Font-lock FDO desktop files correctly

Single and double quotes do not have a special meaning in
desktop files.
https://standards.freedesktop.org/desktop-entry-spec/latest/
* etc/NEWS: Mention new mode.
* lisp/files.el (auto-mode-alist): Split out an entry for handling
the .desktop extension with conf-desktop-mode.
* lisp/textmodes/conf-mode.el (conf-desktop-font-lock-keywords): New
variable with rules for booleans and format specifiers.
(conf-unix-mode): Remove desktop file entry example from docstring.
(conf-desktop-mode): New derived major mode.

1 files changed, 22 insertions, 10 deletions

diff --git a/lisp/textmodes/conf-mode.el b/lisp/textmodes/conf-mode.el
index b420aaa2467..d03ee5eb314 100644
--- a/lisp/textmodes/conf-mode.el
+++ b/lisp/textmodes/conf-mode.el
@@ -262,6 +262,12 @@ This variable is best set in the file local variables, or through
     ("\\_<false\\|true\\_>" 0 'font-lock-keyword-face))
   "Keywords to highlight in Conf TOML mode.")
 
+(defvar conf-desktop-font-lock-keywords
+  `(,@conf-font-lock-keywords
+    ("\\_<false\\|true\\_>" 0 'font-lock-constant-face)
+    ("\\_<%[uUfFick%]\\_>" 0 'font-lock-constant-face))
+  "Keywords to highlight in Conf Desktop mode.")
+
 (defvar conf-assignment-sign ?=
   "Sign used for assignments (char or string).")
 
@@ -449,16 +455,7 @@ The optional arg FONT-LOCK is the value for FONT-LOCK-KEYWORDS."
 ;;;###autoload
 (define-derived-mode conf-unix-mode conf-mode "Conf[Unix]"
   "Conf Mode starter for Unix style Conf files.
-Comments start with `#'.
-For details see `conf-mode'.  Example:
-
-# Conf mode font-locks this right on Unix and with \\[conf-unix-mode]
-
-[Desktop Entry]
-         Encoding=UTF-8
-         Name=The GIMP
-         Name[ca]=El GIMP
-         Name[cs]=GIMP"
+Comments start with `#'.  For details see `conf-mode'."
   (conf-mode-initialize "#"))
 
 ;;;###autoload
@@ -677,6 +674,21 @@ value = \"some string\""
   (setq-local conf-assignment-column 0)
   (setq-local conf-assignment-sign ?=))
 
+;;;###autoload
+(define-derived-mode conf-desktop-mode conf-unix-mode "Conf[Desktop]"
+  "Conf Mode started for freedesktop.org Desktop files.
+Comments start with `#' and \"assignments\" are with `='.
+For details see `conf-mode'.
+
+# Conf mode font-locks this correctly with \\[conf-desktop-mode]
+        [Desktop Entry]
+        Name=GNU Image Manipulation Program
+        Name[oc]=Editor d'imatge GIMP
+        Exec=gimp-2.8 %U
+        Terminal=false"
+  (conf-mode-initialize "#" 'conf-desktop-font-lock-keywords)
+  (conf-quote-normal nil))
+
 (provide 'conf-mode)
 
 ;;; conf-mode.el ends here