panel.setLayout(new VerticalLayout());
if (allowExpressionBasedColumns) {
final JButton expressionColumnButton = WidgetFactory.createSmallButton(EXPRESSION_COLUMN_ICON_PATH);
expressionColumnButton.setToolTipText("Create expression/value based column");
expressionColumnButton.addActionListener(new AddExpressionBasedColumnActionListener(this));
expressionColumnButton.addMouseListener(buttonMouseListener);
panel.add(expressionColumnButton);
}
if (_propertyDescriptor.isArray()) {