* lisp/desktop.el (desktop-auto-save-timeout): Change default to

`auto-save-timeout'.  Doc fix.
(desktop-save): Skip the timestamp in desktop-saved-frameset
when checking for auto-save changes.
(desktop-auto-save): Don't call desktop-auto-save-set-timer since
`desktop-auto-save' is called repeatedly by the idle timer.
(desktop-auto-save-set-timer): Replace `run-with-timer' with
`run-with-idle-timer' and a non-nil arg REPEAT.  Doc fix.

Fixes: debbugs:15331

3 files changed, 38 insertions, 17 deletions

diff --git a/etc/NEWS b/etc/NEWS
index ad385f4d373..0977accff3f 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -398,8 +398,8 @@ on the given date.
 
 ** Desktop
 
-*** `desktop-auto-save-timeout' defines the number of seconds between
-auto-saves of the desktop.
+*** `desktop-auto-save-timeout' defines the number of seconds idle time
+before auto-save of the desktop.
 
 *** `desktop-restore-frames', enabled by default, allows saving and
 restoring the frame/window configuration (frameset).  Additional options
diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 0cf8ed3da1e..1fe7bd62b04 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,5 +1,17 @@
 2013-12-16  Juri Linkov  <juri@jurta.org>
 
+        * desktop.el (desktop-auto-save-timeout): Change default to
+        `auto-save-timeout'.  Doc fix.
+        (desktop-save): Skip the timestamp in desktop-saved-frameset
+        when checking for auto-save changes.
+        (desktop-auto-save): Don't call desktop-auto-save-set-timer since
+        `desktop-auto-save' is called repeatedly by the idle timer.
+        (desktop-auto-save-set-timer): Replace `run-with-timer' with
+        `run-with-idle-timer' and a non-nil arg REPEAT.  Doc fix.
+        (Bug#15331)
+
+2013-12-16  Juri Linkov  <juri@jurta.org>
+
         * isearch.el (isearch-mode-map): Remove [escape] key bindinds.
         (Bug#16035)
         (isearch-pre-command-hook): Check `this-command' for symbolp.
diff --git a/lisp/desktop.el b/lisp/desktop.el
index cff78ba9da6..bdb16c00262 100644
--- a/lisp/desktop.el
+++ b/lisp/desktop.el
@@ -191,9 +191,9 @@ determine where the desktop is saved."
   :group 'desktop
   :version "22.1")
 
-(defcustom desktop-auto-save-timeout nil
-  "Number of seconds between auto-saves of the desktop.
-Zero or nil means disable timer-based auto-saving."
+(defcustom desktop-auto-save-timeout auto-save-timeout
+  "Number of seconds idle time before auto-save of the desktop.
+Zero or nil means disable auto-saving due to idleness."
   :type '(choice (const :tag "Off" nil)
                  (integer :tag "Seconds"))
   :set (lambda (symbol value)
@@ -992,12 +992,21 @@ and don't save the buffer if they are the same."
                 (insert ")\n\n"))))
 
           (setq default-directory desktop-dirname)
-          ;; If auto-saving, avoid writing if nothing has changed since the last write.
-          ;; Don't check 300 characters of the header that contains the timestamp.
-          (let ((checksum (and auto-save (md5 (current-buffer)
-                                              (+ (point-min) 300) (point-max)
-                                              'emacs-mule))))
-            (unless (and auto-save (equal checksum desktop-file-checksum))
+          ;; When auto-saving, avoid writing if nothing has changed since the last write.
+          (let* ((beg (and auto-save
+                           (save-excursion
+                             (goto-char (point-min))
+                             ;; Don't check the header with changing timestamp
+                             (and (search-forward "Global section" nil t)
+                                  ;; Also skip the timestamp in desktop-saved-frameset
+                                  ;; if it's saved in the first non-header line
+                                  (search-forward "desktop-saved-frameset"
+                                                  (line-beginning-position 3) t)
+                                  ;; This is saved after the timestamp
+                                  (search-forward (format "%S" desktop--app-id) nil t))
+                             (point))))
+                 (checksum (and beg (md5 (current-buffer) beg (point-max) 'emacs-mule))))
+            (unless (and checksum (equal checksum desktop-file-checksum))
               (let ((coding-system-for-write 'emacs-mule))
                 (write-region (point-min) (point-max) (desktop-full-file-name) nil 'nomessage))
               (setq desktop-file-checksum checksum)
@@ -1199,21 +1208,21 @@ Called by the timer created in `desktop-auto-save-set-timer'."
              ;; Save only to own desktop file.
              (eq (emacs-pid) (desktop-owner))
              desktop-dirname)
-    (desktop-save desktop-dirname nil t))
-  (desktop-auto-save-set-timer))
+    (desktop-save desktop-dirname nil t)))
 
 (defun desktop-auto-save-set-timer ()
-  "Reset the auto-save timer.
+  "Set the auto-save timer.
 Cancel any previous timer.  When `desktop-auto-save-timeout' is a positive
-integer, start a new timer to call `desktop-auto-save' in that many seconds."
+integer, start a new idle timer to call `desktop-auto-save' repeatedly
+after that many seconds of idle time."
   (when desktop-auto-save-timer
     (cancel-timer desktop-auto-save-timer)
     (setq desktop-auto-save-timer nil))
   (when (and (integerp desktop-auto-save-timeout)
              (> desktop-auto-save-timeout 0))
     (setq desktop-auto-save-timer
-          (run-with-timer desktop-auto-save-timeout nil
-                          'desktop-auto-save))))
+          (run-with-idle-timer desktop-auto-save-timeout t
+                               'desktop-auto-save))))
 
 ;; ----------------------------------------------------------------------------
 ;;;###autoload