int clip_circle (double& x1, double& y1, double& x2, double& y2, const double cx, const double cy, const double radius, double t1, double t2);
int clip_triangle (double& x1, double& y1, double& x2, double& y2, const double u, const double v, const int clip_xaxis);
int clip_circle (double& x1, double& y1, double& x2, double& y2, const double cx, const double cy, const double radius, double t1, double t2);
int clip_triangle (double& x1, double& y1, double& x2, double& y2, const double u, const double v, const int clip_xaxis);