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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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21 ;; along with XEmacs; see the file COPYING. If not, write to the Free
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22 ;; Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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23
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24 ;;; Synched up with: FSF 19.30.
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25
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26 ;;; Commentary:
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27
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28 ;; This file is autoloaded to handle certain conditions
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29 ;; detected by the file-locking code within XEmacs.
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30 ;; The two entry points are `ask-user-about-lock' and
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31 ;; `ask-user-about-supersession-threat'.
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32
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33 ;;; Code:
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34
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35 (define-error 'file-locked "File is locked" 'file-error)
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36
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37 (defun ask-user-about-lock-minibuf (fn opponent)
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38 (save-window-excursion
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39 (let (answer)
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40 (while (null answer)
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41 (message "%s is locking %s: action (s, q, p, ?)? " opponent fn)
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42 (let ((tem (let ((inhibit-quit t)
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43 (cursor-in-echo-area t))
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44 (prog1 (downcase (read-char))
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45 (setq quit-flag nil)))))
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46 (if (= tem help-char)
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47 (ask-user-about-lock-help)
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48 (setq answer (assoc tem '((?s . t)
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49 (?q . yield)
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50 (?\C-g . yield)
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51 (?p . nil)
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52 (?? . help))))
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53 (cond ((null answer)
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54 (beep)
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55 (message "Please type q, s, or p; or ? for help")
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56 (sit-for 3))
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57 ((eq (cdr answer) 'help)
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58 (ask-user-about-lock-help)
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59 (setq answer nil))
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60 ((eq (cdr answer) 'yield)
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61 (signal 'file-locked (list fn opponent)))))))
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62 (cdr answer))))
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63
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64 (defun ask-user-about-lock-help ()
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65 (with-output-to-temp-buffer "*Help*"
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66 (princ "It has been detected that you want to modify a file that someone else has
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67 already started modifying in EMACS.
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68
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69 You can <s>teal the file; The other user becomes the
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70 intruder if (s)he ever unmodifies the file and then changes it again.
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71 You can <p>roceed; you edit at your own (and the other user's) risk.
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72 You can <q>uit; don't modify this file.")
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73 (save-excursion
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74 (set-buffer standard-output)
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75 (help-mode))))
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76
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77 (define-error 'file-supersession "File changed on disk" 'file-error)
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78
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79 (defun ask-user-about-supersession-threat-minibuf (fn)
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80 (save-window-excursion
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81 (let (answer)
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82 (while (null answer)
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83 (message "%s changed on disk; really edit the buffer? (y, n or C-h) "
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84 (file-name-nondirectory fn))
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85 (let ((tem (downcase (let ((cursor-in-echo-area t))
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86 (read-char)))))
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87 (setq answer
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88 (if (= tem help-char)
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89 'help
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90 (cdr (assoc tem '((?n . yield)
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91 (?\C-g . yield)
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92 (?y . proceed)
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93 (?? . help))))))
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94 (cond ((null answer)
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95 (beep)
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96 (message "Please type y or n; or ? for help")
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97 (sit-for 3))
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98 ((eq answer 'help)
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99 (ask-user-about-supersession-help)
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100 (setq answer nil))
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101 ((eq answer 'yield)
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102 (signal 'file-supersession
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103 (list fn))))))
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104 (message
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105 "File on disk now will become a backup file if you save these changes.")
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106 (setq buffer-backed-up nil))))
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107
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108 (defun ask-user-about-supersession-help ()
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109 (with-output-to-temp-buffer "*Help*"
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110 (princ "You want to modify a buffer whose disk file has changed
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111 since you last read it in or saved it with this buffer.
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112
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113 If you say `y' to go ahead and modify this buffer,
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114 you risk ruining the work of whoever rewrote the file.
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115 If you say `n', the change you started to make will be aborted.
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116
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117 Usually, you should type `n' and then `M-x revert-buffer',
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118 to get the latest version of the file, then make the change again.")
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119 (save-excursion
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120 (set-buffer standard-output)
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121 (help-mode))))
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122
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123
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124 ;;; dialog-box versions
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125
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126 (defun ask-user-about-lock-dbox (fn opponent)
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127 (let ((echo-keystrokes 0)
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128 (dbox
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129 (cons
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130 (format "%s is locking %s\n
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131 It has been detected that you want to modify a file that
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132 someone else has already started modifying in XEmacs."
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133 opponent fn)
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134 '(["Steal Lock\n\nThe other user will\nbecome the intruder" steal t]
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135 ["Proceed\n\nEdit file at your own\n\(and the other user's) risk"
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136 proceed t]
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137 nil
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138 ["Abort\n\nDon't modify the buffer\n" yield t]))))
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139 (popup-dialog-box dbox)
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140 (catch 'aual-done
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141 (while t
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142 (let ((event (next-command-event)))
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143 (cond ((and (misc-user-event-p event) (eq (event-object event) 'proceed))
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144 (throw 'aual-done nil))
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145 ((and (misc-user-event-p event) (eq (event-object event) 'steal))
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146 (throw 'aual-done t))
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147 ((and (misc-user-event-p event) (eq (event-object event) 'yield))
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148 (signal 'file-locked (list fn opponent)))
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149 ((button-release-event-p event) ;; don't beep twice
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150 nil)
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151 (t
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152 (beep)
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153 (message "please answer the dialog box"))))))))
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154
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155 (defun ask-user-about-supersession-threat-dbox (fn)
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156 (let ((echo-keystrokes 0)
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157 (dbox
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158 (cons
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159 (format "File %s has changed on disk
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160 since its buffer was last read in or saved.
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161
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162 Do you really want to edit the buffer? " fn)
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163 '(["Yes\n\nEdit the buffer anyway,\nignoring the disk file"
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164 proceed t]
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165 ["No\n\nDon't modify the buffer\n" yield t]
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166 nil
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167 ["No\n\nDon't modify the buffer\nbut revert it" revert t]
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168 ))))
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169 (popup-dialog-box dbox)
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170 (catch 'auast-done
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171 (while t
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172 (let ((event (next-command-event)))
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173 (cond ((and (misc-user-event-p event) (eq (event-object event) 'proceed))
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174 (throw 'auast-done nil))
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175 ((and (misc-user-event-p event) (eq (event-object event) 'yield))
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176 (signal 'file-supersession (list fn)))
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177 ((and (misc-user-event-p event) (eq (event-object event) 'revert))
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178 (or (equal fn (buffer-file-name))
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179 (error
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180 "ask-user-about-supersession-threat called bogusly"))
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181 (revert-buffer nil t)
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182 (signal 'file-supersession
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183 (list fn "(reverted)")))
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184 ((button-release-event-p event) ;; don't beep twice
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185 nil)
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186 (t
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187 (beep)
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188 (message "please answer the dialog box"))))))))
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189
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190
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191 ;;; top-level
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192
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193 ;;;###autoload
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194 (defun ask-user-about-lock (fn opponent)
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195 "Ask user what to do when he wants to edit FILE but it is locked by USER.
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196 This function has a choice of three things to do:
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197 do (signal 'file-locked (list FILE USER))
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198 to refrain from editing the file
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199 return t (grab the lock on the file)
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200 return nil (edit the file even though it is locked).
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201 You can rewrite it to use any criterion you like to choose which one to do."
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202 (discard-input)
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203 (if (and (fboundp 'popup-dialog-box)
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204 (or (button-press-event-p last-command-event)
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205 (button-release-event-p last-command-event)
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206 (misc-user-event-p last-command-event)))
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207 (ask-user-about-lock-dbox fn opponent)
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208 (ask-user-about-lock-minibuf fn opponent)))
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209
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210 ;;;###autoload
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211 (defun ask-user-about-supersession-threat (fn)
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212 "Ask a user who is about to modify an obsolete buffer what to do.
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213 This function has two choices: it can return, in which case the modification
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214 of the buffer will proceed, or it can (signal 'file-supersession (file)),
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215 in which case the proposed buffer modification will not be made.
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216
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217 You can rewrite this to use any criterion you like to choose which one to do.
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218 The buffer in question is current when this function is called."
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219 (discard-input)
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220 (if (and (fboundp 'popup-dialog-box)
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221 (or (button-press-event-p last-command-event)
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222 (button-release-event-p last-command-event)
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223 (misc-user-event-p last-command-event)))
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224 (ask-user-about-supersession-threat-dbox fn)
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225 (ask-user-about-supersession-threat-minibuf fn)))
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226
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227 ;;; userlock.el ends here
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