Some desktop doc

* doc/emacs/misc.texi (Saving Emacs Sessions):
Mention desktop-auto-save-timeout.

* lisp/desktop.el (desktop-save-mode, desktop-auto-save-timeout): Doc fixes.

* etc/NEWS: Related edit.

doc/emacs/ChangeLog

+2014-02-18  Glenn Morris  <rgm@gnu.org>
+
+	* misc.texi (Saving Emacs Sessions): Mention desktop-auto-save-timeout.
+
 2014-02-17  Stefan Monnier  <monnier@iro.umontreal.ca>
 
 	* programs.texi (Matching): Fix typo.

doc/emacs/misc.texi

@@ -2150,6 +2150,12 @@ sessions, or add this line in your init file (@pxref{Init File}):
 (desktop-save-mode 1)
 @end example
 
+@vindex desktop-auto-save-timeout
+@noindent
+When @code{desktop-save-mode} is active and the desktop file exists,
+Emacs auto-saves it every @code{desktop-auto-save-timeout}
+seconds, if that is non-@code{nil} and non-zero.
+
 @findex desktop-change-dir
 @findex desktop-revert
 @vindex desktop-path

etc/NEWS

@@ -468,8 +468,10 @@ if your version doesn't support that option.  See option `cfengine-cf-promises'.
 
 ** Desktop
 
-*** `desktop-auto-save-timeout' defines the number of seconds idle time
-before auto-save of the desktop.
++++
+*** `desktop-save-mode' by default now auto-saves an existing desktop file
+after `desktop-auto-save-timeout'.  To disable this, customize that option
+to nil (or zero).
 
 *** `desktop-restore-frames', enabled by default, allows saving and
 restoring the frame/window configuration (frameset).  Additional options

lisp/ChangeLog

+2014-02-18  Glenn Morris  <rgm@gnu.org>
+
+	* desktop.el (desktop-save-mode, desktop-auto-save-timeout): Doc fixes.
+
 2014-02-17  Alan Mackenzie  <acm@muc.de>
 
 	Connect electric-indent-mode up with CC Mode.  Bug #15478.

lisp/desktop.el

 ;;; desktop.el --- save partial status of Emacs when killed -*- lexical-binding: t -*-
 
-;; Copyright (C) 1993-1995, 1997, 2000-2014 Free Software Foundation,
-;; Inc.
+;; Copyright (C) 1993-1995, 1997, 2000-2014 Free Software Foundation, Inc.
 
 ;; Author: Morten Welinder <terra@diku.dk>
 ;; Keywords: convenience
@@ -154,13 +153,24 @@ backward compatibility.")
 ;;;###autoload
 (define-minor-mode desktop-save-mode
   "Toggle desktop saving (Desktop Save mode).
-With a prefix argument ARG, enable Desktop Save mode if ARG is
-positive, and disable it otherwise.  If called from Lisp, enable
-the mode if ARG is omitted or nil.
+With a prefix argument ARG, enable Desktop Save mode if ARG is positive,
+and disable it otherwise.  If called from Lisp, enable the mode if ARG
+is omitted or nil.
 
-If Desktop Save mode is enabled, the state of Emacs is saved from
-one session to another.  See variable `desktop-save' and function
-`desktop-read' for details."
+When Desktop Save mode is enabled, the state of Emacs is saved from
+one session to another.  In particular, Emacs will save the desktop when
+it exits (this may prompt you; see the option `desktop-save').  The next
+time Emacs starts, if this mode is active it will restore the desktop.
+
+To manually save the desktop at any time, use the command `M-x desktop-save'.
+To load it, use `M-x desktop-read'.
+
+Once a desktop file exists, Emacs will auto-save it according to the
+option `desktop-auto-save-timeout'.
+
+To see all the options you can set, browse the `desktop' customization group.
+
+For further details, see info node `(emacs)Saving Emacs Sessions'."
   :global t
   :group 'desktop
   (if desktop-save-mode
@@ -197,6 +207,7 @@ determine where the desktop is saved."
 
 (defcustom desktop-auto-save-timeout auto-save-timeout
   "Number of seconds idle time before auto-save of the desktop.
+This applies to an existing desktop file when `desktop-save-mode' is enabled.
 Zero or nil means disable auto-saving due to idleness."
   :type '(choice (const :tag "Off" nil)
                  (integer :tag "Seconds"))
@@ -1055,6 +1066,7 @@ being set (usually, by reading it from the desktop)."
 (defvar desktop-buffer-ok-count)
 (defvar desktop-buffer-fail-count)
 
+;; FIXME Interactively, this should have the option to prompt for dirname.
 ;;;###autoload
 (defun desktop-read (&optional dirname)
   "Read and process the desktop file in directory DIRNAME.