Index: polygon.h
===================================================================
--- polygon.h	(revision 10208)
+++ polygon.h	(revision 10209)
@@ -96,5 +96,8 @@
 
 pcb_bool pcb_pline_is_rectangle(pcb_pline_t *pl);
 
+/* clear np1 from the polygon; also free np1 if fnp is true. Returns 1 on
+   success. */
+int pcb_poly_subtract(pcb_polyarea_t *np1, pcb_polygon_t *p, pcb_bool fnp);
 
 #endif