+(defun notmuch-show--mm-display-part (handle)
+ "Use mm-display-part to display HANDLE in a new buffer.
+
+If the part is displayed in an external application then close
+the new buffer."
+ (let ((buf (get-buffer-create (generate-new-buffer-name
+ (concat " *notmuch-internal-part*")))))
+ (switch-to-buffer buf)
+ (if (eq (mm-display-part handle) 'external)
+ (kill-buffer buf)
+ (goto-char (point-min))
+ (set-buffer-modified-p nil)
+ (view-buffer buf 'kill-buffer-if-not-modified))))
+
+(defun notmuch-show-choose-mime-of-part (mime-type)
+ "Choose the mime type to use for displaying part"
+ (interactive
+ (list (completing-read "Mime type to use (default text/plain): "
+ (mailcap-mime-types) nil nil nil nil "text/plain")))
+ (notmuch-show-apply-to-current-part-handle #'notmuch-show--mm-display-part mime-type))
+