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1 ;;; userlock.el --- handle file access contention between multiple users
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2
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3 ;; Copyright (C) 1985, 1986, 1993 Free Software Foundation, inc.
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4
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5 ;; Maintainer: FSF
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6 ;; Keywords: internal
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7
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8 ;; This file is part of XEmacs.
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9
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10 ;; XEmacs is free software; you can redistribute it and/or modify it
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11 ;; under the terms of the GNU General Public License as published by
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12 ;; the Free Software Foundation; either version 2, or (at your option)
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13 ;; any later version.
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14
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15 ;; XEmacs is distributed in the hope that it will be useful, but
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16 ;; WITHOUT ANY WARRANTY; without even the implied warranty of
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17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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18 ;; General Public License for more details.
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19
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20 ;; You should have received a copy of the GNU General Public License
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70
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21 ;; along with XEmacs; see the file COPYING. If not, write to the
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22 ;; Free Software Foundation, 59 Temple Place - Suite 330,
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23 ;; Boston, MA 02111-1307, USA.
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24
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70
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25 ;;; Synched up with: FSF 19.30.
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26
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27 ;;; Commentary:
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28
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29 ;; This file is autoloaded to handle certain conditions
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30 ;; detected by the file-locking code within XEmacs.
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31 ;; The two entry points are `ask-user-about-lock' and
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32 ;; `ask-user-about-supersession-threat'.
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33
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34 ;;; Code:
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35
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70
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36 (define-error 'file-locked "File is locked" 'file-error)
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37
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38 (defun ask-user-about-lock-minibuf (fn opponent)
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39 (save-window-excursion
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40 (let (answer)
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41 (while (null answer)
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42 (message "%s is locking %s: action (s, q, p, ?)? " opponent fn)
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43 (let ((tem (let ((inhibit-quit t)
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44 (cursor-in-echo-area t))
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45 (prog1 (downcase (read-char))
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46 (setq quit-flag nil)))))
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47 (if (= tem help-char)
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48 (ask-user-about-lock-help)
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49 (setq answer (assoc tem '((?s . t)
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50 (?q . yield)
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51 (?\C-g . yield)
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52 (?p . nil)
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53 (?? . help))))
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54 (cond ((null answer)
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55 (beep)
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56 (message "Please type q, s, or p; or ? for help")
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57 (sit-for 3))
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58 ((eq (cdr answer) 'help)
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59 (ask-user-about-lock-help)
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60 (setq answer nil))
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61 ((eq (cdr answer) 'yield)
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62 (signal 'file-locked (list fn opponent)))))))
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63 (cdr answer))))
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64
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65 (defun ask-user-about-lock-help ()
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66 (with-output-to-temp-buffer "*Help*"
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67 (princ "It has been detected that you want to modify a file that someone else has
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68 already started modifying in EMACS.
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69
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70 You can <s>teal the file; The other user becomes the
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71 intruder if (s)he ever unmodifies the file and then changes it again.
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72 You can <p>roceed; you edit at your own (and the other user's) risk.
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73 You can <q>uit; don't modify this file.")
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74 (save-excursion
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75 (set-buffer standard-output)
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76 (help-mode))))
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77
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70
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78 (define-error 'file-supersession "File changed on disk" 'file-error)
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79
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80 (defun ask-user-about-supersession-threat-minibuf (fn)
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81 (save-window-excursion
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82 (let (answer)
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83 (while (null answer)
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84 (message "%s changed on disk; really edit the buffer? (y, n or C-h) "
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85 (file-name-nondirectory fn))
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86 (let ((tem (downcase (let ((cursor-in-echo-area t))
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87 (read-char)))))
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88 (setq answer
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89 (if (= tem help-char)
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90 'help
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91 (cdr (assoc tem '((?n . yield)
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92 (?\C-g . yield)
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93 (?y . proceed)
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94 (?? . help))))))
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95 (cond ((null answer)
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96 (beep)
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97 (message "Please type y or n; or ? for help")
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98 (sit-for 3))
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99 ((eq answer 'help)
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100 (ask-user-about-supersession-help)
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101 (setq answer nil))
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102 ((eq answer 'yield)
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103 (signal 'file-supersession
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104 (list fn))))))
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105 (message
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106 "File on disk now will become a backup file if you save these changes.")
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107 (setq buffer-backed-up nil))))
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108
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109 (defun ask-user-about-supersession-help ()
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110 (with-output-to-temp-buffer "*Help*"
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111 (princ "You want to modify a buffer whose disk file has changed
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112 since you last read it in or saved it with this buffer.
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113
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114 If you say `y' to go ahead and modify this buffer,
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115 you risk ruining the work of whoever rewrote the file.
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116 If you say `n', the change you started to make will be aborted.
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117
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118 Usually, you should type `n' and then `M-x revert-buffer',
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119 to get the latest version of the file, then make the change again.")
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120 (save-excursion
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121 (set-buffer standard-output)
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122 (help-mode))))
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123
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124
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125 ;;; dialog-box versions
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126
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127 (defun ask-user-about-lock-dbox (fn opponent)
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128 (let ((echo-keystrokes 0)
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129 (dbox
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130 (cons
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131 (format "%s is locking %s\n
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132 It has been detected that you want to modify a file that
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133 someone else has already started modifying in XEmacs."
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134 opponent fn)
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135 '(["Steal Lock\n\nThe other user will\nbecome the intruder" steal t]
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136 ["Proceed\n\nEdit file at your own\n\(and the other user's) risk"
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137 proceed t]
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138 nil
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139 ["Abort\n\nDon't modify the buffer\n" yield t]))))
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140 (popup-dialog-box dbox)
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141 (catch 'aual-done
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142 (while t
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143 (let ((event (next-command-event)))
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144 (cond ((and (misc-user-event-p event) (eq (event-object event) 'proceed))
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145 (throw 'aual-done nil))
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146 ((and (misc-user-event-p event) (eq (event-object event) 'steal))
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147 (throw 'aual-done t))
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148 ((and (misc-user-event-p event) (eq (event-object event) 'yield))
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149 (signal 'file-locked (list fn opponent)))
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150 ((button-release-event-p event) ;; don't beep twice
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151 nil)
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152 (t
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153 (beep)
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154 (message "please answer the dialog box"))))))))
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155
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156 (defun ask-user-about-supersession-threat-dbox (fn)
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157 (let ((echo-keystrokes 0)
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158 (dbox
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159 (cons
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160 (format "File %s has changed on disk
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161 since its buffer was last read in or saved.
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162
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163 Do you really want to edit the buffer? " fn)
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164 '(["Yes\n\nEdit the buffer anyway,\nignoring the disk file"
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165 proceed t]
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166 ["No\n\nDon't modify the buffer\n" yield t]
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167 nil
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168 ["No\n\nDon't modify the buffer\nbut revert it" revert t]
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169 ))))
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170 (popup-dialog-box dbox)
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171 (catch 'auast-done
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172 (while t
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173 (let ((event (next-command-event)))
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174 (cond ((and (misc-user-event-p event) (eq (event-object event) 'proceed))
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175 (throw 'auast-done nil))
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176 ((and (misc-user-event-p event) (eq (event-object event) 'yield))
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177 (signal 'file-supersession (list fn)))
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178 ((and (misc-user-event-p event) (eq (event-object event) 'revert))
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179 (or (equal fn (buffer-file-name))
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180 (error
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181 "ask-user-about-supersession-threat called bogusly"))
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182 (revert-buffer nil t)
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183 (signal 'file-supersession
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184 (list fn "(reverted)")))
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185 ((button-release-event-p event) ;; don't beep twice
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186 nil)
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187 (t
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188 (beep)
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189 (message "please answer the dialog box"))))))))
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190
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191
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192 ;;; top-level
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193
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194 ;;;###autoload
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195 (defun ask-user-about-lock (fn opponent)
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196 "Ask user what to do when he wants to edit FILE but it is locked by USER.
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197 This function has a choice of three things to do:
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198 do (signal 'file-locked (list FILE USER))
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199 to refrain from editing the file
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200 return t (grab the lock on the file)
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201 return nil (edit the file even though it is locked).
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202 You can rewrite it to use any criterion you like to choose which one to do."
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203 (discard-input)
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204 (if (and (fboundp 'popup-dialog-box)
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205 (or (button-press-event-p last-command-event)
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206 (button-release-event-p last-command-event)
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207 (misc-user-event-p last-command-event)))
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208 (ask-user-about-lock-dbox fn opponent)
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209 (ask-user-about-lock-minibuf fn opponent)))
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210
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211 ;;;###autoload
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212 (defun ask-user-about-supersession-threat (fn)
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213 "Ask a user who is about to modify an obsolete buffer what to do.
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214 This function has two choices: it can return, in which case the modification
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215 of the buffer will proceed, or it can (signal 'file-supersession (file)),
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216 in which case the proposed buffer modification will not be made.
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217
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218 You can rewrite this to use any criterion you like to choose which one to do.
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219 The buffer in question is current when this function is called."
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220 (discard-input)
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221 (if (and (fboundp 'popup-dialog-box)
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222 (or (button-press-event-p last-command-event)
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223 (button-release-event-p last-command-event)
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224 (misc-user-event-p last-command-event)))
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225 (ask-user-about-supersession-threat-dbox fn)
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226 (ask-user-about-supersession-threat-minibuf fn)))
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227
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228 ;;; userlock.el ends here
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