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 the
  22 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  23 ;; Boston, MA 02111-1307, USA.
  24
  25 ;;; Commentary:
  26
  27 ;; This mode provides a hook which is, by default, attached to various
  28 ;; putatively dangerous commands in a (probably futile) attempt to
  29 ;; prevent lusers from shooting themselves in the feet.
  30
  31 ;;; Code:
  32
  33 ;; This function is called (by autoloading)
  34 ;; to handle any disabled command.
  35 ;; The command is found in this-command
  36 ;; and the keys are returned by (this-command-keys).
  37
  38 ;;;###autoload
  39 (setq disabled-command-hook 'disabled-command-hook)
  40
  41 ;;;###autoload
  42 (defun disabled-command-hook (&rest ignore)
  43   (let (char)
  44     (save-window-excursion
  45      (with-output-to-temp-buffer "*Help*"
  46        (let ((keys (this-command-keys)))
  47          (if (or (eq (aref keys 0)
  48                      (if (stringp keys)
  49                          (aref "\M-x" 0)
  50                        ?\M-x))
  51                  (and (>= (length keys) 2)
  52                       (eq (aref keys 0) meta-prefix-char)
  53                       (eq (aref keys 1) ?x)))
  54              (princ "You have invoked the disabled command ")
  55            (princ "You have typed ")
  56            (princ (key-description keys))
  57            (princ ", invoking disabled command ")))
  58        (princ this-command)
  59        (princ ":\n")
  60        ;; Print any special message saying why the command is disabled.
  61        (if (stringp (get this-command 'disabled))
  62            (princ (get this-command 'disabled)))
  63        (princ (or (condition-case ()
  64                       (documentation this-command)
  65                     (error nil))
  66                   "<< not documented >>"))
  67        ;; Keep only the first paragraph of the documentation.
  68        (save-excursion
  69          (set-buffer "*Help*")
  70          (goto-char (point-min))
  71          (if (search-forward "\n\n" nil t)
  72              (delete-region (1- (point)) (point-max))
  73            (goto-char (point-max))))
  74        (princ "\n\n")
  75        (princ "You can now type
  76 Space to try the command just this once,
  77       but leave it disabled,
  78 Y to try it and enable it (no questions if you use it again),
  79 N to do nothing (command remains disabled).")
  80        (save-excursion
  81         (set-buffer standard-output)
  82         (help-mode)))
  83      (message "Type y, n or Space: ")
  84      (let ((cursor-in-echo-area t))
  85        (while (not (memq (setq char (downcase (read-char)))
  86                          '(?  ?y ?n)))
  87          (ding)
  88          (message "Please type y, n or Space: "))))
  89     (if (= char ?y)
  90         (if (and user-init-file
  91                  (not (string= "" user-init-file))
  92                  (y-or-n-p "Enable command for future editing sessions also? "))
  93             (enable-command this-command)
  94           (put this-command 'disabled nil)))
  95     (if (/= char ?n)
  96         (call-interactively this-command))))
  97
  98 ;;;###autoload
  99 (defun enable-command (command)
 100   "Allow COMMAND to be executed without special confirmation from now on.
 101 The user's .emacs file is altered so that this will apply
 102 to future sessions."
 103   (interactive "CEnable command: ")
 104   (put command 'disabled nil)
 105   (save-excursion
 106    (set-buffer (find-file-noselect
 107                 (substitute-in-file-name user-init-file)))
 108    (goto-char (point-min))
 109    (if (search-forward (concat "(put '" (symbol-name command) " ") nil t)
 110        (delete-region
 111         (progn (beginning-of-line) (point))
 112         (progn (forward-line 1) (point))))
 113    ;; Explicitly enable, in case this command is disabled by default
 114    ;; or in case the code we deleted was actually a comment.
 115    (goto-char (point-max))
 116    (insert "\n(put '" (symbol-name command) " 'disabled nil)\n")
 117    (save-buffer)))
 118
 119 ;;;###autoload
 120 (defun disable-command (command)
 121   "Require special confirmation to execute COMMAND from now on.
 122 The user's .emacs file is altered so that this will apply
 123 to future sessions."
 124   (interactive "CDisable command: ")
 125   (if (not (commandp command))
 126       (error "Invalid command name `%s'" command))
 127   (put command 'disabled t)
 128   (save-excursion
 129    (set-buffer (find-file-noselect
 130                 (substitute-in-file-name user-init-file)))
 131    (goto-char (point-min))
 132    (if (search-forward (concat "(put '" (symbol-name command) " ") nil t)
 133        (delete-region
 134         (progn (beginning-of-line) (point))
 135         (progn (forward-line 1) (point))))
 136    (goto-char (point-max))
 137    (insert "\n(put '" (symbol-name command) " 'disabled t)\n")
 138    (save-buffer)))
 139
 140 ;;; novice.el ends here