update position text

def update_position(self):
        '''update position text'''
        state = self.state
        pos = self.mouse_pos
        newtext = ''
        alt = 0
        if pos is not None:
            (lat,lon) = self.coordinates(pos.x, pos.y)
            newtext += 'Cursor: %f %f (%s)' % (lat, lon, mp_util.latlon_to_grid((lat, lon)))
            if state.elevation:
                alt = self.ElevationMap.GetElevation(lat, lon)
                if alt is not None:
                    newtext += ' %.1fm' % alt
        state.mt.set_download(state.download)
        pending = 0
        if state.download:
            pending = state.mt.tiles_pending()
        if pending:
            newtext += ' Map Downloading %u ' % pending
        if alt == -1:
            newtext += ' SRTM Downloading '
        newtext += '\n'
        if self.click_pos is not None:
            newtext += 'Click: %f %f (%s %s) (%s)' % (self.click_pos[0], self.click_pos[1],
                                                      mp_util.degrees_to_dms(self.click_pos[0]),
                                                      mp_util.degrees_to_dms(self.click_pos[1]),
                                                      mp_util.latlon_to_grid(self.click_pos))
        if self.last_click_pos is not None:
            distance = mp_util.gps_distance(self.last_click_pos[0], self.last_click_pos[1],
                                            self.click_pos[0], self.click_pos[1])
            bearing = mp_util.gps_bearing(self.last_click_pos[0], self.last_click_pos[1],
                                            self.click_pos[0], self.click_pos[1])
            newtext += '  Distance: %.1fm Bearing %.1f' % (distance, bearing)
        if newtext != state.oldtext:
            self.position.Clear()
            self.position.WriteText(newtext)
            state.oldtext = newtext