--- mm-decode.el~	2013-01-30 09:41:37.287257600 +0000
+++ mm-decode.el	2013-02-27 09:20:30.267956900 +0000
@@ -814,6 +814,8 @@
 (declare-function gnus-configure-windows "gnus-win" (setting &optional force))
 (defvar mailcap-mime-extensions)	; mailcap-mime-info autoloads
 
+(defvar write-point)
+
 (defun mm-display-external (handle method)
   "Display HANDLE using METHOD."
   (let ((outbuf (current-buffer)))
@@ -950,9 +952,33 @@
 			    method file (mm-handle-type handle))))
 	      (unwind-protect
 		  (progn
+		    (setq buffer (generate-new-buffer " *mm*"))
+		    (let (wp)
+		      (with-current-buffer outbuf
+			(let ((point (point)))
+			  (forward-line 2)
+			  (setq wp (point))
+			  (goto-char point)))
+		      (with-current-buffer buffer
+			(set (make-local-variable 'write-point) wp)
+			(set (make-local-variable 'after-change-functions)
+			     `((lambda (st nd len)
+				 (when (buffer-live-p ,outbuf)
+				   (let (wp text)
+				     (with-current-buffer ,buffer
+				       (setq wp write-point
+					     text (buffer-substring st nd)
+					     write-point (+ wp (- nd st))))
+				     (with-current-buffer ,outbuf
+				       (let ((buffer-read-only nil)
+					     (point (point)))
+					 (goto-char wp)
+					 (mm-insert-inline
+					  ',handle (with-current-buffer ,buffer
+						     (buffer-substring st nd)))
+					 (goto-char point))))))))))
 		    (start-process "*display*"
-				   (setq buffer
-					 (generate-new-buffer " *mm*"))
+				   buffer
 				   shell-file-name
 				   shell-command-switch command)
 		    (set-process-sentinel
@@ -977,15 +1003,6 @@
 			   (condition-case nil
 			       (delete-directory (file-name-directory file))
 			     (error))
-			   (when (buffer-live-p outbuf)
-			     (with-current-buffer outbuf
-			       (let ((buffer-read-only nil)
-				     (point (point)))
-				 (forward-line 2)
-				 (mm-insert-inline
-				  handle (with-current-buffer buffer
-					   (buffer-string)))
-				 (goto-char point))))
 			   (when (buffer-live-p buffer)
 			     (kill-buffer buffer)))
 			 (message "Displaying %s...done" command)))))