path: root/lisp/autorevert.el

;;; autorevert.el --- revert buffers when files on disk change

;; Copyright (C) 1997, 1998, 1999, 2001 Free Software Foundation, Inc.

;; Author: Anders Lindgren <andersl@andersl.com>
;; Keywords: convenience
;; Created: 1997-06-01
;; Date: 1999-11-30

;; 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 has 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 revert 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 operate by checking the time stamp of all files at
;; intervals of `auto-revert-interval'.  The default is every five
;; seconds.  The check is aborted whenever the user actually uses
;; Emacs.  You should never even notice that this package is active
;; (except that your buffers will be reverted, of course).

;; 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
;; customise the option `global-auto-revert-mode' or 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 buffers when files on disk change.

Auto-Revert Mode can be activated for individual buffer.
Global Auto-Revert Mode applies to all buffers."
  :group 'files
  :group 'convenience)


;; Variables:

;; Autoload for the benefit of `make-mode-line-mouse-sensitive'.
;;;###autoload
(defvar auto-revert-mode nil
  "*Non-nil when Auto-Revert Mode is active.
Never set this variable directly, use the command `auto-revert-mode' instead.")
(put 'auto-revert-mode 'permanent-local t)

(defvar auto-revert-timer nil
  "Timer used by Auto-Revert Mode.")

(defcustom auto-revert-interval 5
  "Time, in seconds, between Auto-Revert Mode file checks.
The value may be an integer or floating point number.

If a timer is already active, there are two ways to make sure
that the new value will take effect immediately.  You can set
this variable through Custom or you can call the command
`auto-revert-set-timer' after setting the variable.  Otherwise,
the new value will take effect the first time Auto Revert Mode
calls `auto-revert-set-timer' for internal reasons or in your
next editing session."
  :group 'auto-revert
  :type 'number
  :set (lambda (variable value)
	 (set-default variable value)
	 (and (boundp 'auto-revert-timer)
	      auto-revert-timer
	      (auto-revert-set-timer))))

(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.
When non-nil, a message is generated 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 over time, or between buffers.  Hence 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' and a `buffer-stale-function' are
reverted by Global Auto-Revert Mode.

Use this option with care since it could lead to excessive reverts.
Note also that for some non-file buffers the check whether the
buffer needs updating may be imperfect, due to efficiency
considerations, and may not take all information listed in the
buffer into account.  Hence, a non-nil value for this option does
not necessarily make manual updates useless for non-file buffers."
  :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)

(defcustom auto-revert-check-vc-info nil
  "If non-nil Auto Revert Mode reliably updates version control info.
Auto Revert Mode updates version control info whenever the buffer
needs reverting, regardless of the value of this variable.
However, the version control state can change without changes to
the work file.  If the change is made from the current Emacs
session, all info is updated.  But if, for instance, a new
version is checked in from outside the current Emacs session, the
version control number in the mode line, as well as other version
control related information, may not be properly updated.  If you
are worried about this, set this variable to a non-nil value.

This currently works by automatically updating the version
control info every `auto-revert-interval' seconds.  Nevertheless,
it should not cause excessive CPU usage on a reasonably fast
machine, if it does not apply to too many version controlled
buffers.  CPU usage depends on the version control system"
  :group 'auto-revert
  :type 'boolean
  :version "21.4")

(defvar global-auto-revert-ignore-buffer nil
  "*When non-nil, Global Auto-Revert Mode will not revert this buffer.

This variable becomes buffer local when set in any fashion.")
(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-remaining-buffers '()
  "Buffers not checked when user input stopped execution.")


;; Functions:

;;;###autoload
(define-minor-mode auto-revert-mode
  "Toggle reverting buffer when file on disk changes.

With arg, turn Auto Revert mode on if and only if arg is positive.
This is a minor mode that affects only the current buffer.
Use `global-auto-revert-mode' to automatically revert all buffers."
  nil auto-revert-mode-text nil
  (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)))


;;;###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
(define-minor-mode global-auto-revert-mode
  "Revert any buffer when file on disk changes.

With arg, turn Auto Revert mode on globally if and only if arg is positive.
This is a minor mode that affects all buffers.
Use `auto-revert-mode' to revert a particular buffer."
  :global t :group 'auto-revert :lighter global-auto-revert-mode-text
  (auto-revert-set-timer)
  (when global-auto-revert-mode
    (auto-revert-buffers)))


(defun auto-revert-set-timer ()
  "Restart or cancel the timer used by Auto-Revert Mode.
If such a timer is active, cancel it.  Start a new timer if
Global Auto-Revert Mode is active or if Auto-Revert Mode is active
in some buffer.  Restarting the timer ensures that Auto-Revert Mode
will use an up-to-date value of `auto-revert-interval'"
  (interactive)
  (if (timerp auto-revert-timer)
      (cancel-timer auto-revert-timer))
  (setq auto-revert-timer
	(if (or global-auto-revert-mode auto-revert-buffer-list)
	    (run-with-timer auto-revert-interval
			    auto-revert-interval
			    'auto-revert-buffers)
	  nil)))

(defun auto-revert-active-p ()
  "Check if auto-revert is active (in current buffer or globally)."
  (or auto-revert-mode
      (and
       global-auto-revert-mode
       (not global-auto-revert-ignore-buffer)
       (not (memq major-mode
		  global-auto-revert-ignore-modes)))))

(defun auto-revert-handler ()
  "Revert current buffer, if appropriate.
This is an internal function used by Auto-Revert Mode."
  (unless (buffer-modified-p)
    (let (revert)
      (or (and (buffer-file-name)
	       (file-readable-p (buffer-file-name))
	       (not (verify-visited-file-modtime (current-buffer)))
	       (setq revert t))
	  (and (or auto-revert-mode global-auto-revert-non-file-buffers)
	       revert-buffer-function
	       (boundp 'buffer-stale-function)
	       (functionp buffer-stale-function)
	       (setq revert (funcall buffer-stale-function t))))
      (when revert
	(when (and auto-revert-verbose
		   (not (eq revert 'fast)))
	  (message "Reverting buffer `%s'." (buffer-name)))
	(revert-buffer 'ignore-auto 'dont-ask 'preserve-modes))
      ;; `preserve-modes' avoids changing the (minor) modes.  But we
      ;; do want to reset the mode for VC, so we do it manually.
      (when (or revert auto-revert-check-vc-info)
	(vc-find-file-hook)))))

(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' and
a `buffer-stale-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 there is user input.  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 responsible 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?
	    (with-current-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 (auto-revert-active-p) (auto-revert-handler)))
	  ;; 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:
(provide 'autorevert)

(run-hooks 'auto-revert-load-hook)

;;; arch-tag: f6bcb07b-4841-477e-9e44-b18678e58876
;;; autorevert.el ends here