GridData gridData = new GridData( SWT.FILL, SWT.FILL, true, true );
gridData.heightHint = 250;
treeViewer.getTree().setLayoutData( gridData );
treeViewer.setContentProvider( new DifferencesWidgetSchemaContentProvider() );
treeViewer.setLabelProvider( new DifferencesWidgetSchemaLabelProvider() );
treeViewer.addSelectionChangedListener( new ISelectionChangedListener()
{
public void selectionChanged( SelectionChangedEvent event )
{
StructuredSelection selection = ( StructuredSelection ) event.getSelection();
Object element = selection.getFirstElement();