Index: lisp/simple.el
===================================================================
RCS file: /sources/emacs/emacs/lisp/simple.el,v
retrieving revision 1.899
diff -u -r1.899 simple.el
--- lisp/simple.el	1 Feb 2008 16:01:05 -0000	1.899
+++ lisp/simple.el	5 Feb 2008 05:49:19 -0000
@@ -3323,11 +3323,55 @@
     (setq mark-active nil)
     (run-hooks 'deactivate-mark-hook))))
 
+
+(defun set-select-active-regions (opt val)
+  (setq select-active-regions val)
+  (setq select-active-regions-last-region nil)
+  (if val
+      (progn
+	(funcall 'cancel-function-timers 
+	 'maybe-select-for-select-active-regions)
+	(run-with-idle-timer 
+	 0 t'maybe-select-for-select-active-regions))
+    (funcall 'cancel-function-timers 
+     'maybe-select-for-select-active-regions)))
+
+
 (defcustom select-active-regions nil
   "If non-nil, an active region automatically becomes the window selection."
   :type 'boolean
   :group 'killing
-  :version "23.1")
+  :version "23.1"
+  :risky t
+  :set 'set-select-active-regions)
+
+
+
+(defvar select-active-regions-last-region nil
+  "record of last propagated region for comparison.")
+
+(defun maybe-select-for-select-active-regions ()
+  "Implements `select-active-regions'. Called by timer
+`select-active-regions-timer' and `set-mark'"
+  (and select-active-regions
+       (region-active-p)
+       (let ((current-region-text
+	      (buffer-substring (region-beginning) (region-end))))
+	 (if (or (null select-active-regions-last-region)
+		 (not (string= select-active-regions-last-region
+			       current-region-text)))
+	     (if (or (null current-region-text) 
+		     (string= "" current-region-text))
+		 ;; don't propagate if this region is empty, but this 
+		 ;; region being empty means future nonempty regions 
+		 ;; need repropagation
+		 (setq select-active-regions-last-region nil)
+	       ;; this should be a call to interprogram-highlight-function
+	       ;; if/when that is introduced.
+	       (x-set-selection nil current-region-text)
+	       (setq select-active-regions-last-region 
+		     current-region-text))))))
+		 
 
 (defun set-mark (pos)
   "Set this buffer's mark to POS.  Don't use this function!
@@ -3351,8 +3395,9 @@
 	(setq mark-active t)
 	(run-hooks 'activate-mark-hook)
 	(and select-active-regions
-	     (x-set-selection
-	      nil (buffer-substring (region-beginning) (region-end))))
+	     ;; force repropagate if mark is reset
+	     (progn (setq select-active-regions-last-region nil)
+		    (maybe-select-for-select-active-regions)))
 	(set-marker (mark-marker) pos (current-buffer)))
     ;; Normally we never clear mark-active except in Transient Mark mode.
     ;; But when we actually clear out the mark value too,
Index: lisp/loadup.el
===================================================================
RCS file: /sources/emacs/emacs/lisp/loadup.el,v
retrieving revision 1.160
diff -u -r1.160 loadup.el
--- lisp/loadup.el	1 Feb 2008 22:43:10 -0000	1.160
+++ lisp/loadup.el	5 Feb 2008 05:49:19 -0000
@@ -82,6 +82,8 @@
 (message "%s" (garbage-collect))
 (load "loaddefs.el")  ;Don't get confused if someone compiled this by mistake.
 (message "%s" (garbage-collect))
+
+(load "emacs-lisp/timer") ; select-active-region in simple.el needs timer. 
 (load "simple")
 
 (load "help")
@@ -145,7 +147,6 @@
       (and (boundp 'x-toolkit-scroll-bars)
 	   (load "scroll-bar"))
       (load "select")))
-(load "emacs-lisp/timer")
 (load "isearch")
 (load "rfn-eshadow")