set element visualization drawing
            
        :param p0: start drawing position, (x,y)
        :param angle: angle [deg] between x-axis, angle is rotating from x-axis to be '+' or '-', '+': clockwise, '-': anticlockwise
        :param mode: artist mode, 'plain' or 'fancy', 'plain' by default

def setDraw(self, p0=(0, 0), angle=0, mode='plain'):
        """ set element visualization drawing
            
        :param p0: start drawing position, (x,y)
        :param angle: angle [deg] between x-axis, angle is rotating from x-axis to be '+' or '-', '+': clockwise, '-': anticlockwise
        :param mode: artist mode, 'plain' or 'fancy', 'plain' by default
        """
        sconf = self.getConfig(type='simu')
        if 'l' in sconf:
            self._style['length'] = float(sconf['l'])
        else:
            self._style['length'] = 0
        self._style['angle'] = angle
        _theta = angle / 180.0 * np.pi  # deg to rad
        _length = self._style['length']
        _lw = self._style['lw']
        _color = self._style['color']
        _alpha = self._style['alpha']

        #
        # --p0-------p1--
        # 
        if mode == 'plain':
            x0, y0 = p0
            x1, y1 = x0 + _length, y0 + _length * np.tan(_theta)
            vs = [(x0, y0), (x1, y1)]
            cs = [Path.MOVETO, Path.LINETO]
            pth = Path(vs, cs)
            ptch = patches.PathPatch(pth, lw=_lw, fc=_color, ec=_color, alpha=_alpha)
            self._patches = []
            self._patches.append(ptch)
            self.next_p0 = x1, y1
            self.next_inc_angle = 0
        else:  # fancy mode, same as plain, could be more fancy(Apr.08, 2016)
            x0, y0 = p0
            x1, y1 = x0 + _length, y0 + _length * np.tan(_theta)
            vs = [(x0, y0), (x1, y1)]
            cs = [Path.MOVETO, Path.LINETO]
            pth = Path(vs, cs)
            ptch = patches.PathPatch(pth, lw=_lw, fc=_color, ec=_color, alpha=_alpha)
            self._patches = []
            self._patches.append(ptch)
            self.next_p0 = x1, y1
            self.next_inc_angle = 0