lisp/novice.el

   1 ;;; novice.el --- handling of disabled commands ("novice mode") for Emacs.
   2
   3 ;; Copyright (C) 1985, 1986, 1987 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        (if (= (aref (this-command-keys) 0) ?\M-x)
  46            (princ "You have invoked the disabled command ")
  47          (princ "You have typed ")
  48          (princ (key-description (this-command-keys)))
  49          (princ ", invoking disabled command "))
  50        (princ this-command)
  51        (princ ":\n")
  52        ;; Print any special message saying why the command is disabled.
  53        (if (stringp (get this-command 'disabled))
  54            (princ (get this-command 'disabled)))
  55        (princ (or (condition-case ()
  56                       (documentation this-command)
  57                     (error nil))
  58                   "<< not documented >>"))
  59        ;; Keep only the first paragraph of the documentation.
  60        (save-excursion
  61          (set-buffer "*Help*")
  62          (goto-char (point-min))
  63          (if (search-forward "\n\n" nil t)
  64              (delete-region (1- (point)) (point-max))
  65            (goto-char (point-max))))
  66        (princ "\n\n")
  67        (princ "You can now type
  68 Space to try the command just this once,
  69       but leave it disabled,
  70 Y to try it and enable it (no questions if you use it again),
  71 N to do nothing (command remains disabled)."))
  72      (message "Type y, n or Space: ")
  73      (let ((cursor-in-echo-area t))
  74        (while (not (memq (setq char (downcase (read-char)))
  75                          '(?  ?y ?n)))
  76          (ding)
  77          (message "Please type y, n or Space: "))))
  78     (if (= char ?y)
  79         (if (y-or-n-p "Enable command for future editing sessions also? ")
  80             (enable-command this-command)
  81           (put this-command 'disabled nil)))
  82     (if (/= char ?n)
  83         (call-interactively this-command))))
  84
  85 ;;;###autoload
  86 (defun enable-command (command)
  87   "Allow COMMAND to be executed without special confirmation from now on.
  88 The user's .emacs file is altered so that this will apply
  89 to future sessions."
  90   (interactive "CEnable command: ")
  91   (put command 'disabled nil)
  92   (save-excursion
  93    (set-buffer (find-file-noselect (substitute-in-file-name "~/.emacs")))
  94    (goto-char (point-min))
  95    (if (search-forward (concat "(put '" (symbol-name command) " ") nil t)
  96        (delete-region
  97         (progn (beginning-of-line) (point))
  98         (progn (forward-line 1) (point)))
  99      ;; Must have been disabled by default.
 100      (goto-char (point-max))
 101      (insert "\n(put '" (symbol-name command) " 'disabled nil)\n"))
 102    (save-buffer)))
 103
 104 ;;;###autoload
 105 (defun disable-command (command)
 106   "Require special confirmation to execute COMMAND from now on.
 107 The user's .emacs file is altered so that this will apply
 108 to future sessions."
 109   (interactive "CDisable command: ")
 110   (put command 'disabled t)
 111   (save-excursion
 112    (set-buffer (find-file-noselect (substitute-in-file-name "~/.emacs")))
 113    (goto-char (point-min))
 114    (if (search-forward (concat "(put '" (symbol-name command) " ") nil t)
 115        (delete-region
 116         (progn (beginning-of-line) (point))
 117         (progn (forward-line 1) (point))))
 118    (goto-char (point-max))
 119    (insert "(put '" (symbol-name command) " 'disabled t)\n")
 120    (save-buffer)))
 121
 122 ;;; novice.el ends here