private void initViewer()
{
SchemaPool pool = SchemaPool.getInstance();
//we want to be notified if the pool has been modified
pool.addListener( this );
viewer = new TreeViewer( parent, SWT.MULTI | SWT.H_SCROLL | SWT.V_SCROLL | SWT.BORDER );
contentProvider = new HierarchicalContentProvider( pool );
contentProvider.bindToTreeViewer( viewer );
viewer.addDoubleClickListener( HierarchicalViewerController.getInstance() );