def rotate(self):
v = (self.start[0]-self.end[0],self.start[1]-self.end[1])
angle = get_angle(v) + self.rad
center = ((self.start[0] + self.end[0])/2.0, (self.start[1] + self.end[1])/2.0)
temp = hanshu.vector_length(v)/2.0
self.start = (center[0]+temp*math.cos(angle),center[1] - temp * math.sin(angle))
self.end = (center[0]-temp*math.cos(angle),center[1] + temp * math.sin(angle))
def get_angle(x):
a = hanshu.vector_length(x)
return -1*math.acos(math.fabs(x[0])/a) if x[1]*x[0]>=0 else math.acos(math.fabs(x[0])/a)
