lisp/novice.el

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