bug#60983: 29.0.60; Tree-sitter user-level control

[Eli Zaretskii]

I started looking into providing user-level documentation for
tree-sitter based modes, and bumped into some issues:

 . How does one use treesit-font-lock-level?

   - It is not a customizable user option (unlike
     font-lock-maximum-decoration), so it cannot be set via
     customize-variable.  Is there a reason not to make it a
     defcustom?
   - It automatically becomes buffer-local when set, and OTOH setting
     it in a buffer does not produce fontifications according to the
     level, and neither does setting it in a mode hook.  So the only
     way to change its value is by using setq-default, which I don't
     think is the intent?
   - Should we make the variable a defcustom?
   - Should it be possible to customize it separately for each mode?
   - Should we allow to change the level and then call some function
     to re-fontify the current buffer according to the new level?

 . How does one change the indentation style in c-ts-mode?

   - There is a defcustom c-ts-mode-indent-style, but I don't think I
     see any difference in indentation of new code when I change the
     value.  What am I missing?

 . What commands are affected by treesit-defun-tactic?


In GNU Emacs 29.0.60 (build 238, i686-pc-mingw32) of 2023-01-20 built on
 HOME-C4E4A596F7
Repository revision: 472f142598566fbaeedcacaf9a9c757a1281c0c5
Repository branch: emacs-29
Windowing system distributor 'Microsoft Corp.', version 5.1.2600
System Description: Microsoft Windows XP Service Pack 3 (v5.1.0.2600)

Configured using:
 'configure -C --prefix=/d/usr --with-wide-int
 --enable-checking=yes,glyphs 'CFLAGS=-O0 -gdwarf-4 -g3''

Configured features:
ACL GIF GMP GNUTLS HARFBUZZ JPEG JSON LCMS2 LIBXML2 MODULES NOTIFY
W32NOTIFY PDUMPER PNG RSVG SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS TREE_SITTER WEBP XPM ZLIB

Important settings:
  value of $LANG: ENU
  locale-coding-system: cp1255

Major mode: C

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
  blink-cursor-mode: t
  line-number-mode: t
  indent-tabs-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 mailcap yank-media puny dired
dired-loaddefs rfc822 mml mml-sec password-cache epa derived epg rfc6068
epg-config gnus-util time-date subr-x mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader sendmail rfc2047
rfc2045 ietf-drums mm-util mail-prsvr mail-utils shortdoc
text-property-search misearch multi-isearch cl-extra cl-print thingatpt
help-fns radix-tree pp wid-edit descr-text help-mode c-ts-mode treesit
cl-seq vc-git diff-mode easy-mmode vc vc-dispatcher bug-reference
byte-opt gv bytecomp byte-compile cc-mode cc-fonts cc-guess cc-menus
cc-cmds cc-styles cc-align cc-engine cc-vars cc-defs cl-loaddefs cl-lib
rmc iso-transl tooltip cconv eldoc paren electric uniquify ediff-hook
vc-hooks lisp-float-type elisp-mode mwheel dos-w32 ls-lisp disp-table
term/w32-win w32-win w32-vars 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 w32notify w32 lcms2 multi-tty
make-network-process emacs)

Memory information:
((conses 16 107446 10610)
 (symbols 48 10355 0)
 (strings 16 33788 3445)
 (string-bytes 1 1014069)
 (vectors 16 17439)
 (vector-slots 8 223440 13934)
 (floats 8 91 195)
 (intervals 40 3548 140)
 (buffers 888 14))