def on_click(self, button, button_state, cursor_x, cursor_y):
        """ Mouse button clicked.
            Glut calls this function when a mouse button is
            clicked or released.
        """
        self.isdragging = False
        if button == glut.GLUT_LEFT_BUTTON and button_state == glut.GLUT_UP:
            # Left button released
            self.lastrot = copy.copy(self.thisrot)  # Set Last Static Rotation To Last Dynamic One
        elif button == glut.GLUT_LEFT_BUTTON and button_state == glut.GLUT_DOWN:
            # Left button clicked down
            self.lastrot = copy.copy(self.thisrot)  # Set Last Static Rotation To Last Dynamic One
            self.isdragging = True  # Prepare For Dragging
            mouse_pt = arcball.Point2fT(cursor_x, cursor_y)
            self.arcball.click(mouse_pt)  # Update Start Vector And Prepare For Dragging
        elif button == glut.GLUT_RIGHT_BUTTON and button_state == glut.GLUT_DOWN:
            # If a mouse click location was requested, return it to caller
            if hasattr(self, 'event_port'):
                self.mouseclick_port = self.event_port
                del self.event_port
            if hasattr(self, 'mouseclick_port'):
                self.send_mouseclick_to_caller(cursor_x, cursor_y)
        elif button == glut.GLUT_MIDDLE_BUTTON and button_state == glut.GLUT_DOWN:
            # If a mouse click location was requested, return it to caller
            if hasattr(self, 'event_port'):
                self.mouseclick_port = self.event_port
                del self.event_port
            if hasattr(self, 'mouseclick_port'):
                self.send_mouseclick_to_caller(cursor_x, cursor_y, button='middle')
        glut.glutPostRedisplay()
Mouse button clicked.
            Glut calls this function when a mouse button is
            clicked or released.