lisp/novice.el

   1 ;;; novice.el --- handling of disabled commands ("novice mode") for Emacs
   2
   3 ;; Copyright (C) 1985, 1986, 1987, 1994, 2002, 2004
   4 ;;   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., 59 Temple Place - Suite 330,
  24 ;; Boston, MA 02111-1307, 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.
  42 If nil, the feature is disabled, i.e., all commands work normally.")
  43
  44 ;;;###autoload
  45 (defvaralias 'disabled-command-hook 'disabled-command-function)
  46 ;;;###autoload (make-obsolete-variable 'disabled-command-hook 'disabled-command-function "22.1")
  47
  48 ;;;###autoload
  49 (defun disabled-command-function (&rest ignore)
  50   (let (char)
  51     (save-window-excursion
  52      (with-output-to-temp-buffer "*Help*"
  53        (let ((keys (this-command-keys)))
  54          (if (or (eq (aref keys 0)
  55                      (if (stringp keys)
  56                          (aref "\M-x" 0)
  57                        ?\M-x))
  58                  (and (>= (length keys) 2)
  59                       (eq (aref keys 0) meta-prefix-char)
  60                       (eq (aref keys 1) ?x)))
  61              (princ (format "You have invoked the disabled command %s.\n"
  62                             (symbol-name this-command)))
  63            (princ (format "You have typed %s, invoking disabled command %s.\n"
  64                           (key-description keys) (symbol-name this-command)))))
  65        ;; Print any special message saying why the command is disabled.
  66        (if (stringp (get this-command 'disabled))
  67            (princ (get this-command 'disabled))
  68          (princ "It is disabled because new users often find it confusing.\n")
  69          (princ "Here's the first part of its description:\n\n")
  70          ;; Keep only the first paragraph of the documentation.
  71          (with-current-buffer "*Help*"
  72            (goto-char (point-max))
  73            (let ((start (point)))
  74              (save-excursion
  75                (princ (or (condition-case ()
  76                               (documentation this-command)
  77                             (error nil))
  78                           "<< not documented >>")))
  79              (if (search-forward "\n\n" nil t)
  80                  (delete-region (match-beginning 0) (point-max)))
  81              (goto-char (point-max))
  82              (indent-rigidly start (point) 3))))
  83        (princ "\n\nDo you want to use this command anyway?\n\n")
  84        (princ "You can now type
  85 y   to try it and enable it (no questions if you use it again).
  86 n   to cancel--don't try the command, and it remains disabled.
  87 SPC to try the command just this once, but leave it disabled.
  88 !   to try it, and enable all disabled commands for this session only.")
  89        (save-excursion
  90         (set-buffer standard-output)
  91         (help-mode)))
  92      (message "Type y, n, ! or SPC (the space bar): ")
  93      (let ((cursor-in-echo-area t))
  94        (while (not (memq (setq char (downcase (read-char)))
  95                          '(?! ?y ?n ?\ )))
  96          (ding)
  97          (message "Please type y, n, ! or SPC (the space bar): "))))
  98     (if (= char ?!)
  99         (setq disabled-command-function nil))
 100     (if (= char ?y)
 101         (if (and user-init-file
 102                  (not (string= "" user-init-file))
 103                  (y-or-n-p "Enable command for future editing sessions also? "))
 104             (enable-command this-command)
 105           (put this-command 'disabled nil)))
 106     (if (/= char ?n)
 107         (call-interactively this-command))))
 108
 109 ;;;###autoload
 110 (defun enable-command (command)
 111   "Allow COMMAND to be executed without special confirmation from now on.
 112 COMMAND must be a symbol.
 113 This command alters the user's .emacs file so that this will apply
 114 to future sessions."
 115   (interactive "CEnable command: ")
 116   (put command 'disabled nil)
 117   (let ((init-file user-init-file)
 118         (default-init-file
 119           (if (eq system-type 'ms-dos) "~/_emacs" "~/.emacs")))
 120     (when (null init-file)
 121       (if (or (file-exists-p default-init-file)
 122               (and (eq system-type 'windows-nt)
 123                    (file-exists-p "~/_emacs")))
 124           ;; Started with -q, i.e. the file containing
 125           ;; enabled/disabled commands hasn't been read.  Saving
 126           ;; settings there would overwrite other settings.
 127           (error "Saving settings from \"emacs -q\" would overwrite existing customizations"))
 128       (setq init-file default-init-file)
 129       (if (and (not (file-exists-p init-file))
 130                (eq system-type 'windows-nt)
 131                (file-exists-p "~/_emacs"))
 132           (setq init-file "~/_emacs")))
 133     (save-excursion
 134       (set-buffer (find-file-noselect
 135                    (substitute-in-file-name init-file)))
 136       (goto-char (point-min))
 137       (if (search-forward (concat "(put '" (symbol-name command) " ") nil t)
 138           (delete-region
 139            (progn (beginning-of-line) (point))
 140            (progn (forward-line 1) (point))))
 141       ;; Explicitly enable, in case this command is disabled by default
 142       ;; or in case the code we deleted was actually a comment.
 143       (goto-char (point-max))
 144       (insert "\n(put '" (symbol-name command) " 'disabled nil)\n")
 145       (save-buffer))))
 146
 147 ;;;###autoload
 148 (defun disable-command (command)
 149   "Require special confirmation to execute COMMAND from now on.
 150 COMMAND must be a symbol.
 151 This command alters the user's .emacs file so that this will apply
 152 to future sessions."
 153   (interactive "CDisable command: ")
 154   (if (not (commandp command))
 155       (error "Invalid command name `%s'" command))
 156   (put command 'disabled t)
 157   (let ((init-file user-init-file)
 158         (default-init-file
 159           (if (eq system-type 'ms-dos) "~/_emacs" "~/.emacs")))
 160     (when (null init-file)
 161       (if (or (file-exists-p default-init-file)
 162               (and (eq system-type 'windows-nt)
 163                    (file-exists-p "~/_emacs")))
 164           ;; Started with -q, i.e. the file containing
 165           ;; enabled/disabled commands hasn't been read.  Saving
 166           ;; settings there would overwrite other settings.
 167           (error "Saving settings from \"emacs -q\" would overwrite existing customizations"))
 168       (setq init-file default-init-file)
 169       (if (and (not (file-exists-p init-file))
 170                (eq system-type 'windows-nt)
 171                (file-exists-p "~/_emacs"))
 172           (setq init-file "~/_emacs")))
 173     (save-excursion
 174       (set-buffer (find-file-noselect
 175                    (substitute-in-file-name init-file)))
 176       (goto-char (point-min))
 177       (if (search-forward (concat "(put '" (symbol-name command) " ") nil t)
 178           (delete-region
 179            (progn (beginning-of-line) (point))
 180            (progn (forward-line 1) (point))))
 181       (goto-char (point-max))
 182       (insert "\n(put '" (symbol-name command) " 'disabled t)\n")
 183       (save-buffer))))
 184
 185 (provide 'novice)
 186
 187 ;; arch-tag: f83c0f96-497e-4db6-a430-8703716c6dd9
 188 ;;; novice.el ends here