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diff --git a/polygon/math_for_graphics.h b/polygon/math_for_graphics.h
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+#ifndef MATH_FOR_GRAPHICS_H
+#define MATH_FOR_GRAPHICS_H
+// math stuff for graphics, from FreePCB
+
+/* Function FindLineSegmentIntersection
+ * find intersection between line y = a + bx and line segment (xi,yi) to (xf,yf)
+ * if b > DBL_MAX/10, assume vertical line at x = a
+ * return false if no intersection or true if intersect
+ * return coords of intersections in *x1, *y1, *x2, *y2
+ * if no intersection, returns min distance in dist
+ */
+bool FindLineSegmentIntersection( double a, double b, int xi, int yi, int xf, int yf,
+                double * x1, double * y1, double * x2, double * y2, double * dist=NULL );
+
+/* Function FindSegmentIntersections
+ * find intersections between line segment (xi,yi) to (xf,yf)
+ * and line segment (xi2,yi2) to (xf2,yf2)
+ * returns true if intersection found
+ */
+bool FindSegmentIntersections( int xi, int yi, int xf, int yf,
+                              int xi2, int yi2, int xf2, int yf2 );
+
+/**
+ * Function TestForIntersectionOfStraightLineSegments
+ * Test for intersection of line segments
+ * If lines are parallel, returns false
+ * If true, returns also intersection coords in x, y
+ * if false, returns min. distance in dist (may be 0.0 if parallel)
+ * and coords on nearest point in one of the segments in (x,y)
+ * @param x1i, y1i, x1f, y1f = integer coordinates of the first segment
+ * @param x2i, y2i, x2f, y2f = integer coordinates of the other segment
+ * @param x, y  = pointers on 2 integer to store the intersection coordinates (can be NULL)
+ * @param dist  = pointeur on a double to store the dist.
+ * @return true if intersect.
+ */
+bool TestForIntersectionOfStraightLineSegments( int x1i, int y1i, int x1f, int y1f,
+                                       int x2i, int y2i, int x2f, int y2f,
+                                       int * x=NULL, int * y=NULL, double * dist=NULL );
+
+/* Function GetClearanceBetweenSegments
+ * Get clearance between 2 segments
+ * Returns coordinates of the closest point between these 2 segments in x, y
+ * If clearance > max_cl, just returns max_cl+1 and doesn't return x,y
+ */
+int GetClearanceBetweenSegments( int x1i, int y1i, int x1f, int y1f, int w1,
+                                   int x2i, int y2i, int x2f, int y2f, int w2,
+                                   int max_cl, int * x, int * y );
+
+/**
+ * Function GetPointToLineSegmentDistance
+ * Get distance between line segment and point
+ * @param x,y = point
+ * @param xi,yi, xf,yf = the end-points of the line segment
+ * @return the distance
+ */
+double GetPointToLineSegmentDistance( int x, int y, int xi, int yi, int xf, int yf );
+
+/* Function GetPointToLineDistance
+ * Get min. distance from (x,y) to line y = a + bx
+ * if b > DBL_MAX/10, assume vertical line at x = a
+ * returns closest point on line in xpp, ypp
+ */
+double GetPointToLineDistance( double a, double b, int x, int y, 
+                               double * xp=NULL, double * yp=NULL );
+
+inline double Distance( double x1, double y1, double x2, double y2 )
+{
+    return hypot( x1 - x2, y1 - y2 );
+}
+
+#endif