Index: trunk/src/obj_line.c
===================================================================
--- trunk/src/obj_line.c	(revision 20161)
+++ trunk/src/obj_line.c	(revision 20162)
@@ -61,6 +61,24 @@
 
 /**** allocation ****/
 
+void pcb_line_reg(pcb_layer_t *layer, pcb_line_t *line)
+{
+	linelist_append(&layer->Line, line);
+	assert(layer->parent_type == PCB_PARENT_DATA);
+	pcb_obj_id_reg(layer->parent.data, line);
+	PCB_SET_PARENT(line, layer, layer);
+}
+
+void pcb_line_unreg(pcb_line_t *line)
+{
+	pcb_layer_t *layer = line->parent.layer;
+	assert(line->parent_type == PCB_PARENT_LAYER);
+	linelist_remove(line);
+	assert(layer->parent_type == PCB_PARENT_DATA);
+	pcb_obj_id_del(layer->parent.data, line);
+	PCB_SET_PARENT(line, layer, NULL);
+}
+
 pcb_line_t *pcb_line_alloc(pcb_layer_t * layer)
 {
 	pcb_line_t *new_obj;
@@ -68,17 +86,16 @@
 	new_obj = calloc(sizeof(pcb_line_t), 1);
 	new_obj->type = PCB_OBJ_LINE;
 	new_obj->Attributes.post_change = pcb_obj_attrib_post_change;
-	PCB_SET_PARENT(new_obj, layer, layer);
 
-	linelist_append(&layer->Line, new_obj);
+	pcb_line_reg(layer, new_obj);
 
 	return new_obj;
 }
 
-void pcb_line_free(pcb_line_t * data)
+void pcb_line_free(pcb_line_t *line)
 {
-	linelist_remove(data);
-	free(data);
+	pcb_line_unreg(line);
+	free(line);
 }
 
 
@@ -408,8 +425,8 @@
 	pcb_poly_restore_to_poly(ctx->buffer.src, PCB_OBJ_LINE, srcly, line);
 	pcb_r_delete_entry(srcly->line_tree, (pcb_box_t *)line);
 
-	linelist_remove(line);
-	linelist_append(&(dstly->Line), line);
+	pcb_line_unreg(line);
+	pcb_line_reg(dstly, line);
 
 	PCB_FLAG_CLEAR(PCB_FLAG_FOUND, line);
 
@@ -418,8 +435,6 @@
 	pcb_r_insert_entry(dstly->line_tree, (pcb_box_t *)line);
 	pcb_poly_clear_from_poly(ctx->buffer.dst, PCB_OBJ_LINE, dstly, line);
 
-	PCB_SET_PARENT(line, layer, dstly);
-
 	return line;
 }
 
@@ -636,8 +651,8 @@
 {
 	pcb_r_delete_entry(Source->line_tree, (pcb_box_t *) line);
 
-	linelist_remove(line);
-	linelist_append(&(Destination->Line), line);
+	pcb_line_unreg(line);
+	pcb_line_reg(Destination, line);
 
 	if (!Destination->line_tree)
 		Destination->line_tree = pcb_r_create_tree();
Index: trunk/src/obj_line.h
===================================================================
--- trunk/src/obj_line.h	(revision 20161)
+++ trunk/src/obj_line.h	(revision 20162)
@@ -57,6 +57,8 @@
 pcb_line_t *pcb_line_dup_at(pcb_layer_t *dst, pcb_line_t *src, pcb_coord_t dx, pcb_coord_t dy);
 void *pcb_line_destroy(pcb_layer_t *dst, pcb_line_t *src);
 
+void pcb_line_reg(pcb_layer_t *layer, pcb_line_t *line);
+void pcb_line_unreg(pcb_line_t *line);
 
 /* Add objects without creating them or making any "sanity modifications" to them */
 void pcb_add_line_on_layer(pcb_layer_t *Layer, pcb_line_t *Line);
Index: trunk/src/obj_subc.c
===================================================================
--- trunk/src/obj_subc.c	(revision 20161)
+++ trunk/src/obj_subc.c	(revision 20162)
@@ -462,9 +462,8 @@
 			}
 			else {
 				/* copy the line */
-				linelist_remove(line);
-				linelist_append(&dst->Line, line);
-				PCB_SET_PARENT(line, layer, dst);
+				pcb_line_unreg(line);
+				pcb_line_reg(dst, line);
 				PCB_FLAG_CLEAR(PCB_FLAG_WARN | PCB_FLAG_FOUND | PCB_FLAG_SELECTED, line);
 
 				if (termpad != NULL) {