bug#19690: [PATCH] Clarify mode switch messages to avoid potential confusion

[Kelly Dean <kelly@prtime.org>]

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This is only a feature enhancement, not a bug report.

When first learning Emacs, I was often confused about whether a minor mode was enabled globally or just in the current buffer. For example, show-paren-mode is global, but whitespace-mode is buffer-local (unless you use global-whitespace-mode). I still sometimes misinterpret this.

Sure, the user can find out, but the attached patch helps make things clear, by indicating if the mode being toggled is buffer-local. It will be especially helpful for alerting users in the relatively rare cases when they toggle a normally-global minor mode that has been set buffer-locally.

BTW, in define-minor-mode, last-message is indirected, but I don't see any reason not to just use it directly.


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--- emacs-24.4/lisp/emacs-lisp/easy-mmode.el
+++ emacs-24.4/lisp/emacs-lisp/easy-mmode.el
@@ -279,14 +279,23 @@
            (if (called-interactively-p 'any)
                (progn
                  ,(if (and globalp (symbolp mode))
+		      ;; Unnecessary but harmless if mode set buffer-locally
                       `(customize-mark-as-set ',mode))
                  ;; Avoid overwriting a message shown by the body,
                  ;; but do overwrite previous messages.
                  (unless (and (current-message)
                               (not (equal ,last-message
                                           (current-message))))
-                   (message ,(format "%s %%sabled" pretty-name)
-                            (if ,mode "en" "dis")))))
+                   (let ((local
+			  ,(if globalp
+			       (if (symbolp mode)
+				   `(if (assq ',mode (buffer-local-variables))
+					" in current buffer"
+				      "")
+				 "")
+			     " in current buffer")))
+		     (message ,(format "%s %%sabled%%s" pretty-name)
+			      (if ,mode "en" "dis") local)))))
 	   ,@(when after-hook `(,after-hook)))
 	 (force-mode-line-update)
 	 ;; Return the new setting.