-// clip.cpp
-int clip_rect (double& x1, double& y1, double& x2, double& y2, const double rect[4]);
-int clip_segment (double& x1, double& y1, double& x2, double& y2, const double u, const double v);
-int clip_sector (double& x1, double& y1, double& x2, double& y2, const double u, const double v);
-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);
+// clip.cpp
+bool clip_rect (double& x1, double& y1, double& x2, double& y2, const double rect[4]);
+bool clip_segment (double& x1, double& y1, double& x2, double& y2, const double u, const double v);
+bool clip_sector (double& x1, double& y1, double& x2, double& y2, const double u, const double v);
+bool clip_circle (double& x1, double& y1, double& x2, double& y2, const double cx, const double cy, const double radius, double t1, double t2);
+bool clip_triangle (double& x1, double& y1, double& x2, double& y2, const double u, const double v, const int clip_xaxis);