lisp/gnus/gnus-undo.el

   1 ;;; gnus-undo.el --- minor mode for undoing in Gnus
   2 ;; Copyright (C) 1996,97,98 Free Software Foundation, Inc.
   3
   4 ;; Author: Lars Magne Ingebrigtsen <larsi@gnus.org>
   5 ;; Keywords: news
   6
   7 ;; This file is part of GNU Emacs.
   8
   9 ;; GNU Emacs is free software; you can redistribute it and/or modify
  10 ;; it under the terms of the GNU General Public License as published by
  11 ;; the Free Software Foundation; either version 2, or (at your option)
  12 ;; any later version.
  13
  14 ;; GNU Emacs is distributed in the hope that it will be useful,
  15 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  16 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  17 ;; GNU General Public License for more details.
  18
  19 ;; You should have received a copy of the GNU General Public License
  20 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  21 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  22 ;; Boston, MA 02111-1307, USA.
  23
  24 ;;; Commentary:
  25
  26 ;; This package allows arbitrary undoing in Gnus buffers.  As all the
  27 ;; Gnus buffers aren't very text-oriented (what is in the buffers is
  28 ;; just some arbitrary representation of the actual data), normal Emacs
  29 ;; undoing doesn't work at all for Gnus.
  30 ;;
  31 ;; This package works by letting Gnus register functions for reversing
  32 ;; actions, and then calling these functions when the user pushes the
  33 ;; `undo' key.  As with normal `undo', there it is possible to set
  34 ;; undo boundaries and so on.
  35 ;;
  36 ;; Internally, the undo sequence is represented by the
  37 ;; `gnus-undo-actions' list, where each element is a list of functions
  38 ;; to be called, in sequence, to undo some action.  (An "action" is a
  39 ;; collection of functions.)
  40 ;;
  41 ;; For instance, a function for killing a group will call
  42 ;; `gnus-undo-register' with a function that un-kills the group.  This
  43 ;; package will put that function into an action.
  44
  45 ;;; Code:
  46
  47 (eval-when-compile (require 'cl))
  48
  49 (eval-when-compile (require 'cl))
  50
  51 (require 'gnus-util)
  52 (require 'gnus)
  53 (require 'custom)
  54
  55 (defgroup gnus-undo nil
  56   "Undoing in Gnus buffers."
  57   :group 'gnus)
  58
  59 (defcustom gnus-undo-limit 2000
  60   "The number of undoable actions recorded."
  61   :type 'integer
  62   :group 'gnus-undo)
  63
  64 (defcustom gnus-undo-mode nil
  65   "Minor mode for undoing in Gnus buffers."
  66   :type 'boolean
  67   :group 'gnus-undo)
  68
  69 (defcustom gnus-undo-mode-hook nil
  70   "Hook called in all `gnus-undo-mode' buffers."
  71   :type 'hook
  72   :group 'gnus-undo)
  73
  74 ;;; Internal variables.
  75
  76 (defvar gnus-undo-actions nil)
  77 (defvar gnus-undo-boundary t)
  78 (defvar gnus-undo-last nil)
  79 (defvar gnus-undo-boundary-inhibit nil)
  80
  81 ;;; Minor mode definition.
  82
  83 (defvar gnus-undo-mode-map nil)
  84
  85 (unless gnus-undo-mode-map
  86   (setq gnus-undo-mode-map (make-sparse-keymap))
  87
  88   (gnus-define-keys gnus-undo-mode-map
  89    "\M-\C-_"     gnus-undo
  90    "\C-_"        gnus-undo
  91    "\C-xu"       gnus-undo
  92    ;; many people are used to type `C-/' on X terminals and get `C-_'.
  93    [(control /)] gnus-undo))
  94
  95 (defun gnus-undo-make-menu-bar ()
  96   ;; This is disabled for the time being.
  97   (when nil
  98     (define-key-after (current-local-map) [menu-bar file gnus-undo]
  99       (cons "Undo" 'gnus-undo-actions)
 100       [menu-bar file whatever])))
 101
 102 (defun gnus-undo-mode (&optional arg)
 103   "Minor mode for providing `undo' in Gnus buffers.
 104
 105 \\{gnus-undo-mode-map}"
 106   (interactive "P")
 107   (set (make-local-variable 'gnus-undo-mode)
 108        (if (null arg) (not gnus-undo-mode)
 109          (> (prefix-numeric-value arg) 0)))
 110   (set (make-local-variable 'gnus-undo-actions) nil)
 111   (set (make-local-variable 'gnus-undo-boundary) t)
 112   (when gnus-undo-mode
 113     ;; Set up the menu.
 114     (when (gnus-visual-p 'undo-menu 'menu)
 115       (gnus-undo-make-menu-bar))
 116     (gnus-add-minor-mode 'gnus-undo-mode "" gnus-undo-mode-map)
 117     (make-local-hook 'post-command-hook)
 118     (add-hook 'post-command-hook 'gnus-undo-boundary nil t)
 119     (gnus-run-hooks 'gnus-undo-mode-hook)))
 120
 121 ;;; Interface functions.
 122
 123 (defun gnus-disable-undo (&optional buffer)
 124   "Disable undoing in the current buffer."
 125   (interactive)
 126   (save-excursion
 127     (when buffer
 128       (set-buffer buffer))
 129     (gnus-undo-mode -1)))
 130
 131 (defun gnus-undo-boundary ()
 132   "Set Gnus undo boundary."
 133   (if gnus-undo-boundary-inhibit
 134       (setq gnus-undo-boundary-inhibit nil)
 135     (setq gnus-undo-boundary t)))
 136
 137 (defun gnus-undo-force-boundary ()
 138   "Set Gnus undo boundary."
 139   (setq gnus-undo-boundary-inhibit nil
 140         gnus-undo-boundary t))
 141
 142 (defun gnus-undo-register (form)
 143   "Register FORMS as something to be performed to undo a change.
 144 FORMS may use backtick quote syntax."
 145   (when gnus-undo-mode
 146     (gnus-undo-register-1
 147      `(lambda ()
 148         ,form))))
 149
 150 (put 'gnus-undo-register 'lisp-indent-function 0)
 151 (put 'gnus-undo-register 'edebug-form-spec '(body))
 152
 153 (defun gnus-undo-register-1 (function)
 154   "Register FUNCTION as something to be performed to undo a change."
 155   (when gnus-undo-mode
 156     (cond
 157      ;; We are on a boundary, so we create a new action.
 158      (gnus-undo-boundary
 159       (push (list function) gnus-undo-actions)
 160       (setq gnus-undo-boundary nil))
 161      ;; Prepend the function to an old action.
 162      (gnus-undo-actions
 163       (setcar gnus-undo-actions (cons function (car gnus-undo-actions))))
 164      ;; Initialize list.
 165      (t
 166       (setq gnus-undo-actions (list (list function)))))
 167     ;; Limit the length of the undo list.
 168     (let ((next (nthcdr gnus-undo-limit gnus-undo-actions)))
 169       (when next
 170         (setcdr next nil)))
 171     ;; We are not at a boundary...
 172     (setq gnus-undo-boundary-inhibit t)))
 173
 174 (defun gnus-undo (n)
 175   "Undo some previous changes in Gnus buffers.
 176 Repeat this command to undo more changes.
 177 A numeric argument serves as a repeat count."
 178   (interactive "p")
 179   (unless gnus-undo-mode
 180     (error "Undoing is not enabled in this buffer"))
 181   (message "%s" last-command)
 182   (when (or (not (eq last-command 'gnus-undo))
 183             (not gnus-undo-last))
 184     (setq gnus-undo-last gnus-undo-actions))
 185   (let ((action (pop gnus-undo-last)))
 186     (unless action
 187       (error "Nothing further to undo"))
 188     (setq gnus-undo-actions (delq action gnus-undo-actions))
 189     (setq gnus-undo-boundary t)
 190     (while action
 191       (funcall (pop action)))))
 192
 193 (provide 'gnus-undo)
 194
 195 ;;; gnus-undo.el ends here