protected function addIconsConfig(ArrayNodeDefinition $rootNode)
    {
        $iconSets = ['glyphicons', 'fontawesome', 'fontawesome4'];

        $rootNode
            ->children()
                ->arrayNode('icons')
                    ->addDefaultsIfNotSet()
                    ->children()
                        ->scalarNode('icon_set')
                            ->info('Icon set to use: '.json_encode($iconSets))
                            ->defaultValue('glyphicons')
                            ->validate()
                                ->ifNotInArray($iconSets)
                                ->thenInvalid('Must choose one of '.json_encode($iconSets))
                            ->end()
                        ->end()
                        ->scalarNode('shortcut')
                            ->info('Alias for vic_mopa_bootstrap_icon()')
                            ->defaultValue('icon')
                        ->end()
                    ->end()
                ->end()
            ->end();
    }