1;;; novice.el --- handling of disabled commands ("novice mode") for Emacs
2
3;; Copyright (C) 1985, 1986, 1987, 1994, 2001, 2002, 2003, 2004,
4;;   2005, 2006, 2007 Free Software Foundation, Inc.
5
6;; Maintainer: FSF
7;; Keywords: internal, help
8
9;; This file is part of GNU Emacs.
10
11;; GNU Emacs is free software; you can redistribute it and/or modify
12;; it under the terms of the GNU General Public License as published by
13;; the Free Software Foundation; either version 2, or (at your option)
14;; any later version.
15
16;; GNU Emacs is distributed in the hope that it will be useful,
17;; but WITHOUT ANY WARRANTY; without even the implied warranty of
18;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
19;; GNU General Public License for more details.
20
21;; You should have received a copy of the GNU General Public License
22;; along with GNU Emacs; see the file COPYING.  If not, write to the
23;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
24;; Boston, MA 02110-1301, USA.
25
26;;; Commentary:
27
28;; This mode provides a hook which is, by default, attached to various
29;; putatively dangerous commands in a (probably futile) attempt to
30;; prevent lusers from shooting themselves in the feet.
31
32;;; Code:
33
34;; This function is called (by autoloading)
35;; to handle any disabled command.
36;; The command is found in this-command
37;; and the keys are returned by (this-command-keys).
38
39;;;###autoload
40(defvar disabled-command-function 'disabled-command-function
41  "Function to call to handle disabled commands.
42If nil, the feature is disabled, i.e., all commands work normally.")
43
44;;;###autoload
45(define-obsolete-variable-alias 'disabled-command-hook 'disabled-command-function "22.1")
46
47;; It is ok here to assume that this-command is a symbol
48;; because we won't get called otherwise.
49;;;###autoload
50(defun disabled-command-function (&rest ignore)
51  (let (char)
52    (save-window-excursion
53     (with-output-to-temp-buffer "*Disabled Command*"
54       (let ((keys (this-command-keys)))
55	 (if (or (eq (aref keys 0)
56		     (if (stringp keys)
57			 (aref "\M-x" 0)
58		       ?\M-x))
59		 (and (>= (length keys) 2)
60		      (eq (aref keys 0) meta-prefix-char)
61		      (eq (aref keys 1) ?x)))
62	     (princ (format "You have invoked the disabled command %s.\n"
63			    (symbol-name this-command)))
64	   (princ (format "You have typed %s, invoking disabled command %s.\n"
65			  (key-description keys) (symbol-name this-command)))))
66       ;; Print any special message saying why the command is disabled.
67       (if (stringp (get this-command 'disabled))
68	   (princ (get this-command 'disabled))
69	 (princ "It is disabled because new users often find it confusing.\n")
70	 (princ "Here's the first part of its description:\n\n")
71	 ;; Keep only the first paragraph of the documentation.
72	 (with-current-buffer "*Disabled Command*"
73	   (goto-char (point-max))
74	   (let ((start (point)))
75	     (save-excursion
76	       (princ (or (condition-case ()
77			      (documentation this-command)
78			    (error nil))
79			  "<< not documented >>")))
80	     (if (search-forward "\n\n" nil t)
81		 (delete-region (match-beginning 0) (point-max)))
82	     (goto-char (point-max))
83	     (indent-rigidly start (point) 3))))
84       (princ "\n\nDo you want to use this command anyway?\n\n")
85       (princ "You can now type
86y   to try it and enable it (no questions if you use it again).
87n   to cancel--don't try the command, and it remains disabled.
88SPC to try the command just this once, but leave it disabled.
89!   to try it, and enable all disabled commands for this session only.")
90       (save-excursion
91	(set-buffer standard-output)
92	(help-mode)))
93     (message "Type y, n, ! or SPC (the space bar): ")
94     (let ((cursor-in-echo-area t))
95       (while (progn (setq char (read-event))
96		     (or (not (numberp char))
97			 (not (memq (downcase char)
98				    '(?! ?y ?n ?\s ?\C-g)))))
99	 (ding)
100	 (message "Please type y, n, ! or SPC (the space bar): "))))
101    (setq char (downcase char))
102    (if (= char ?\C-g)
103	(setq quit-flag t))
104    (if (= char ?!)
105	(setq disabled-command-function nil))
106    (if (= char ?y)
107	(if (and user-init-file
108		 (not (string= "" user-init-file))
109		 (y-or-n-p "Enable command for future editing sessions also? "))
110	    (enable-command this-command)
111	  (put this-command 'disabled nil)))
112    (if (/= char ?n)
113	(call-interactively this-command))))
114
115;;;###autoload
116(defun enable-command (command)
117  "Allow COMMAND to be executed without special confirmation from now on.
118COMMAND must be a symbol.
119This command alters the user's .emacs file so that this will apply
120to future sessions."
121  (interactive "CEnable command: ")
122  (put command 'disabled nil)
123  (let ((init-file user-init-file)
124	(default-init-file
125	  (if (eq system-type 'ms-dos) "~/_emacs" "~/.emacs")))
126    (when (null init-file)
127      (if (or (file-exists-p default-init-file)
128	      (and (eq system-type 'windows-nt)
129		   (file-exists-p "~/_emacs")))
130	  ;; Started with -q, i.e. the file containing
131	  ;; enabled/disabled commands hasn't been read.  Saving
132	  ;; settings there would overwrite other settings.
133	  (error "Saving settings from \"emacs -q\" would overwrite existing customizations"))
134      (setq init-file default-init-file)
135      (if (and (not (file-exists-p init-file))
136	       (eq system-type 'windows-nt)
137	       (file-exists-p "~/_emacs"))
138	  (setq init-file "~/_emacs")))
139    (save-excursion
140      (set-buffer (find-file-noselect
141		   (substitute-in-file-name init-file)))
142      (goto-char (point-min))
143      (if (search-forward (concat "(put '" (symbol-name command) " ") nil t)
144	  (delete-region
145	   (progn (beginning-of-line) (point))
146	   (progn (forward-line 1) (point))))
147      ;; Explicitly enable, in case this command is disabled by default
148      ;; or in case the code we deleted was actually a comment.
149      (goto-char (point-max))
150      (insert "\n(put '" (symbol-name command) " 'disabled nil)\n")
151      (save-buffer))))
152
153;;;###autoload
154(defun disable-command (command)
155  "Require special confirmation to execute COMMAND from now on.
156COMMAND must be a symbol.
157This command alters the user's .emacs file so that this will apply
158to future sessions."
159  (interactive "CDisable command: ")
160  (if (not (commandp command))
161      (error "Invalid command name `%s'" command))
162  (put command 'disabled t)
163  (let ((init-file user-init-file)
164	(default-init-file
165	  (if (eq system-type 'ms-dos) "~/_emacs" "~/.emacs")))
166    (when (null init-file)
167      (if (or (file-exists-p default-init-file)
168	      (and (eq system-type 'windows-nt)
169		   (file-exists-p "~/_emacs")))
170	  ;; Started with -q, i.e. the file containing
171	  ;; enabled/disabled commands hasn't been read.  Saving
172	  ;; settings there would overwrite other settings.
173	  (error "Saving settings from \"emacs -q\" would overwrite existing customizations"))
174      (setq init-file default-init-file)
175      (if (and (not (file-exists-p init-file))
176	       (eq system-type 'windows-nt)
177	       (file-exists-p "~/_emacs"))
178	  (setq init-file "~/_emacs")))
179    (save-excursion
180      (set-buffer (find-file-noselect
181		   (substitute-in-file-name init-file)))
182      (goto-char (point-min))
183      (if (search-forward (concat "(put '" (symbol-name command) " ") nil t)
184	  (delete-region
185	   (progn (beginning-of-line) (point))
186	   (progn (forward-line 1) (point)))
187	(goto-char (point-max))
188	(insert ?\n))
189      (insert "(put '" (symbol-name command) " 'disabled t)\n")
190      (save-buffer))))
191
192(provide 'novice)
193
194;; arch-tag: f83c0f96-497e-4db6-a430-8703716c6dd9
195;;; novice.el ends here
196