lisp/novice.el

   1 ;;; novice.el --- handling of disabled commands ("novice mode") for Emacs.
   2
   3 ;; Copyright (C) 1985, 1986, 1987, 1994 Free Software Foundation, Inc.
   4
   5 ;; Maintainer: FSF
   6 ;; Keywords: internal, help
   7
   8 ;; This file is part of GNU Emacs.
   9
  10 ;; GNU Emacs is free software; you can redistribute it and/or modify
  11 ;; it under the terms of the GNU General Public License as published by
  12 ;; the Free Software Foundation; either version 2, or (at your option)
  13 ;; any later version.
  14
  15 ;; GNU Emacs is distributed in the hope that it will be useful,
  16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 ;; GNU General Public License for more details.
  19
  20 ;; You should have received a copy of the GNU General Public License
  21 ;; along with GNU Emacs; see the file COPYING.  If not, write to
  22 ;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
  23
  24 ;;; Commentary:
  25
  26 ;; This mode provides a hook which is, by default, attached to various
  27 ;; putatively dangerous commands in a (probably futile) attempt to
  28 ;; prevent lusers from shooting themselves in the feet.
  29
  30 ;;; Code:
  31
  32 ;; This function is called (by autoloading)
  33 ;; to handle any disabled command.
  34 ;; The command is found in this-command
  35 ;; and the keys are returned by (this-command-keys).
  36
  37 ;;;###autoload
  38 (setq disabled-command-hook 'disabled-command-hook)
  39
  40 ;;;###autoload
  41 (defun disabled-command-hook (&rest ignore)
  42   (let (char)
  43     (save-window-excursion
  44      (with-output-to-temp-buffer "*Help*"
  45        (let ((keys (this-command-keys)))
  46          (if (or (eq (aref keys 0)
  47                      (if (stringp keys)
  48                          (aref "\M-x" 0)
  49                        ?\M-x))
  50                  (and (>= (length keys) 2)
  51                       (eq (aref keys 0) meta-prefix-char)
  52                       (eq (aref keys 1) ?x)))
  53              (princ "You have invoked the disabled command ")
  54            (princ "You have typed ")
  55            (princ (key-description keys))
  56            (princ ", invoking disabled command ")))
  57        (princ this-command)
  58        (princ ":\n")
  59        ;; Print any special message saying why the command is disabled.
  60        (if (stringp (get this-command 'disabled))
  61            (princ (get this-command 'disabled)))
  62        (princ (or (condition-case ()
  63                       (documentation this-command)
  64                     (error nil))
  65                   "<< not documented >>"))
  66        ;; Keep only the first paragraph of the documentation.
  67        (save-excursion
  68          (set-buffer "*Help*")
  69          (goto-char (point-min))
  70          (if (search-forward "\n\n" nil t)
  71              (delete-region (1- (point)) (point-max))
  72            (goto-char (point-max))))
  73        (princ "\n\n")
  74        (princ "You can now type
  75 Space to try the command just this once,
  76       but leave it disabled,
  77 Y to try it and enable it (no questions if you use it again),
  78 N to do nothing (command remains disabled).")
  79        (save-excursion
  80         (set-buffer standard-output)
  81         (help-mode)))
  82      (message "Type y, n or Space: ")
  83      (let ((cursor-in-echo-area t))
  84        (while (not (memq (setq char (downcase (read-char)))
  85                          '(?  ?y ?n)))
  86          (ding)
  87          (message "Please type y, n or Space: "))))
  88     (if (= char ?y)
  89         (if (and user-init-file
  90                  (not (string= "" user-init-file))
  91                  (y-or-n-p "Enable command for future editing sessions also? "))
  92             (enable-command this-command)
  93           (put this-command 'disabled nil)))
  94     (if (/= char ?n)
  95         (call-interactively this-command))))
  96
  97 ;;;###autoload
  98 (defun enable-command (command)
  99   "Allow COMMAND to be executed without special confirmation from now on.
 100 The user's .emacs file is altered so that this will apply
 101 to future sessions."
 102   (interactive "CEnable command: ")
 103   (put command 'disabled nil)
 104   (save-excursion
 105    (set-buffer (find-file-noselect
 106                 (substitute-in-file-name user-init-file)))
 107    (goto-char (point-min))
 108    (if (search-forward (concat "(put '" (symbol-name command) " ") nil t)
 109        (delete-region
 110         (progn (beginning-of-line) (point))
 111         (progn (forward-line 1) (point))))
 112    ;; Explicitly enable, in case this command is disabled by default
 113    ;; or in case the code we deleted was actually a comment.
 114    (goto-char (point-max))
 115    (insert "\n(put '" (symbol-name command) " 'disabled nil)\n")
 116    (save-buffer)))
 117
 118 ;;;###autoload
 119 (defun disable-command (command)
 120   "Require special confirmation to execute COMMAND from now on.
 121 The user's .emacs file is altered so that this will apply
 122 to future sessions."
 123   (interactive "CDisable command: ")
 124   (if (not (commandp command))
 125       (error "Invalid command name `%s'" command))
 126   (put command 'disabled t)
 127   (save-excursion
 128    (set-buffer (find-file-noselect
 129                 (substitute-in-file-name user-init-file)))
 130    (goto-char (point-min))
 131    (if (search-forward (concat "(put '" (symbol-name command) " ") nil t)
 132        (delete-region
 133         (progn (beginning-of-line) (point))
 134         (progn (forward-line 1) (point))))
 135    (goto-char (point-max))
 136    (insert "\n(put '" (symbol-name command) " 'disabled t)\n")
 137    (save-buffer)))
 138
 139 ;;; novice.el ends here