// when the mouse is over a vertex, show the vertex's label
public void mouseMoved (MouseEvent me) {
Vertex vertex = vertexAt(me.getX(), me.getY());
if (vertex != null) {
if (statusLabel_ != null) {
AirportSpecs as = (AirportSpecs)vertex.element();
statusLabel_.setText(as.label());
}
}
else {
if (statusLabel_ != null) {
statusLabel_.setText("");