(defun my-external-readonly-split ()
    "Open the current file in an external xfce4-terminal as read-only."
    (interactive)
    (if buffer-file-name
        (start-process "xfce-terminal-split" nil 
                       "xfce4-terminal" "-x" "emacs" "-nw" 
                       "--eval" "(find-file-read-only (pop command-line-args-left))"
                       buffer-file-name)
      (message "Current buffer is not visiting a file!")))

  (global-set-key (kbd "C-x 4") 'my-external-readonly-split)