skilld_lang_dropdown.module

<?php

/**
 * @file
 * Primary module hooks for Language dropdown module.
 */

use Drupal\Core\Url;
use Drupal\Core\Template\Attribute;
use Drupal\Component\Serialization\Json;

/**
 * Implements hook_language_switch_links_alter().
 */
function skilld_lang_dropdown_language_switch_links_alter(
  array &$links,
  $type,
  Url $url
) {
  $is_error_page = \Drupal::request()->attributes->has('exception');
  $current_langcode = \Drupal::languageManager()
    ->getCurrentLanguage()
    ->getId();
  foreach ($links as $langcode => &$link) {
    if ($is_error_page) {
      $link['url'] = Url::fromRoute('<front>');
      $link['query'] = [];
    }
    if ($current_langcode === $langcode) {
      unset($link['url']);
      $link['attributes']['class'][] = 'is-active';
    }
  }

}

/**
 * Implements hook_theme().
 */
function skilld_lang_dropdown_theme($existing, $type, $theme, $path) {
  return [
    'dropdown_button' => [
      'template' => 'dropdown-button',
      'variables' => [
        'attributes' => [],
        'set_active_class' => FALSE,
        'links' => [],
        'button_icon' => '',
        'button_text' => '',
      ],
    ],
  ];
}

function template_preprocess_dropdown_button(&$variables) {
  $links = $variables['links'];
  if (!empty($links)) {
    $variables['links'] = [];
    foreach ($links as $key => $link) {
      $item = [];
      $link += [
        'ajax' => NULL,
        'url' => NULL,
      ];

      $li_attributes = new Attribute($link['attributes']);
      $keys = ['title', 'url'];

      $link_element = [
        '#type' => 'link',
        '#title' => $link['title'],
        '#options' => array_diff_key($link, array_combine($keys, $keys)),
        '#url' => $link['url'],
        '#ajax' => $link['ajax'],
      ];

      // Handle links and ensure that the active class is added on the LIs, but
      // only if the 'set_active_class' option is not empty. Links templates
      // duplicate the "is-active" class handling of l() and
      // LinkGenerator::generate() because they need to be able to set the
      // "is-active" class not on the links themselves (<a> tags), but on the
      // list items (<li> tags) that contain the links. This is necessary for
      // CSS to be able to style list items differently when the link is active,
      // since CSS does not yet allow one to style list items only if they
      // contain a certain element with a certain class. That is, we cannot yet
      // convert this jQuery selector to a CSS selector:
      // jQuery('li:has("a.is-active")')
      if (isset($link['url'])) {
        if (!empty($variables['set_active_class'])) {

          // Also enable set_active_class for the contained link.
          $link_element['#options']['set_active_class'] = TRUE;

          if (!empty($link['language'])) {
            $li_attributes['hreflang'] = $link['language']->getId();
          }

          // Add a "data-drupal-link-query" attribute to let the
          // drupal.active-link library know the query in a standardized manner.
          // Only add the data- attribute. The "is-active" class will be
          // calculated using JavaScript, to prevent breaking the render cache.
          if (!empty($link['query'])) {
            $query = $link['query'];
            ksort($query);
            $li_attributes['data-drupal-link-query'] = Json::encode($query);
          }

          /** @var \Drupal\Core\Url $url */
          $url = $link['url'];
          if ($url->isRouted()) {
            // Add a "data-drupal-link-system-path" attribute to let the
            // drupal.active-link library know the path in a standardized
            // manner. Only add the data- attribute. The "is-active" class will
            // be calculated using JavaScript, to prevent breaking the render
            // cache.
            $system_path = $url->getInternalPath();
            // @todo System path is deprecated - use the route name and parameters.
            // Special case for the front page.
            $li_attributes['data-drupal-link-system-path'] = $system_path == '' ? '<front>' : $system_path;
          }
        }

        $item['link'] = $link_element;
      }

      // Handle title-only text items.
      $item['text'] = $link['title'];
      if (isset($link['attributes'])) {
        $item['text_attributes'] = new Attribute($link['attributes']);
      }

      // Handle list item attributes.
      $item['attributes'] = new Attribute($li_attributes);

      // Add the item to the list of links.
      $variables['links'][$key] = $item;
    }
  }
}