Index: work/gtk/layersel/layersel.c
===================================================================
--- work/gtk/layersel/layersel.c	(revision 8551)
+++ work/gtk/layersel/layersel.c	(revision 8552)
@@ -120,6 +120,11 @@
 
 /*** Event handling ***/
 
+static int ev_lyr_no_select(layersel_layer_t *lsl)
+{
+	return 1; /* layer can not be selected ever */
+}
+
 static gboolean group_vis_press_cb(GtkWidget *widget, GdkEvent *event, layersel_grp_t *lsg)
 {
 	switch(event->button.button) {
@@ -139,7 +144,8 @@
 	layersel_layer_t *lsl = user_data;
 	switch(event->button.button) {
 		case 1:
-			lsl->on = !lsl->on;
+			if ((lsl->ev_toggle_vis == NULL) || (lsl->ev_toggle_vis(lsl) == 0))
+				lsl->on = !lsl->on;
 			layer_vis_sync(lsl);
 			break;
 		case 3:
@@ -155,11 +161,13 @@
 	switch(event->button.button) {
 		case 1:
 			printf("layer select!\n");
-			old_curr = current;
-			current = lsl;
-			if (old_curr != NULL)
-				layer_vis_sync(old_curr);
-			layer_vis_sync(lsl);
+			if ((lsl->ev_selected == NULL) || (lsl->ev_selected(lsl) == 0)) {
+				old_curr = current;
+				current = lsl;
+				if (old_curr != NULL)
+					layer_vis_sync(old_curr);
+				layer_vis_sync(lsl);
+			}
 			break;
 		case 3:
 			pcb_hid_actionl("Popup", "layer", NULL);
@@ -338,6 +346,12 @@
 		gtk_box_pack_start(GTK_BOX(lsg->layers), build_layer(lsg, &lsg->layer[1], "Vias"), FALSE, FALSE, 1);
 		gtk_box_pack_start(GTK_BOX(lsg->layers), build_layer(lsg, &lsg->layer[2], "Far side"), FALSE, FALSE, 1);
 		gtk_box_pack_start(GTK_BOX(lsg->layers), build_layer(lsg, &lsg->layer[3], "All-silk"), FALSE, FALSE, 1);
+
+		lsg->layer[0].ev_selected = ev_lyr_no_select;
+		lsg->layer[1].ev_selected = ev_lyr_no_select;
+		lsg->layer[2].ev_selected = ev_lyr_no_select;
+		lsg->layer[3].ev_selected = ev_lyr_no_select;
+
 		build_group_finish(lsg);
 	}
 
Index: work/gtk/layersel/layersel.h
===================================================================
--- work/gtk/layersel/layersel.h	(revision 8551)
+++ work/gtk/layersel/layersel.h	(revision 8552)
@@ -10,6 +10,9 @@
 struct layersel_layer_s {
 	GtkWidget *box, *vis_on, *vis_off, *name_box;
 
+	int (*ev_toggle_vis)(layersel_layer_t *lsl); /* called first in click handler, if returns non-zero, normal visibility update is supressed */
+	int (*ev_selected)(layersel_layer_t *lsl);   /* called first in click handler, if returns non-zero, layer can not be selected */
+
 	unsigned on:1; /* TODO: temporary hack: should be extracted from the layer struct */
 
 	/* for callbacks */