def queue_command(self, command):
        """Put a command on the queue to be called in the component's
        thread.

        :param callable command: the method to be invoked, e.g.
            :py:meth:`~Component.new_frame_event`.

        """
        if self._running:
            # queue event normally
            QtCore.QCoreApplication.postEvent(
                self, ActionEvent(command), QtCore.Qt.LowEventPriority)
        else:
            # save event until we are started
            self._incoming.append(command)