode advice xml edmacro kmacro
preview-latex tex-site canna-im 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 cl-seq eieio
eieio-core cl-macs eieio-loaddefs password-cache json subr-x map
url-vars seq byte-opt gv bytecomp byte-compile cconv cl-loaddefs cl-lib
japan-util 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 kqueue lcms2
dynamic-setting system-font-setting font-render-setting cairo
move-toolbar gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
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