Bug 200312 Chart Variables are still in the bottom right pane when select other categories [13]
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/ExpressionBuilder.java
} );
		treeViewer.addSelectionChangedListener( selectionListener );
		treeViewer.addDoubleClickListener( doubleClickListener );
	}
	private void initTable( TableViewer tableViewer )
	{
		final Table table = tableViewer.getTable( );
		GridData gd = new GridData( GridData.FILL_BOTH );
		gd.heightHint = 150;
		table.setLayoutData( gd );
		table.setToolTipText( null );
		new TableColumn( table, SWT.NONE ).setWidth( 200 );
		table.addMouseTrackListener( new MouseTrackAdapter( ) {
			public void mouseHover( MouseEvent event )
			{
				Widget widget = event.widget;
				if ( widget == table )
				{
					Point pt = new Point( event.x, event.y );
					TableItem item = table.getItem( pt );
					if ( item == null )
					{
						table.setToolTipText( null );
					}
					else
					{
						table.setToolTipText( provider.getTooltipText( item.getData( ) ) );
					}
				}
			}