Index: trunk/src/obj_arc.c
===================================================================
--- trunk/src/obj_arc.c	(revision 18629)
+++ trunk/src/obj_arc.c	(revision 18630)
@@ -319,6 +319,27 @@
 	return pcb_arc_bbox_(arc, 1);
 }
 
+void pcb_arc_pre(pcb_arc_t *arc)
+{
+	pcb_layer_t *ly = pcb_layer_get_real(arc->parent.layer);
+	if (ly == NULL)
+		return;
+	if (ly->arc_tree != NULL)
+		pcb_r_delete_entry(ly->arc_tree, (pcb_box_t *)arc);
+	pcb_poly_restore_to_poly(ly->parent.data, PCB_OBJ_ARC, ly, arc);
+}
+
+void pcb_arc_post(pcb_arc_t *arc)
+{
+	pcb_layer_t *ly = pcb_layer_get_real(arc->parent.layer);
+	if (ly == NULL)
+		return;
+	if (ly->arc_tree != NULL)
+		pcb_r_insert_entry(ly->arc_tree, (pcb_box_t *)arc);
+	pcb_poly_clear_from_poly(ly->parent.data, PCB_OBJ_ARC, ly, arc);
+}
+
+
 /***** operations *****/
 
 /* copies an arc to buffer */
Index: trunk/src/obj_arc.h
===================================================================
--- trunk/src/obj_arc.h	(revision 18629)
+++ trunk/src/obj_arc.h	(revision 18630)
@@ -84,7 +84,12 @@
 /* ptr3 values for start and end point */
 extern int *pcb_arc_start_ptr, *pcb_arc_end_ptr;
 
+/* un-administrate a arc; call before changing geometry */
+void pcb_arc_pre(pcb_arc_t *arc);
 
+/* re-administrate a arc; call after changing geometry */
+void pcb_arc_post(pcb_arc_t *arc);
+
 #define	pcb_arc_move(a,dx,dy)                                     \
 	do {                                                            \
 		pcb_coord_t __dx__ = (dx), __dy__ = (dy);                     \