edgeTransformerGroup = new ButtonGroup();
TransformerBuilder[] builders = Lookup.getDefault().lookupAll(TransformerBuilder.class).toArray(new TransformerBuilder[0]);
for (final TransformerBuilder t : builders) {
TransformerUI transformerUI = t.getUI();
JToggleButton btn = new JToggleButton(transformerUI.getIcon());
btn.setToolTipText(transformerUI.getName());
btn.setVisible(false);
btn.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
PartitionController pc = Lookup.getDefault().lookup(PartitionController.class);