let prompt_command (w : gui_window) =
  let mb = w#minibuffer in
  let on_return com =
    match Ed_misc.no_blanks com with
      "" -> ()
    | _ -> Cam_commands.eval_command com
  in
  Ed_misc.select_string
    ~history: prompt_command_history
    mb ~title: "Command"
    ~choices: (Cam_commands.available_command_names ())
    ""
    on_return