Index: trunk/src/layer.c
===================================================================
--- trunk/src/layer.c	(revision 12537)
+++ trunk/src/layer.c	(revision 12538)
@@ -637,6 +637,33 @@
 	dst->polygon_tree = src->polygon_tree;
 }
 
+
+void pcb_layer_real2bound_offs(pcb_layer_t *dst, pcb_board_t *src_pcb, pcb_layer_t *src)
+{
+	dst->meta.bound.real = NULL;
+	dst->is_bound = 1;
+	if ((dst->meta.bound.type & PCB_LYT_INTERN) && (dst->meta.bound.type & PCB_LYT_COPPER)) {
+		int from_top, from_bottom, res;
+		pcb_layergrp_t *tcop = pcb_get_grp(&src_pcb->LayerGroups, PCB_LYT_TOP, PCB_LYT_COPPER);
+		pcb_layergrp_t *bcop = pcb_get_grp(&src_pcb->LayerGroups, PCB_LYT_BOTTOM, PCB_LYT_COPPER);
+		pcb_layergrp_id_t tcop_id = pcb_layergrp_id(src_pcb, tcop);
+		pcb_layergrp_id_t bcop_id = pcb_layergrp_id(src_pcb, bcop);
+
+		res = pcb_layergrp_dist(src_pcb, src->meta.real.grp, tcop_id, PCB_LYT_COPPER, &from_top);
+		res |= pcb_layergrp_dist(src_pcb, src->meta.real.grp, bcop_id, PCB_LYT_COPPER, &from_bottom);
+		if (res == 0) {
+			if (from_top <= from_bottom)
+				dst->meta.bound.stack_offs = from_top;
+			else
+				dst->meta.bound.stack_offs = -from_bottom;
+		}
+		else
+			pcb_message(PCB_MSG_ERROR, "Internal error: can't figure the inter copper\nlayer offset for %s\n", src->name);
+	}
+	else
+		dst->meta.bound.stack_offs = 0;
+}
+
 void pcb_layer_real2bound(pcb_layer_t *dst, pcb_layer_t *src, int share_rtrees)
 {
 	pcb_board_t *pcb;
@@ -645,16 +672,7 @@
 
 	pcb = pcb_layer_get_top(src);
 	dst->comb = src->comb;
-	dst->is_bound = 1;
 
-	if (!src->is_bound) {
-		dst->meta.bound.real = src;
-		if (share_rtrees)
-			pcb_layer_link_trees(dst, src);
-	}
-	else
-		dst->meta.bound.real = NULL;
-
 	dst->meta.bound.type = pcb_layergrp_flags(pcb, src->meta.real.grp);
 	if (src->name != NULL)
 		dst->name = pcb_strdup(src->name);
@@ -661,22 +679,13 @@
 	else
 		dst->name = NULL;
 
-	if ((dst->meta.bound.type & PCB_LYT_INTERN) && (dst->meta.bound.type & PCB_LYT_COPPER)) {
-		int from_top, from_bottom, res;
-		
-		res = pcb_layergrp_dist(pcb, src->meta.real.grp, pcb_layergrp_get_top_copper(), PCB_LYT_COPPER, &from_top);
-		res |= pcb_layergrp_dist(pcb, src->meta.real.grp, pcb_layergrp_get_bottom_copper(), PCB_LYT_COPPER, &from_bottom);
-		if (res == 0) {
-			if (from_top <= from_bottom)
-				dst->meta.bound.stack_offs = from_top;
-			else
-				dst->meta.bound.stack_offs = -from_bottom;
-		}
-		else
-			pcb_message(PCB_MSG_ERROR, "Internal error: can't figure the inter copper\nlayer offset for %s\n", src->name);
+	pcb_layer_real2bound_offs(dst, pcb, src);
+
+	if (!src->is_bound) {
+		dst->meta.bound.real = src;
+		if (share_rtrees)
+			pcb_layer_link_trees(dst, src);
 	}
-	else
-		dst->meta.bound.stack_offs = 0;
 }
 
 pcb_layer_t *pcb_layer_resolve_binding(pcb_board_t *pcb, pcb_layer_t *src)
Index: trunk/src/layer.h
===================================================================
--- trunk/src/layer.h	(revision 12537)
+++ trunk/src/layer.h	(revision 12538)
@@ -251,6 +251,11 @@
 int pcb_layer_move(pcb_board_t *pcb, pcb_layer_id_t old_index, pcb_layer_id_t new_index, pcb_layergrp_id_t new_in_grp);
 
 
+/* set up dst to be a bound layer with the right offset in the stack; src_pcb
+   is used for the layer stack of src. Assumes other fields of dst, e.g. name,
+   are all set up. */
+void pcb_layer_real2bound_offs(pcb_layer_t *dst, pcb_board_t *src_pcb, pcb_layer_t *src);
+
 /* Set up dst so that it's a non-real layer bound to src */
 void pcb_layer_real2bound(pcb_layer_t *dst, pcb_layer_t *src, int share_rtrees);