Below is an improvement for conf-mode to deal with libconfig files.
Maybe this code could be added to the conf-mode.
;;; conf-config-mode.el --- Simple major mode for editing libconfig files -*- lexical-binding: t; -*-
;; Copyright (C) 2020 Vinicius José Latorre
;; Author: Vinicius José Latorre <
viniciusjl.gnu@gmail.com>
;; Keywords: libconfig
;; This file is NOT part of GNU Emacs.
;; GNU Emacs is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.
;; GNU Emacs is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
;; GNU General Public License for more details.
;; You should have received a copy of the GNU General Public License
;; along with GNU Emacs. If not, see <
https://www.gnu.org/licenses/>.
;;; Commentary:
;;
;; This mode is designed to edit libconfig files.
;; It derives from Daniel Pfeiffer's conf-mode (conf-toml-*).
;;
;; Follow the link below to see the libconfig documentation:
;;
https://hyperrealm.github.io/libconfig/;;
;; Libconfig is a simple library for processing structured configuration files.
;; This file format is more compact and more readable than XML. And unlike XML,
;; it is type-aware, so it is not necessary to do string parsing in application
;; code.
;;
;; Libconfig is very compact – a fraction of the size of the expat XML parser
;; library. This makes it well-suited for memory-constrained systems like
;; handheld devices.
;;
;; The library includes bindings for both the C and C++ languages. It works on
;; POSIX-compliant UNIX and UNIX-like systems (GNU/Linux, Mac OS X, FreeBSD),
;; Android, and Windows (2000, XP and later).
;;; Code:
(require 'conf-mode)
(defvar conf-config-mode-syntax-table
(let ((table (make-syntax-table conf-mode-syntax-table)))
;; string: " \t "
(modify-syntax-entry ?\" "\"" table)
(modify-syntax-entry ?\\ "\\" table)
;; script comment: # \n
(modify-syntax-entry ?# "<" table)
;; C++ comment style: /* */, // \n
(modify-syntax-entry ?/ ". 124" table)
(modify-syntax-entry ?* ". 23b" table)
;; override
(modify-syntax-entry ?\; "." table)
(modify-syntax-entry ?' "." table)
table)
"Syntax table in use in CONFIG style `conf-mode' buffers.")
(defvar conf-config-font-lock-keywords
'(;; setting: name = value, name : value
("\\_<\\([*A-Za-z][*A-Za-z0-9_-]*\\)\\_>\\s-*[=:]"
(1 'font-lock-variable-name-face nil t))
;; directive: @include "path"
("@include\\_>" 0 'font-lock-preprocessor-face)
;; optional: ;
(";" 0 'font-lock-builtin-face)
;; array: [ ], list: ( ), group: { }
("[][(){}]" 0 'font-lock-regexp-grouping-construct)
;; boolean values: true, false
("\\_<false\\|true\\_>" 0 'font-lock-keyword-face))
"Keywords to highlight in Conf CONFIG mode.")
;;;###autoload
(define-derived-mode conf-config-mode conf-mode "Conf[CONFIG]"
"Conf Mode starter for CONFIG files.
Comments start with `#' and \"assignments\" are with `=' or `:'.
For details see `conf-mode'. Example:
# Conf mode font-locks this right with \\[conf-config-mode]
value = \"some string\";
value : \"string\";"
(conf-mode-initialize "#" 'conf-config-font-lock-keywords)
(setq-local conf-assignment-column 0)
(setq-local conf-assignment-sign ?=))
(provide 'conf-config-mode)
;;; conf-config-mode.el ends here