private void populateInputVariableComboBox() {
    inputVariableComboBox.setEnabled(false);

    inputVariableComboBox.setDecomposition(net.getNetModel().getDecomposition());

    if (inputVariableComboBox.getItemCount() > 0) {
      inputVariableComboBox.setEnabled(true);
      inputVariableQueryButton.setEnabled(true);
    } else {
      inputVariableComboBox.setEnabled(false);
      inputVariableQueryButton.setEnabled(false);
    }
  }
 public void actionPerformed(ActionEvent event) {
   final NetGraph graph = getGraph();
   if (graph != null) {
     NetCellUtilities.alignCellsAlongVerticalCentre(graph, graph.getSelectionCells());
   }
 }