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