Index: layer_grp.h
===================================================================
--- layer_grp.h	(revision 8680)
+++ layer_grp.h	(revision 8681)
@@ -107,6 +107,10 @@
 /* Insert a new layer group in the layer stack after the specified group */
 pcb_layer_group_t *pcb_layergrp_insert_after(pcb_board_t *pcb, pcb_layergrp_id_t where);
 
+/* Move lid 1 step towards the front (delta=-1) or end (delta=+1) of the
+   layer list of the group. Return 0 on success (even when already reached
+   the end of the list) or -1 on error */
+int pcb_layergrp_step_layer(pcb_layer_group_t *grp, pcb_layer_id_t lid, int delta);
 
 /* Enable/disable inhibition of layer changed events during layer group updates */
 void pcb_layergrp_inhibit_inc(void);