Convert symbol prettification into minor mode and global minor mode.

* etc/NEWS: Document new Prettify Symbols mode.

* lisp/progmodes/prog-mode.el (prettify-symbols-alist): Rename from
  `prog-prettify-symbols', and make a local defvar instead of defcustom.
  (prettify-symbols--keywords): Rename from `prog-prettify-symbols-alist'
  and make a local defvar.
  (prettify-symbols--compose-symbol): Rename from
  `prog--prettify-font-lock-compose-symbol'.
  (prettify-symbols--make-keywords): Rename from
  `prog-prettify-font-lock-symbols-keywords' and simplify.
  (prog-prettify-install): Remove.
  (prettify-symbols-mode): New minor mode, based on `prog-prettify-install'.
  (turn-on-prettify-symbols-mode): New function.
  (global-prettify-symbols-mode): New globalized minor mode.

* lisp/emacs-lisp/lisp-mode.el (lisp-mode-variables):
* lisp/progmodes/cfengine.el (cfengine3-mode):
* lisp/progmodes/perl-mode.el (perl-mode): Don't call `prog-prettify-install';
  set `prettify-symbols-alist' instead.

1 files changed, 4 insertions, 4 deletions

diff --git a/etc/NEWS b/etc/NEWS
index a2ef1c4fdd..a2f96f4bf9 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -2873,10 +2873,10 @@ should be derived.
 modes, e.g. (add-hook 'prog-mode-hook 'flyspell-prog-mode) to enable
 on-the-fly spell checking for comments and strings.
 
-**** New option, `prog-prettify-symbols' lets the user control symbol
-prettify (replacing a string like "lambda" with the Greek lambda
-character).  The mode derived from `prog-mode' must call
-`prog-prettify-install' with its own custom alist, which can be empty.
+**** New minor modes `prettify-symbols-mode' and
+`global-prettify-symbols-mode' let the user enable symbol
+prettification (replacing a string like "lambda" with the Greek lambda
+character).
 
 *** New hook `change-major-mode-after-body-hook', run by
 `run-mode-hooks' just before any other mode hooks.