diff -r 44897b1ba4e2 -r 15b51d278bf0 gui/graph_displayer_canvas-event.cc
--- a/gui/graph_displayer_canvas-event.cc	Wed Jul 27 11:19:35 2005 +0000
+++ b/gui/graph_displayer_canvas-event.cc	Wed Jul 27 11:35:13 2005 +0000
@@ -854,29 +854,46 @@
 
 }
 
-void GraphDisplayerCanvas::addNewEdgeMap(double default_value, std::string mapname)
+int GraphDisplayerCanvas::addNewEdgeMap(double default_value, std::string mapname)
 {
   //create the new map
   Graph::EdgeMap<double> * emptr=new Graph::EdgeMap<double> (g,default_value);
-  mapstorage.addEdgeMap(mapname,emptr);
+
+  //if addition was not successful addEdgeMap returns one.
+  //cause can be that there is already a map named like the new one
+  if(mapstorage.addEdgeMap(mapname,emptr))
+    {
+      return 1;
+    }
+
 
   //add it to the list of the displayable maps
   mapwin->registerNewEdgeMap(mapname);
 
   //display it
   changeEdgeText(mapname);
+
+  return 0;
 }
 
-void GraphDisplayerCanvas::addNewNodeMap(double default_value, std::string mapname)
+int GraphDisplayerCanvas::addNewNodeMap(double default_value, std::string mapname)
 {
   //create the new map
   Graph::NodeMap<double> * emptr=new Graph::NodeMap<double> (g,default_value);
-  mapstorage.addNodeMap(mapname,emptr);
+
+  //if addition was not successful addNodeMap returns one.
+  //cause can be that there is already a map named like the new one
+  if(mapstorage.addNodeMap(mapname,emptr))
+    {
+      return 1;
+    }
 
   //add it to the list of the displayable maps
   mapwin->registerNewNodeMap(mapname);
 
   //display it
   changeNodeText(mapname);
+
+  return 0;
 }