modulargroup.py 文件源码

def arc_to(self, x1, y1):
        x0, y0 = self.get_current_point()
        dx, dy = x1 - x0, y1 - y0

        if abs(dx) < 1e-8:
            self.line_to(x1, y1)

        else:
            center = 0.5 * (x0 + x1) + 0.5 * (y0 + y1) * dy / dx
            theta0 = cmath.phase(x0 - center + y0*1j)
            theta1 = cmath.phase(x1 - center + y1*1j)
            r = abs(x0 - center + y0*1j)

            # we must ensure that the arc ends at (x1, y1)
            if x0 < x1:
                self.arc_negative(center, 0, r, theta0, theta1)
            else:
                self.arc(center, 0, r, theta0, theta1)