(defun gnus-mime-view-part-as-type-internal ()
  (gnus-article-check-buffer)
  (let* ((name (mail-content-type-get
		(mm-handle-type (get-text-property (point) 'gnus-data))
		'name))
	 (def-type (and name (mm-default-file-encoding name))))
    (and def-type (cons def-type 0))))

(defun gnus-mime-view-part-as-type (mime-type)
  "Choose a MIME media type, and view the part as such."
  (interactive
   (list (completing-read
	  "View as MIME type: "
	  (mapcar (lambda (i) (list i i)) (mailcap-mime-types))
	  nil nil
	  (gnus-mime-view-part-as-type-internal))))
  (gnus-article-check-buffer)
  (let* ((handle (get-text-property (point) 'gnus-data)))
    (gnus-mm-display-part
     (mm-make-handle (mm-handle-buffer handle)
		     (cons mime-type (cdr (mm-handle-type handle)))
		     (mm-handle-encoding handle)
		     (mm-handle-undisplayer handle)
		     (mm-handle-disposition handle)
		     (mm-handle-description handle)
		     (mm-handle-cache handle)
		     (mm-handle-id handle)))))