/**
 * filter to create one menu per language for dashboard
 * detect the default one created by theme ($menu_locations[0])
 * @since 0.9.7
 */
 
add_action ( 'init', 'xili_create_menu_locations',100 );
 
function xili_create_menu_locations () {
	$xili_theme_options = xili_twentyeleven_get_theme_options() ; 
	if ( $xili_theme_options['nav_menus'] == 'nav_menus' ) {  // ok for automatic insertion of one menu per lang...
		$menu_locations =  array_keys( get_nav_menu_locations()); 
		if ( class_exists('xili_language') ) {
			global $xili_language ;
			$default = 'en_us'; // currently the default language of theme in core WP
			$language_xili_settings = get_option('xili_language_settings');
			$language_slugs_list =  array_keys ( $language_xili_settings['langs_ids_array'] ) ;
			foreach ( $language_slugs_list as $slug ) {
				$one_menu_location = $menu_locations[0].'_'.$slug ;
				if ( $slug != $default && !isset($menu_locations[$one_menu_location]) ) {
					register_nav_menu ( $one_menu_location,  sprintf( __('Menu for %s','twentyeleven'), $slug ) );
				}
			}
		} 
	}
}

/**
 * filter to avoid modifying theme's header and changes 'virtually' location for each language
 * @since 0.9.7
 */
 
add_filter ( 'wp_nav_menu_args', 'xili_wp_nav_menu_args' ); // called at line #145 in nav-menu-template.php
 
function xili_wp_nav_menu_args ( $args ) {
	if ( class_exists('xili_language') ) {
		global $xili_language ;
		$default = 'en_us'; // currently the default language of theme as in core WP
		$slug = the_curlang();
		if ( $default != $slug ) {
			$theme_location = $args['theme_location'];
			if ( has_nav_menu ( $theme_location.'_'.$slug ) ) { // only if a menu is set by webmaster in menus dashboard
				$args['theme_location'] = $theme_location .'_'.$slug ;
			}	
		}
	}	
	return $args;
}