def _setProperty(self, _type, data, win=None, mask=None):
        """
        Send a ClientMessage event to the root window
        """
        if not win:
            win = self.root
        if type(data) is str:
            dataSize = 8
        else:
            data = (data+[0]*(5-len(data)))[:5]
            dataSize = 32

        ev = protocol.event.ClientMessage(
            window=win,
            client_type=self.display.get_atom(_type), data=(dataSize, data))

        if not mask:
            mask = (X.SubstructureRedirectMask | X.SubstructureNotifyMask)
        self.root.send_event(ev, event_mask=mask)
Send a ClientMessage event to the root window