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+;; autorevert --- Revert buffers when file on disk change.
+
+;; Copyright (C) 1997 Free Software Foundation, Inc.
+
+;; Author: Anders Lindgren <andersl@csd.uu.se>
+;; Created: 1 Jun 1997
+;; Date: 3 Jul 1997
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 2, or (at your option)
+;; any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs; see the file COPYING.  If not, write to the
+;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+;; Boston, MA 02111-1307, USA.
+
+;;; Commentary:
+
+;; Introduction:
+;;
+;; Whenever a file that Emacs is editing has been changed by another
+;; program the user normally have to execute the command `revert-buffer'
+;; to load the new content of the file into Emacs.
+;;
+;; This package contains two minor modes: Global Auto-Revert Mode and
+;; Auto-Revert Mode.  Both modes automatically reverts buffers
+;; whenever the corresponding files have been changed on disk.
+;;
+;; Auto-Revert Mode can be activated for individual buffers.
+;; Global Auto-Revert Mode applies to all file buffers.
+;;
+;; Both modes operates by checking the time stamp of all files at
+;; given intervals, the default is every five seconds.  The check is
+;; aborted whenever the user actually use Emacs.  Hopefully you will
+;; never even notice that this package is active (except that your
+;; buffers will be reverted, of course).
+
+;; Installation:
+;;
+;; To install this package, place it in somewhere on Emacs' load-path,
+;; byte-compile it (not necessary), and place the following lines in
+;; the appropriate init file:
+;;
+;; (autoload 'auto-revert-mode "autorevert" nil t)
+;; (autoload 'turn-on-auto-revert-mode "autorevert" nil nil)
+;; (autoload 'global-auto-revert-mode "autorevert" nil t)
+
+;; Usage:
+;;
+;; Go to the appropriate buffer and press:
+;;   M-x auto-revert-mode RET
+;;
+;; To activate Global Auto-Revert Mode, press:
+;;   M-x global-auto-revert-mode RET
+;;
+;; To activate Global Auto-Revert Mode every time Emacs is started the
+;; following line could be added to your ~/.emacs:
+;;   (global-auto-revert-mode 1)
+;;
+;; The function `turn-on-auto-revert-mode' could be added to any major
+;; mode hook to activate Auto-Revert Mode for all buffers in that
+;; mode.  For example, the following line will activate Auto-Revert
+;; Mode in all C mode buffers:
+;;
+;; (add-hook 'c-mode-hook 'turn-on-auto-revert-mode)
+
+;;; Code:
+
+;; Dependencies:
+
+(require 'timer)
+(eval-when-compile (require 'cl))
+
+
+;; Custom Group:
+;;
+;; The two modes will be placed next to Auto Save Mode under the
+;; Files group under Emacs.
+
+(defgroup auto-revert nil
+  "Revert individual buffer when file on disk change.
+
+Auto-Revert Mode can be activated for individual buffer.
+Global Auto-Revert Mode applies to all buffers."
+  :group 'files)
+
+
+;; Variables:
+
+(defvar auto-revert-mode nil
+  "*Non-nil when Auto-Revert Mode is active.
+
+Do never set this variable directly, use the command
+`auto-revert-mode' instead.")
+
+(defcustom global-auto-revert-mode nil
+  "When on, buffers are automatically reverted when files on disk change.
+
+Set this variable when using \\[customize] only.  Otherwise, use the
+command `global-auto-revert-mode' instead."
+  :group 'auto-revert
+  :initialize 'custom-initialize-default
+  :set '(lambda (symbol value)
+          (global-auto-revert-mode (or value 0)))
+  :type 'boolean
+  :require 'autorevert)
+
+(defcustom auto-revert-interval 5
+  "Time, in seconds, between Auto-Revert Mode file checks."
+  :group 'auto-revert
+  :type 'integer)
+
+(defcustom auto-revert-stop-on-user-input t
+  "When non-nil Auto-Revert Mode stops checking files on user input."
+  :group 'auto-revert
+  :type 'boolean)
+
+(defcustom auto-revert-verbose t
+  "When nil, Auto-Revert Mode will not generate any messages.
+
+Currently, messages are generated when the mode is activated or
+deactivated, and whenever a file is reverted."
+  :group 'auto-revert
+  :type 'boolean)
+
+(defcustom auto-revert-mode-text " ARev"
+  "String to display in the mode line when Auto-Revert Mode is active.
+
+\(When the string is not empty, make sure that it has a leading space.)"
+  :tag "Auto Revert Mode Text"          ; To separate it from `global-...'
+  :group 'auto-revert
+  :type 'string)
+
+(defcustom auto-revert-mode-hook nil
+  "Functions to run when Auto-Revert Mode is activated."
+  :tag "Auto Revert Mode Hook"          ; To separate it from `global-...'
+  :group 'auto-revert
+  :type 'hook)
+
+(defcustom global-auto-revert-mode-text ""
+  "String to display when Global Auto-Revert Mode is active.
+
+The default is nothing since when this mode is active this text doesn't
+vary neither over time, nor between buffers.  Hence a mode line text
+would only waste precious space."
+  :group 'auto-revert
+  :type 'string)
+
+(defcustom global-auto-revert-mode-hook nil
+  "Hook called when Global Auto-Revert Mode is activated."
+  :group 'auto-revert
+  :type 'hook)
+
+(defcustom global-auto-revert-non-file-buffers nil
+  "*When nil only file buffers are reverted by Global Auto-Revert Mode.
+
+When non-nil, both file buffers and buffers with a custom
+`revert-buffer-function' are reverted by Global Auto-Revert Mode."
+  :group 'auto-revert
+  :type 'boolean)
+
+(defcustom global-auto-revert-non-file-buffers nil
+  "When nil only file buffers are reverted by Global Auto-Revert Mode.
+
+When non-nil, both file buffers and buffers with a custom
+`revert-buffer-function' are reverted by Global Auto-Revert Mode.
+
+Use this option with care since it could lead to excessive reverts."
+  :group 'auto-revert
+  :type 'boolean)
+
+(defcustom global-auto-revert-ignore-modes '()
+  "List of major modes Global Auto-Revert Mode should not check."
+  :group 'auto-revert
+  :type '(repeat sexp))
+
+(defcustom auto-revert-load-hook nil
+  "Functions to run when Auto-Revert Mode is first loaded."
+  :tag "Load Hook"
+  :group 'auto-revert
+  :type 'hook)
+
+(defvar global-auto-revert-ignore-buffer nil
+  "*When non-nil, Gobal Auto-Revert Mode will not revert this buffer.
+
+This variable becomes buffer local when set in any faishon.")
+(make-variable-buffer-local 'global-auto-revert-ignore-buffer)
+
+
+;; Internal variables:
+
+(defvar auto-revert-buffer-list '()
+  "List of buffers in Auto-Revert Mode.
+
+Note that only Auto-Revert Mode, never Global Auto-Revert Mode, adds
+buffers to this list.
+
+The timer function `auto-revert-buffers' is responsible for purging
+the list of old buffers.")
+
+(defvar auto-revert-timer nil
+  "Timer used by Auto-Revert Mode.")
+
+(defvar auto-revert-remaining-buffers '()
+  "Buffers not checked when user input stopped execution.")
+
+
+;; Functions:
+
+;;;###autoload
+(defun auto-revert-mode (&optional arg)
+  "Revert buffer when file on disk change.
+
+This is a minor mode that affect only the current buffer.
+Use `global-auto-revert-mode' to automatically revert all buffers."
+  (interactive "P")
+  (make-local-variable 'auto-revert-mode)
+  (setq auto-revert-mode
+        (if (null arg)
+            (not auto-revert-mode)
+          (> (prefix-numeric-value arg) 0)))
+  (if (and auto-revert-verbose
+           (interactive-p))
+      (message "Auto-Revert Mode is now %s."
+               (if auto-revert-mode "on" "off")))
+  (if auto-revert-mode
+      (if (not (memq (current-buffer) auto-revert-buffer-list))
+          (push (current-buffer) auto-revert-buffer-list))
+    (setq auto-revert-buffer-list
+          (delq (current-buffer) auto-revert-buffer-list)))
+  (auto-revert-set-timer)
+  (when auto-revert-mode
+    (auto-revert-buffers)
+    (run-hooks 'auto-revert-mode-hook)))
+
+
+;;;###autoload
+(defun turn-on-auto-revert-mode ()
+  "Turn on Auto-Revert Mode.
+
+This function is designed to be added to hooks, for example:
+  (add-hook 'c-mode-hook 'turn-on-auto-revert-mode)"
+  (auto-revert-mode 1))
+
+
+;;;###autoload
+(defun global-auto-revert-mode (&optional arg)
+  "Revert any buffer when file on disk change.
+
+This is a minor mode that affect all buffers.
+Use `auto-revert-mode' to revert a particular buffer."
+  (interactive "P")
+  (setq global-auto-revert-mode
+        (if (null arg)
+            (not global-auto-revert-mode)
+          (> (prefix-numeric-value arg) 0)))
+  (if (and auto-revert-verbose
+           (interactive-p))
+      (message "Gobal Auto-Revert Mode is now %s."
+               (if global-auto-revert-mode "on" "off")))
+  (auto-revert-set-timer)
+  (when global-auto-revert-mode
+    (auto-revert-buffers)      
+    (run-hooks 'global-auto-revert-mode-hook)))
+
+
+(defun auto-revert-set-timer ()
+  "Restart or cancel the timer."
+  (if (timerp auto-revert-timer)
+      (cancel-timer auto-revert-timer))
+  (if (or global-auto-revert-mode auto-revert-buffer-list)
+      (setq auto-revert-timer (run-with-timer auto-revert-interval
+                                              auto-revert-interval
+                                              'auto-revert-buffers))
+    (setq auto-revert-timer nil)))
+
+
+(defun auto-revert-buffers ()
+  "Revert buffers as specified by Auto-Revert and Global Auto-Revert Mode.
+
+Should `global-auto-revert-mode' be active all file buffers are checked.
+
+Should `auto-revert-mode' be active in some buffers, those buffers
+are checked.
+
+Non-file buffers that have a custom `revert-buffer-function' are
+reverted either when Auto-Revert Mode is active in that buffer, or
+when the variable `global-auto-revert-non-file-buffers' is non-nil
+and Global Auto-Revert Mode is active.
+
+This function stops whenever the user use Emacs.  The buffers not
+checked are stored in the variable `auto-revert-remaining-buffers'.
+
+To avoid starvation, the buffers in `auto-revert-remaining-buffers'
+are checked first the next time this function is called.
+
+This function is also responslible for removing buffers no longer in
+Auto-Revert mode from `auto-revert-buffer-list', and for canceling
+the timer when no buffers need to be checked."
+  (let ((bufs (if global-auto-revert-mode
+                  (buffer-list)
+                auto-revert-buffer-list))
+        (remaining '())
+        (new '()))
+    ;; Partition `bufs' into two halves depending on whether or not
+    ;; the buffers are in `auto-revert-remaining-buffers'.  The two
+    ;; halves are then re-joined with the "remaining" buffers at the
+    ;; head of the list.
+    (dolist (buf auto-revert-remaining-buffers)
+      (if (memq buf bufs)
+          (push buf remaining)))
+    (dolist (buf bufs)
+      (if (not (memq buf remaining))
+          (push buf new)))
+    (setq bufs (nreverse (nconc new remaining)))
+    (while (and bufs
+                (not (and auto-revert-stop-on-user-input
+                          (input-pending-p))))
+      (let ((buf (car bufs)))
+        (if (buffer-name buf)           ; Buffer still alive?
+            (save-excursion
+              (set-buffer buf)
+              ;; Test if someone has turned off Auto-Revert Mode in a
+              ;; non-standard way, for example by changing major mode.
+              (if (and (not auto-revert-mode)
+                       (memq buf auto-revert-buffer-list))
+                  (setq auto-revert-buffer-list
+                        (delq buf auto-revert-buffer-list)))
+              (when (and
+                     (or auto-revert-mode
+                         (and
+                          global-auto-revert-mode
+                          (not global-auto-revert-ignore-buffer)
+                          (not (memq major-mode
+                                     global-auto-revert-ignore-modes))))
+                     (not (buffer-modified-p))
+                     (if (buffer-file-name)
+                         (and (file-readable-p (buffer-file-name))
+                              (not (verify-visited-file-modtime buf)))
+                       (and revert-buffer-function
+                            (or (and global-auto-revert-mode
+                                     global-auto-revert-non-file-buffers)
+                                auto-revert-mode))))
+                (if auto-revert-verbose
+                    (message "Reverting buffer `%s'." buf))
+                (revert-buffer t t)))
+          ;; Remove dead buffer from `auto-revert-buffer-list'.
+          (setq auto-revert-buffer-list
+                (delq buf auto-revert-buffer-list))))
+      (setq bufs (cdr bufs)))
+    (setq auto-revert-remaining-buffers bufs)
+    ;; Check if we should cancel the timer.
+    (when (and (not global-auto-revert-mode)
+               (null auto-revert-buffer-list))
+      (cancel-timer auto-revert-timer)
+      (setq auto-revert-timer nil))))
+
+
+;; The end:
+
+(unless (assq 'auto-revert-mode minor-mode-alist)
+  (push '(auto-revert-mode auto-revert-mode-text)
+        minor-mode-alist))
+(unless (assq 'global-auto-revert-mode minor-mode-alist)
+  (push '(global-auto-revert-mode global-auto-revert-mode-text)
+        minor-mode-alist))
+
+(provide 'autorevert)
+
+(run-hooks 'auto-revert-load-hook)
+
+;; This makes it possible to set Global Auto-Revert Mode from
+;; Customize.
+(if global-auto-revert-mode
+    (global-auto-revert-mode 1))
+
+;; autorevert.el ends here.