--- trunk/src/map-tool.c	2009/10/28 11:50:37	147
+++ trunk/src/map-tool.c	2009/10/28 11:57:54	148
@@ -109,14 +109,18 @@
 
 static gboolean map_gps_update(gpointer data) {
   map_context_t *context = (map_context_t*)data;
+  static gboolean goto_is_enabled = FALSE;
 
   /* get reference position ... */
   pos_t *refpos = get_pos(context->appdata);
   gboolean ok = (refpos!= NULL) && !isnan(refpos->lat) && !isnan(refpos->lon);
 
   /* ... and enable "goto" button if it's valid */
-  osm_gps_map_osd_enable_gps (OSM_GPS_MAP(context->widget), 
-		 OSM_GPS_MAP_OSD_CALLBACK(ok?cb_map_gps:NULL), context);
+  if(ok != goto_is_enabled) {
+    osm_gps_map_osd_enable_gps (OSM_GPS_MAP(context->widget), 
+		OSM_GPS_MAP_OSD_CALLBACK(ok?cb_map_gps:NULL), context);
+    goto_is_enabled = ok;
+  }
 
   if(ok) {
     float heading = NAN;
@@ -131,6 +135,8 @@
 	radius = dist2pixel(context, eph/1000, refpos->lat);
     }
 
+    /* TODO: in order to save energy: only draw if state actually changed */
+
     g_object_set(context->widget, "gps-track-highlight-radius", radius, NULL);
     osm_gps_map_draw_gps(OSM_GPS_MAP(context->widget), 
 			 refpos->lat, refpos->lon, heading);