Re: /srv/bzr/emacs/trunk r106599: message.el (message-pop-to-buffer): Use pop-to-buffer-same-window for last change.

[Katsumi Yamaoka <yamaoka@jpl.org>]

Chong Yidong wrote:
>   message.el (message-pop-to-buffer): Use pop-to-buffer-same-window
> for last change.
[...]

But there's no such function in old Emacsen nor XEmacsen.  Cf.
http://news.gmane.org/group/gmane.emacs.gnus.general/thread=80641

The main reason using it is to pop up a frame according to
'special-display-regexps' and friends, I guess.  So, I tried
a function that emulates `pop-to-buffer-same-window':

--- message.el~	2011-12-04 22:06:42.984375000 +0000
+++ message.el	2011-12-06 23:45:56.875000000 +0000
@@ -6388,7 +6388,15 @@
 			       "Message already being composed; erase? ")
 			    (message nil))))
 	    (error "Message being composed")))
-      (funcall (or switch-function #'pop-to-buffer-same-window) name)
+      (cond (switch-function
+	     (funcall switch-function name))
+	    ((fboundp 'pop-to-buffer-same-window)
+	     (pop-to-buffer-same-window name))
+	    (t
+	     (save-window-excursion
+	       (pop-to-buffer name))
+	     (unless (get-buffer-window name t)
+	       (set-window-buffer nil name))))
       (set-buffer name))
     (erase-buffer)
     (message-mode)))

Does this get a passing mark?
Tested with Emacs 23.3 and XEmacs 21.4.22.