theme.inc

<?php


/**
 * @file
 * The theme system, which controls the output of Drupal.
 *
 * The theme system allows for nearly all output of the Drupal system to be
 * customized by user themes.
 */
use Drupal\Core\Url;
use Drupal\Component\Serialization\Json;
use Drupal\Component\Utility\Crypt;
use Drupal\Component\Utility\Html;
use Drupal\Component\Render\MarkupInterface;
use Drupal\Core\Cache\CacheableDependencyInterface;
use Drupal\Core\Config\Config;
use Drupal\Core\Config\StorageException;
use Drupal\Core\Render\AttachmentsInterface;
use Drupal\Core\Render\BubbleableMetadata;
use Drupal\Core\Render\RenderableInterface;
use Drupal\Core\Template\Attribute;
use Drupal\Core\Template\AttributeHelper;
use Drupal\Core\Theme\ThemeSettings;
use Drupal\Core\Render\Element;
use Drupal\Core\Render\Markup;
use Drupal\Core\Utility\TableSort;

/**
 * @defgroup content_flags Content markers
 * @{
 * Markers used by mark.html.twig and node_mark() to designate content.
 *
 * @see mark.html.twig
 * @see node_mark()
 */

/**
 * Mark content as read.
 */
const MARK_READ = 0;

/**
 * Mark content as being new.
 */
const MARK_NEW = 1;

/**
 * Mark content as being updated.
 */
const MARK_UPDATED = 2;

/**
 * A responsive table class; hide table cell on narrow devices.
 *
 * Indicates that a column has medium priority and thus can be hidden on narrow
 * width devices and shown on medium+ width devices (i.e. tablets and desktops).
 */
const RESPONSIVE_PRIORITY_MEDIUM = 'priority-medium';

/**
 * A responsive table class; only show table cell on wide devices.
 *
 * Indicates that a column has low priority and thus can be hidden on narrow
 * and medium viewports and shown on wide devices (i.e. desktops).
 */
const RESPONSIVE_PRIORITY_LOW = 'priority-low';

/**
 * @} End of "defgroup content_flags".
 */

/**
 * Gets the theme registry.
 *
 * @param bool $complete
 *   Optional boolean to indicate whether to return the complete theme registry
 *   array or an instance of the Drupal\Core\Utility\ThemeRegistry class.
 *   If TRUE, the complete theme registry array will be returned. This is useful
 *   if you want to foreach over the whole registry, use array_* functions or
 *   inspect it in a debugger. If FALSE, an instance of the
 *   Drupal\Core\Utility\ThemeRegistry class will be returned, this provides an
 *   ArrayObject which allows it to be accessed with array syntax and isset(),
 *   and should be more lightweight than the full registry. Defaults to TRUE.
 *
 * @return
 *   The complete theme registry array, or an instance of the
 *   Drupal\Core\Utility\ThemeRegistry class.
 */
function theme_get_registry($complete = TRUE) {
    $theme_registry = \Drupal::service('theme.registry');
    if ($complete) {
        return $theme_registry->get();
    }
    else {
        return $theme_registry->getRuntime();
    }
}

/**
 * Returns an array of default theme features.
 *
 * @see \Drupal\Core\Extension\ThemeExtensionList::$defaults
 */
function _system_default_theme_features() {
    return [
        'favicon',
        'logo',
        'node_user_picture',
        'comment_user_picture',
        'comment_user_verification',
    ];
}

/**
 * Forces the system to rebuild the theme registry.
 *
 * This function should be called when modules are added to the system, or when
 * a dynamic system needs to add more theme hooks.
 */
function drupal_theme_rebuild() {
    \Drupal::service('theme.registry')->reset();
}

/**
 * Allows themes and/or theme engines to discover overridden theme functions.
 *
 * @param array $cache
 *   The existing cache of theme hooks to test against.
 * @param array $prefixes
 *   An array of prefixes to test, in reverse order of importance.
 *
 * @return array
 *   The functions found, suitable for returning from hook_theme;
 */
function drupal_find_theme_functions($cache, $prefixes) {
    $implementations = [];
    $grouped_functions = \Drupal::service('theme.registry')->getPrefixGroupedUserFunctions($prefixes);
    foreach ($cache as $hook => $info) {
        foreach ($prefixes as $prefix) {
            // Find theme functions that implement possible "suggestion" variants of
            // registered theme hooks and add those as new registered theme hooks.
            // The 'pattern' key defines a common prefix that all suggestions must
            // start with. The default is the name of the hook followed by '__'. An
            // 'base hook' key is added to each entry made for a found suggestion,
            // so that common functionality can be implemented for all suggestions of
            // the same base hook. To keep things simple, deep hierarchy of
            // suggestions is not supported: each suggestion's 'base hook' key
            // refers to a base hook, not to another suggestion, and all suggestions
            // are found using the base hook's pattern, not a pattern from an
            // intermediary suggestion.
            $pattern = isset($info['pattern']) ? $info['pattern'] : $hook . '__';
            // Grep only the functions which are within the prefix group.
            list($first_prefix, ) = explode('_', $prefix, 2);
            if (!isset($info['base hook']) && !empty($pattern) && isset($grouped_functions[$first_prefix])) {
                $matches = preg_grep('/^' . $prefix . '_' . $pattern . '/', $grouped_functions[$first_prefix]);
                if ($matches) {
                    foreach ($matches as $match) {
                        $new_hook = substr($match, strlen($prefix) + 1);
                        $arg_name = isset($info['variables']) ? 'variables' : 'render element';
                        $implementations[$new_hook] = [
                            'function' => $match,
                            $arg_name => $info[$arg_name],
                            'base hook' => $hook,
                        ];
                    }
                }
            }
            // Find theme functions that implement registered theme hooks and include
            // that in what is returned so that the registry knows that the theme has
            // this implementation.
            if (function_exists($prefix . '_' . $hook)) {
                $implementations[$hook] = [
                    'function' => $prefix . '_' . $hook,
                ];
            }
        }
    }
    return $implementations;
}

/**
 * Allows themes and/or theme engines to easily discover overridden templates.
 *
 * @param $cache
 *   The existing cache of theme hooks to test against.
 * @param $extension
 *   The extension that these templates will have.
 * @param $path
 *   The path to search.
 */
function drupal_find_theme_templates($cache, $extension, $path) {
    $implementations = [];
    // Collect paths to all sub-themes grouped by base themes. These will be
    // used for filtering. This allows base themes to have sub-themes in its
    // folder hierarchy without affecting the base themes template discovery.
    $theme_paths = [];
    foreach (\Drupal::service('theme_handler')->listInfo() as $theme_info) {
        if (!empty($theme_info->base_theme)) {
            $theme_paths[$theme_info->base_theme][$theme_info->getName()] = $theme_info->getPath();
        }
    }
    foreach ($theme_paths as $basetheme => $subthemes) {
        foreach ($subthemes as $subtheme => $subtheme_path) {
            if (isset($theme_paths[$subtheme])) {
                $theme_paths[$basetheme] = array_merge($theme_paths[$basetheme], $theme_paths[$subtheme]);
            }
        }
    }
    $theme = \Drupal::theme()->getActiveTheme()
        ->getName();
    $subtheme_paths = isset($theme_paths[$theme]) ? $theme_paths[$theme] : [];
    // Escape the periods in the extension.
    $regex = '/' . str_replace('.', '\\.', $extension) . '$/';
    // Get a listing of all template files in the path to search.
    $files = [];
    if (is_dir($path)) {
        $files = \Drupal::service('file_system')->scanDirectory($path, $regex, [
            'key' => 'filename',
        ]);
    }
    // Find templates that implement registered theme hooks and include that in
    // what is returned so that the registry knows that the theme has this
    // implementation.
    foreach ($files as $template => $file) {
        // Ignore sub-theme templates for the current theme.
        if (strpos($file->uri, str_replace($subtheme_paths, '', $file->uri)) !== 0) {
            continue;
        }
        // Remove the extension from the filename.
        $template = str_replace($extension, '', $template);
        // Transform - in filenames to _ to match function naming scheme
        // for the purposes of searching.
        $hook = strtr($template, '-', '_');
        if (isset($cache[$hook])) {
            $implementations[$hook] = [
                'template' => $template,
                'path' => dirname($file->uri),
            ];
        }
        // Match templates based on the 'template' filename.
        foreach ($cache as $hook => $info) {
            if (isset($info['template'])) {
                if ($template === $info['template']) {
                    $implementations[$hook] = [
                        'template' => $template,
                        'path' => dirname($file->uri),
                    ];
                }
            }
        }
    }
    // Find templates that implement possible "suggestion" variants of registered
    // theme hooks and add those as new registered theme hooks. See
    // drupal_find_theme_functions() for more information about suggestions and
    // the use of 'pattern' and 'base hook'.
    $patterns = array_keys($files);
    foreach ($cache as $hook => $info) {
        $pattern = isset($info['pattern']) ? $info['pattern'] : $hook . '__';
        if (!isset($info['base hook']) && !empty($pattern)) {
            // Transform _ in pattern to - to match file naming scheme
            // for the purposes of searching.
            $pattern = strtr($pattern, '_', '-');
            $matches = preg_grep('/^' . $pattern . '/', $patterns);
            if ($matches) {
                foreach ($matches as $match) {
                    $file = $match;
                    // Remove the extension from the filename.
                    $file = str_replace($extension, '', $file);
                    // Put the underscores back in for the hook name and register this
                    // pattern.
                    $arg_name = isset($info['variables']) ? 'variables' : 'render element';
                    $implementations[strtr($file, '-', '_')] = [
                        'template' => $file,
                        'path' => dirname($files[$match]->uri),
                        $arg_name => $info[$arg_name],
                        'base hook' => $hook,
                    ];
                }
            }
        }
    }
    return $implementations;
}

/**
 * Retrieves a setting for the current theme or for a given theme.
 *
 * The final setting is obtained from the last value found in the following
 * sources:
 * - the saved values from the global theme settings form
 * - the saved values from the theme's settings form
 * To only retrieve the default global theme setting, an empty string should be
 * given for $theme.
 *
 * @param $setting_name
 *   The name of the setting to be retrieved.
 * @param $theme
 *   The name of a given theme; defaults to the current theme.
 *
 * @return
 *   The value of the requested setting, NULL if the setting does not exist.
 */
function theme_get_setting($setting_name, $theme = NULL) {
    
    /** @var \Drupal\Core\Theme\ThemeSettings[] $cache */
    $cache =& drupal_static(__FUNCTION__, []);
    // If no key is given, use the current theme if we can determine it.
    if (!isset($theme)) {
        $theme = \Drupal::theme()->getActiveTheme()
            ->getName();
    }
    if (empty($cache[$theme])) {
        // Create a theme settings object.
        $cache[$theme] = new ThemeSettings($theme);
        // Get the global settings from configuration.
        $cache[$theme]->setData(\Drupal::config('system.theme.global')->get());
        // Get the values for the theme-specific settings from the .info.yml files
        // of the theme and all its base themes.
        $themes = \Drupal::service('theme_handler')->listInfo();
        if (isset($themes[$theme])) {
            $theme_object = $themes[$theme];
            // Retrieve configured theme-specific settings, if any.
            try {
                if ($theme_settings = \Drupal::config($theme . '.settings')->get()) {
                    $cache[$theme]->merge($theme_settings);
                }
            } catch (StorageException $e) {
            }
            // If the theme does not support a particular feature, override the global
            // setting and set the value to NULL.
            if (!empty($theme_object->info['features'])) {
                foreach (_system_default_theme_features() as $feature) {
                    if (!in_array($feature, $theme_object->info['features'])) {
                        $cache[$theme]->set('features.' . $feature, NULL);
                    }
                }
            }
            // Generate the path to the logo image.
            if ($cache[$theme]->get('logo.use_default')) {
                $logo = \Drupal::service('theme.initialization')->getActiveThemeByName($theme)
                    ->getLogo();
                $cache[$theme]->set('logo.url', file_url_transform_relative(file_create_url($logo)));
            }
            elseif ($logo_path = $cache[$theme]->get('logo.path')) {
                $cache[$theme]->set('logo.url', file_url_transform_relative(file_create_url($logo_path)));
            }
            // Generate the path to the favicon.
            if ($cache[$theme]->get('features.favicon')) {
                $favicon_path = $cache[$theme]->get('favicon.path');
                if ($cache[$theme]->get('favicon.use_default')) {
                    if (file_exists($favicon = $theme_object->getPath() . '/favicon.ico')) {
                        $cache[$theme]->set('favicon.url', file_url_transform_relative(file_create_url($favicon)));
                    }
                    else {
                        $cache[$theme]->set('favicon.url', file_url_transform_relative(file_create_url('core/misc/favicon.ico')));
                    }
                }
                elseif ($favicon_path) {
                    $cache[$theme]->set('favicon.url', file_url_transform_relative(file_create_url($favicon_path)));
                }
                else {
                    $cache[$theme]->set('features.favicon', FALSE);
                }
            }
        }
    }
    return $cache[$theme]->get($setting_name);
}

/**
 * Escapes and renders variables for theme functions.
 *
 * This method is used in theme functions to ensure that the result is safe for
 * output inside HTML fragments. This mimics the behavior of the auto-escape
 * functionality in Twig.
 *
 * Note: This function should be kept in sync with
 * \Drupal\Core\Template\TwigExtension::escapeFilter().
 *
 * @param mixed $arg
 *   The string, object, or render array to escape if needed.
 *
 * @return string
 *   The rendered string, safe for use in HTML. The string is not safe when used
 *   as any part of an HTML attribute name or value.
 *
 * @throws \Exception
 *   Thrown when an object is passed in which cannot be printed.
 *
 * @see \Drupal\Core\Template\TwigExtension::escapeFilter()
 *
 * @todo Discuss deprecating this in https://www.drupal.org/node/2575081.
 * @todo Refactor this to keep it in sync with Twig filtering in
 *   https://www.drupal.org/node/2575065
 */
function theme_render_and_autoescape($arg) {
    // If it's a renderable, then it'll be up to the generated render array it
    // returns to contain the necessary cacheability & attachment metadata. If
    // it doesn't implement CacheableDependencyInterface or AttachmentsInterface
    // then there is nothing to do here.
    if (!$arg instanceof RenderableInterface && ($arg instanceof CacheableDependencyInterface || $arg instanceof AttachmentsInterface)) {
        $arg_bubbleable = [];
        BubbleableMetadata::createFromObject($arg)->applyTo($arg_bubbleable);
        \Drupal::service('renderer')->render($arg_bubbleable);
    }
    if ($arg instanceof MarkupInterface) {
        return (string) $arg;
    }
    $return = NULL;
    if (is_scalar($arg)) {
        $return = (string) $arg;
    }
    elseif (is_object($arg)) {
        if ($arg instanceof RenderableInterface) {
            $arg = $arg->toRenderable();
        }
        elseif (method_exists($arg, '__toString')) {
            $return = (string) $arg;
        }
        elseif (method_exists($arg, 'toString')) {
            $return = $arg->toString();
        }
        else {
            throw new \Exception('Object of type ' . get_class($arg) . ' cannot be printed.');
        }
    }
    // We have a string or an object converted to a string: Escape it!
    if (isset($return)) {
        return $return instanceof MarkupInterface ? $return : Html::escape($return);
    }
    // This is a normal render array, which is safe by definition, with special
    // simple cases already handled.
    // Early return if this element was pre-rendered (no need to re-render).
    if (isset($arg['#printed']) && $arg['#printed'] == TRUE && isset($arg['#markup']) && strlen($arg['#markup']) > 0) {
        return (string) $arg['#markup'];
    }
    $arg['#printed'] = FALSE;
    return (string) \Drupal::service('renderer')->render($arg);
}

/**
 * Converts theme settings to configuration.
 *
 * @see system_theme_settings_submit()
 *
 * @param array $theme_settings
 *   An array of theme settings from system setting form or a Drupal 7 variable.
 * @param \Drupal\Core\Config\Config $config
 *   The configuration object to update.
 *
 * @return
 *   The Config object with updated data.
 */
function theme_settings_convert_to_config(array $theme_settings, Config $config) {
    foreach ($theme_settings as $key => $value) {
        if ($key == 'default_logo') {
            $config->set('logo.use_default', $value);
        }
        elseif ($key == 'logo_path') {
            $config->set('logo.path', $value);
        }
        elseif ($key == 'default_favicon') {
            $config->set('favicon.use_default', $value);
        }
        elseif ($key == 'favicon_path') {
            $config->set('favicon.path', $value);
        }
        elseif ($key == 'favicon_mimetype') {
            $config->set('favicon.mimetype', $value);
        }
        elseif (substr($key, 0, 7) == 'toggle_') {
            $config->set('features.' . mb_substr($key, 7), $value);
        }
        elseif (!in_array($key, [
            'theme',
            'logo_upload',
        ])) {
            $config->set($key, $value);
        }
    }
    return $config;
}

/**
 * Prepares variables for time templates.
 *
 * Default template: time.html.twig.
 *
 * @param array $variables
 *   An associative array possibly containing:
 *   - attributes['timestamp']:
 *   - timestamp:
 *   - text:
 */
function template_preprocess_time(&$variables) {
    
    /** @var \Drupal\Core\Datetime\DateFormatterInterface $date_formatter */
    $date_formatter = \Drupal::service('date.formatter');
    // Format the 'datetime' attribute based on the timestamp.
    // @see http://www.w3.org/TR/html5-author/the-time-element.html#attr-time-datetime
    if (!isset($variables['attributes']['datetime']) && isset($variables['timestamp'])) {
        $variables['attributes']['datetime'] = $date_formatter->format($variables['timestamp'], 'html_datetime', '', 'UTC');
    }
    // If no text was provided, try to auto-generate it.
    if (!isset($variables['text'])) {
        // Format and use a human-readable version of the timestamp, if any.
        if (isset($variables['timestamp'])) {
            $variables['text'] = $date_formatter->format($variables['timestamp']);
        }
        elseif (isset($variables['attributes']['datetime'])) {
            $variables['text'] = $variables['attributes']['datetime'];
        }
    }
}

/**
 * Prepares variables for datetime form element templates.
 *
 * The datetime form element serves as a wrapper around the date element type,
 * which creates a date and a time component for a date.
 *
 * Default template: datetime-form.html.twig.
 *
 * @param array $variables
 *   An associative array containing:
 *   - element: An associative array containing the properties of the element.
 *     Properties used: #title, #value, #options, #description, #required,
 *     #attributes.
 *
 * @see form_process_datetime()
 */
function template_preprocess_datetime_form(&$variables) {
    $element = $variables['element'];
    $variables['attributes'] = [];
    if (isset($element['#id'])) {
        $variables['attributes']['id'] = $element['#id'];
    }
    if (!empty($element['#attributes']['class'])) {
        $variables['attributes']['class'] = (array) $element['#attributes']['class'];
    }
    $variables['content'] = $element;
}

/**
 * Prepares variables for datetime form wrapper templates.
 *
 * Default template: datetime-wrapper.html.twig.
 *
 * @param array $variables
 *   An associative array containing:
 *   - element: An associative array containing the properties of the element.
 *     Properties used: #title, #children, #required, #attributes.
 */
function template_preprocess_datetime_wrapper(&$variables) {
    $element = $variables['element'];
    if (!empty($element['#title'])) {
        $variables['title'] = $element['#title'];
        // If the element title is a string, wrap it a render array so that markup
        // will not be escaped (but XSS-filtered).
        if (is_string($variables['title']) && $variables['title'] !== '') {
            $variables['title'] = [
                '#markup' => $variables['title'],
            ];
        }
    }
    // Suppress error messages.
    $variables['errors'] = NULL;
    $variables['description'] = NULL;
    if (!empty($element['#description'])) {
        $description_attributes = [];
        if (!empty($element['#id'])) {
            $description_attributes['id'] = $element['#id'] . '--description';
        }
        $variables['description'] = $element['#description'];
        $variables['description_attributes'] = new Attribute($description_attributes);
    }
    $variables['required'] = FALSE;
    // For required datetime fields 'form-required' & 'js-form-required' classes
    // are appended to the label attributes.
    if (!empty($element['#required'])) {
        $variables['required'] = TRUE;
    }
    $variables['content'] = $element['#children'];
}

/**
 * Prepares variables for links templates.
 *
 * Default template: links.html.twig.
 *
 * Unfortunately links templates duplicate the "active" class handling of l()
 * and LinkGenerator::generate() because it needs to be able to set the "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 it contains a certain element with a certain
 * class. I.e. we cannot yet convert this jQuery selector to a CSS selector:
 * jQuery('li:has("a.is-active")')
 *
 * @param array $variables
 *   An associative array containing:
 *   - links: An array of links to be themed. Each link itself is an array, with
 *     the following elements:
 *     - title: The link text.
 *     - url: (optional) The \Drupal\Core\Url object to link to. If the 'url'
 *       element is supplied, the 'title' and 'url' are used to generate a link
 *       through \Drupal::linkGenerator()->generate(). All data from the link
 *       array other than 'title' and 'url' are added as #options on
 *       the URL object. See \Drupal\Core\Url::fromUri() for details on the
 *       options. If no 'url' is supplied, the 'title' is printed as plain text.
 *     - attributes: (optional) Attributes for the anchor, or for the <span>
 *       tag used in its place if no 'url' is supplied. If element 'class' is
 *       included, it must be an array of one or more class names.
 *   - attributes: A keyed array of attributes for the <ul> containing the list
 *     of links.
 *   - set_active_class: (optional) Whether each link should compare the
 *     route_name + route_parameters or url (path), language, and query options
 *     to the current URL, to determine whether the link is "active". If so,
 *     attributes will be added to the HTML elements for both the link and the
 *     list item that contains it, which will result in an "is-active" class
 *     being added to both. The class is added via JavaScript for authenticated
 *     users (in the active-link library), and via PHP for anonymous users (in
 *     the \Drupal\Core\EventSubscriber\ActiveLinkResponseFilter class).
 *   - heading: (optional) A heading to precede the links. May be an
 *     associative array or a string. If it's an array, it can have the
 *     following elements:
 *     - text: The heading text.
 *     - level: The heading level (e.g. 'h2', 'h3').
 *     - attributes: (optional) An array of the CSS attributes for the heading.
 *     When using a string it will be used as the text of the heading and the
 *     level will default to 'h2'. Headings should be used on navigation menus
 *     and any list of links that consistently appears on multiple pages. To
 *     make the heading invisible use the 'visually-hidden' CSS class. Do not
 *     use 'display:none', which removes it from screen readers and assistive
 *     technology. Headings allow screen reader and keyboard only users to
 *     navigate to or skip the links. See
 *     http://juicystudio.com/article/screen-readers-display-none.php and
 *     http://www.w3.org/TR/WCAG-TECHS/H42.html for more information.
 *
 * @see \Drupal\Core\Utility\LinkGenerator
 * @see \Drupal\Core\Utility\LinkGenerator::generate()
 * @see system_page_attachments()
 */
function template_preprocess_links(&$variables) {
    $links = $variables['links'];
    $heading =& $variables['heading'];
    if (!empty($links)) {
        // Prepend the heading to the list, if any.
        if (!empty($heading)) {
            // Convert a string heading into an array, using a <h2> tag by default.
            if (is_string($heading)) {
                $heading = [
                    'text' => $heading,
                ];
            }
            // Merge in default array properties into $heading.
            $heading += [
                'level' => 'h2',
                'attributes' => [],
            ];
            // Convert the attributes array into an Attribute object.
            $heading['attributes'] = new Attribute($heading['attributes']);
        }
        $variables['links'] = [];
        foreach ($links as $key => $link) {
            $item = [];
            $link += [
                'ajax' => NULL,
                'url' => NULL,
            ];
            $li_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;
        }
    }
}

/**
 * Prepares variables for image templates.
 *
 * Default template: image.html.twig.
 *
 * @param array $variables
 *   An associative array containing:
 *   - uri: Either the path of the image file (relative to base_path()) or a
 *     full URL.
 *   - width: The width of the image (if known).
 *   - height: The height of the image (if known).
 *   - alt: The alternative text for text-based browsers. HTML 4 and XHTML 1.0
 *     always require an alt attribute. The HTML 5 draft allows the alt
 *     attribute to be omitted in some cases. Therefore, this variable defaults
 *     to an empty string, but can be set to NULL for the attribute to be
 *     omitted. Usually, neither omission nor an empty string satisfies
 *     accessibility requirements, so it is strongly encouraged for code
 *     building variables for image.html.twig templates to pass a meaningful
 *     value for this variable.
 *     - http://www.w3.org/TR/REC-html40/struct/objects.html#h-13.8
 *     - http://www.w3.org/TR/xhtml1/dtds.html
 *     - http://dev.w3.org/html5/spec/Overview.html#alt
 *   - title: The title text is displayed when the image is hovered in some
 *     popular browsers.
 *   - attributes: Associative array of attributes to be placed in the img tag.
 *   - srcset: Array of multiple URIs and sizes/multipliers.
 *   - sizes: The sizes attribute for viewport-based selection of images.
 *     - http://www.whatwg.org/specs/web-apps/current-work/multipage/embedded-content.html#introduction-3:viewport-based-selection-2
 */
function template_preprocess_image(&$variables) {
    if (!empty($variables['uri'])) {
        $variables['attributes']['src'] = file_url_transform_relative(file_create_url($variables['uri']));
    }
    // Generate a srcset attribute conforming to the spec at
    // http://www.w3.org/html/wg/drafts/html/master/embedded-content.html#attr-img-srcset
    if (!empty($variables['srcset'])) {
        $srcset = [];
        foreach ($variables['srcset'] as $src) {
            // URI is mandatory.
            $source = file_url_transform_relative(file_create_url($src['uri']));
            if (isset($src['width']) && !empty($src['width'])) {
                $source .= ' ' . $src['width'];
            }
            elseif (isset($src['multiplier']) && !empty($src['multiplier'])) {
                $source .= ' ' . $src['multiplier'];
            }
            $srcset[] = $source;
        }
        $variables['attributes']['srcset'] = implode(', ', $srcset);
    }
    foreach ([
        'width',
        'height',
        'alt',
        'title',
        'sizes',
    ] as $key) {
        if (isset($variables[$key])) {
            // If the property has already been defined in the attributes,
            // do not override, including NULL.
            if (AttributeHelper::attributeExists($key, $variables['attributes'])) {
                continue;
            }
            $variables['attributes'][$key] = $variables[$key];
        }
    }
}

/**
 * Prepares variables for table templates.
 *
 * Default template: table.html.twig.
 *
 * @param array $variables
 *   An associative array containing:
 *   - header: An array containing the table headers. Each element of the array
 *     can be either a localized string or an associative array with the
 *     following keys:
 *     - data: The localized title of the table column, as a string or render
 *       array.
 *     - field: The database field represented in the table column (required
 *       if user is to be able to sort on this column).
 *     - sort: A default sort order for this column ("asc" or "desc"). Only
 *       one column should be given a default sort order because table sorting
 *       only applies to one column at a time.
 *     - initial_click_sort: Set the initial sort of the column when clicked.
 *       Defaults to "asc".
 *     - class: An array of values for the 'class' attribute. In particular,
 *       the least important columns that can be hidden on narrow and medium
 *       width screens should have a 'priority-low' class, referenced with the
 *       RESPONSIVE_PRIORITY_LOW constant. Columns that should be shown on
 *       medium+ wide screens should be marked up with a class of
 *       'priority-medium', referenced by with the RESPONSIVE_PRIORITY_MEDIUM
 *       constant. Themes may hide columns with one of these two classes on
 *       narrow viewports to save horizontal space.
 *     - Any HTML attributes, such as "colspan", to apply to the column header
 *       cell.
 *   - rows: An array of table rows. Every row is an array of cells, or an
 *     associative array with the following keys:
 *     - data: An array of cells.
 *     - Any HTML attributes, such as "class", to apply to the table row.
 *     - no_striping: A Boolean indicating that the row should receive no
 *       'even / odd' styling. Defaults to FALSE.
 *     Each cell can be either a string or an associative array with the
 *     following keys:
 *     - data: The string or render array to display in the table cell.
 *     - header: Indicates this cell is a header.
 *     - Any HTML attributes, such as "colspan", to apply to the table cell.
 *     Here's an example for $rows:
 *     @code
 *     $rows = array(
 *       // Simple row
 *       array(
 *         'Cell 1', 'Cell 2', 'Cell 3'
 *       ),
 *       // Row with attributes on the row and some of its cells.
 *       array(
 *         'data' => array('Cell 1', array('data' => 'Cell 2', 'colspan' => 2)), 'class' => array('funky')
 *       ),
 *     );
 *     @endcode
 *   - footer: An array of table rows which will be printed within a <tfoot>
 *     tag, in the same format as the rows element (see above).
 *   - attributes: An array of HTML attributes to apply to the table tag.
 *   - caption: A localized string to use for the <caption> tag.
 *   - colgroups: An array of column groups. Each element of the array can be
 *     either:
 *     - An array of columns, each of which is an associative array of HTML
 *       attributes applied to the <col> element.
 *     - An array of attributes applied to the <colgroup> element, which must
 *       include a "data" attribute. To add attributes to <col> elements,
 *       set the "data" attribute with an array of columns, each of which is an
 *       associative array of HTML attributes.
 *     Here's an example for $colgroup:
 *     @code
 *     $colgroup = array(
 *       // <colgroup> with one <col> element.
 *       array(
 *         array(
 *           'class' => array('funky'), // Attribute for the <col> element.
 *         ),
 *       ),
 *       // <colgroup> with attributes and inner <col> elements.
 *       array(
 *         'data' => array(
 *           array(
 *             'class' => array('funky'), // Attribute for the <col> element.
 *           ),
 *         ),
 *         'class' => array('jazzy'), // Attribute for the <colgroup> element.
 *       ),
 *     );
 *     @endcode
 *     These optional tags are used to group and set properties on columns
 *     within a table. For example, one may easily group three columns and
 *     apply same background style to all.
 *   - sticky: Use a "sticky" table header.
 *   - empty: The message to display in an extra row if table does not have any
 *     rows.
 */
function template_preprocess_table(&$variables) {
    // Format the table columns:
    if (!empty($variables['colgroups'])) {
        foreach ($variables['colgroups'] as &$colgroup) {
            // Check if we're dealing with a simple or complex column
            if (isset($colgroup['data'])) {
                $cols = $colgroup['data'];
                unset($colgroup['data']);
                $colgroup_attributes = $colgroup;
            }
            else {
                $cols = $colgroup;
                $colgroup_attributes = [];
            }
            $colgroup = [];
            $colgroup['attributes'] = new Attribute($colgroup_attributes);
            $colgroup['cols'] = [];
            // Build columns.
            if (is_array($cols) && !empty($cols)) {
                foreach ($cols as $col_key => $col) {
                    $colgroup['cols'][$col_key]['attributes'] = new Attribute($col);
                }
            }
        }
    }
    // Build an associative array of responsive classes keyed by column.
    $responsive_classes = [];
    // Format the table header:
    $ts = [];
    $header_columns = 0;
    if (!empty($variables['header'])) {
        $ts = TableSort::getContextFromRequest($variables['header'], \Drupal::request());
        // Use a separate index with responsive classes as headers
        // may be associative.
        $responsive_index = -1;
        foreach ($variables['header'] as $col_key => $cell) {
            // Increase the responsive index.
            $responsive_index++;
            if (!is_array($cell)) {
                $header_columns++;
                $cell_content = $cell;
                $cell_attributes = new Attribute();
                $is_header = TRUE;
            }
            else {
                if (isset($cell['colspan'])) {
                    $header_columns += $cell['colspan'];
                }
                else {
                    $header_columns++;
                }
                $cell_content = '';
                if (isset($cell['data'])) {
                    $cell_content = $cell['data'];
                    unset($cell['data']);
                }
                // Flag the cell as a header or not and remove the flag.
                $is_header = isset($cell['header']) ? $cell['header'] : TRUE;
                unset($cell['header']);
                // Track responsive classes for each column as needed. Only the header
                // cells for a column are marked up with the responsive classes by a
                // module developer or themer. The responsive classes on the header cells
                // must be transferred to the content cells.
                if (!empty($cell['class']) && is_array($cell['class'])) {
                    if (in_array(RESPONSIVE_PRIORITY_MEDIUM, $cell['class'])) {
                        $responsive_classes[$responsive_index] = RESPONSIVE_PRIORITY_MEDIUM;
                    }
                    elseif (in_array(RESPONSIVE_PRIORITY_LOW, $cell['class'])) {
                        $responsive_classes[$responsive_index] = RESPONSIVE_PRIORITY_LOW;
                    }
                }
                TableSort::header($cell_content, $cell, $variables['header'], $ts);
                // TableSort::header() removes the 'sort', 'initial_click_sort' and
                // 'field' keys.
                $cell_attributes = new Attribute($cell);
            }
            $variables['header'][$col_key] = [];
            $variables['header'][$col_key]['tag'] = $is_header ? 'th' : 'td';
            $variables['header'][$col_key]['attributes'] = $cell_attributes;
            $variables['header'][$col_key]['content'] = $cell_content;
        }
    }
    $variables['header_columns'] = $header_columns;
    // Rows and footer have the same structure.
    $sections = [
        'rows',
        'footer',
    ];
    foreach ($sections as $section) {
        if (!empty($variables[$section])) {
            foreach ($variables[$section] as $row_key => $row) {
                $cells = $row;
                $row_attributes = [];
                // Check if we're dealing with a simple or complex row
                if (isset($row['data'])) {
                    $cells = $row['data'];
                    $variables['no_striping'] = isset($row['no_striping']) ? $row['no_striping'] : FALSE;
                    // Set the attributes array and exclude 'data' and 'no_striping'.
                    $row_attributes = $row;
                    unset($row_attributes['data']);
                    unset($row_attributes['no_striping']);
                }
                // Build row.
                $variables[$section][$row_key] = [];
                $variables[$section][$row_key]['attributes'] = new Attribute($row_attributes);
                $variables[$section][$row_key]['cells'] = [];
                if (!empty($cells)) {
                    // Reset the responsive index.
                    $responsive_index = -1;
                    foreach ($cells as $col_key => $cell) {
                        // Increase the responsive index.
                        $responsive_index++;
                        if (!is_array($cell)) {
                            $cell_content = $cell;
                            $cell_attributes = [];
                            $is_header = FALSE;
                        }
                        else {
                            $cell_content = '';
                            if (isset($cell['data'])) {
                                $cell_content = $cell['data'];
                                unset($cell['data']);
                            }
                            // Flag the cell as a header or not and remove the flag.
                            $is_header = !empty($cell['header']);
                            unset($cell['header']);
                            $cell_attributes = $cell;
                        }
                        // Active table sort information.
                        if (isset($variables['header'][$col_key]['data']) && $variables['header'][$col_key]['data'] == $ts['name'] && !empty($variables['header'][$col_key]['field'])) {
                            $variables[$section][$row_key]['cells'][$col_key]['active_table_sort'] = TRUE;
                        }
                        // Copy RESPONSIVE_PRIORITY_LOW/RESPONSIVE_PRIORITY_MEDIUM
                        // class from header to cell as needed.
                        if (isset($responsive_classes[$responsive_index])) {
                            $cell_attributes['class'][] = $responsive_classes[$responsive_index];
                        }
                        $variables[$section][$row_key]['cells'][$col_key]['tag'] = $is_header ? 'th' : 'td';
                        $variables[$section][$row_key]['cells'][$col_key]['attributes'] = new Attribute($cell_attributes);
                        $variables[$section][$row_key]['cells'][$col_key]['content'] = $cell_content;
                    }
                }
            }
        }
    }
    if (empty($variables['no_striping'])) {
        $variables['attributes']['data-striping'] = 1;
    }
}

/**
 * Prepares variables for item list templates.
 *
 * Default template: item-list.html.twig.
 *
 * @param array $variables
 *   An associative array containing:
 *   - items: An array of items to be displayed in the list. Each item can be
 *     either a string or a render array. If #type, #theme, or #markup
 *     properties are not specified for child render arrays, they will be
 *     inherited from the parent list, allowing callers to specify larger
 *     nested lists without having to explicitly specify and repeat the
 *     render properties for all nested child lists.
 *   - title: A title to be prepended to the list.
 *   - list_type: The type of list to return (e.g. "ul", "ol").
 *   - wrapper_attributes: HTML attributes to be applied to the list wrapper.
 *
 * @see https://www.drupal.org/node/1842756
 */
function template_preprocess_item_list(&$variables) {
    $variables['wrapper_attributes'] = new Attribute($variables['wrapper_attributes']);
    foreach ($variables['items'] as &$item) {
        $attributes = [];
        // If the item value is an array, then it is a render array.
        if (is_array($item)) {
            // List items support attributes via the '#wrapper_attributes' property.
            if (isset($item['#wrapper_attributes'])) {
                $attributes = $item['#wrapper_attributes'];
            }
            // Determine whether there are any child elements in the item that are not
            // fully-specified render arrays. If there are any, then the child
            // elements present nested lists and we automatically inherit the render
            // array properties of the current list to them.
            foreach (Element::children($item) as $key) {
                $child =& $item[$key];
                // If this child element does not specify how it can be rendered, then
                // we need to inherit the render properties of the current list.
                if (!isset($child['#type']) && !isset($child['#theme']) && !isset($child['#markup'])) {
                    // Since item-list.html.twig supports both strings and render arrays
                    // as items, the items of the nested list may have been specified as
                    // the child elements of the nested list, instead of #items. For
                    // convenience, we automatically move them into #items.
                    if (!isset($child['#items'])) {
                        // This is the same condition as in
                        // \Drupal\Core\Render\Element::children(), which cannot be used
                        // here, since it triggers an error on string values.
                        foreach ($child as $child_key => $child_value) {
                            if (is_int($child_key) || $child_key === '' || $child_key[0] !== '#') {
                                $child['#items'][$child_key] = $child_value;
                                unset($child[$child_key]);
                            }
                        }
                    }
                    // Lastly, inherit the original theme variables of the current list.
                    $child['#theme'] = $variables['theme_hook_original'];
                    $child['#list_type'] = $variables['list_type'];
                }
            }
        }
        // Set the item's value and attributes for the template.
        $item = [
            'value' => $item,
            'attributes' => new Attribute($attributes),
        ];
    }
}

/**
 * Prepares variables for container templates.
 *
 * Default template: container.html.twig.
 *
 * @param array $variables
 *   An associative array containing:
 *   - element: An associative array containing the properties of the element.
 *     Properties used: #id, #attributes, #children.
 */
function template_preprocess_container(&$variables) {
    $variables['has_parent'] = FALSE;
    $element = $variables['element'];
    // Ensure #attributes is set.
    $element += [
        '#attributes' => [],
    ];
    // Special handling for form elements.
    if (isset($element['#array_parents'])) {
        // Assign an html ID.
        if (!isset($element['#attributes']['id'])) {
            $element['#attributes']['id'] = $element['#id'];
        }
        $variables['has_parent'] = TRUE;
    }
    $variables['children'] = $element['#children'];
    $variables['attributes'] = $element['#attributes'];
}

/**
 * Prepares variables for maintenance task list templates.
 *
 * Default template: maintenance-task-list.html.twig.
 *
 * @param array $variables
 *   An associative array containing:
 *   - items: An associative array of maintenance tasks.
 *     It's the caller's responsibility to ensure this array's items contain no
 *     dangerous HTML such as <script> tags.
 *   - active: The key for the currently active maintenance task.
 */
function template_preprocess_maintenance_task_list(&$variables) {
    $items = $variables['items'];
    $active = $variables['active'];
    $done = isset($items[$active]) || $active == NULL;
    foreach ($items as $k => $item) {
        $variables['tasks'][$k]['item'] = $item;
        $variables['tasks'][$k]['attributes'] = new Attribute();
        if ($active == $k) {
            $variables['tasks'][$k]['attributes']->addClass('is-active');
            $variables['tasks'][$k]['status'] = t('active');
            $done = FALSE;
        }
        else {
            if ($done) {
                $variables['tasks'][$k]['attributes']->addClass('done');
                $variables['tasks'][$k]['status'] = t('done');
            }
        }
    }
}

/**
 * Adds a default set of helper variables for preprocessors and templates.
 *
 * This function is called for every theme hook. It is the first in the
 * sequence of preprocessing functions called when preparing variables for a
 * template.
 *
 * See the @link themeable Default theme implementations topic @endlink for
 * details.
 */
function template_preprocess(&$variables, $hook, $info) {
    // Merge in variables that don't depend on hook and don't change during a
    // single page request.
    // Use the advanced drupal_static() pattern, since this is called very often.
    static $drupal_static_fast;
    if (!isset($drupal_static_fast)) {
        $drupal_static_fast['default_variables'] =& drupal_static(__FUNCTION__);
    }
    $default_variables =& $drupal_static_fast['default_variables'];
    if (!isset($default_variables)) {
        $default_variables = _template_preprocess_default_variables();
    }
    $variables += $default_variables;
    // When theming a render element, merge its #attributes into
    // $variables['attributes'].
    if (isset($info['render element'])) {
        $key = $info['render element'];
        if (isset($variables[$key]['#attributes'])) {
            $variables['attributes'] = AttributeHelper::mergeCollections($variables['attributes'], $variables[$key]['#attributes']);
        }
    }
}

/**
 * Returns hook-independent variables to template_preprocess().
 */
function _template_preprocess_default_variables() {
    // Variables that don't depend on a database connection.
    $variables = [
        'attributes' => [],
        'title_attributes' => [],
        'content_attributes' => [],
        'title_prefix' => [],
        'title_suffix' => [],
        'db_is_active' => !defined('MAINTENANCE_MODE'),
        'is_admin' => FALSE,
        'logged_in' => FALSE,
    ];
    // Give modules a chance to alter the default template variables.
    \Drupal::moduleHandler()->alter('template_preprocess_default_variables', $variables);
    // Tell all templates where they are located.
    $variables['directory'] = \Drupal::theme()->getActiveTheme()
        ->getPath();
    return $variables;
}

/**
 * Prepares variables for HTML document templates.
 *
 * Default template: html.html.twig.
 *
 * @param array $variables
 *   An associative array containing:
 *   - page: A render element representing the page.
 */
function template_preprocess_html(&$variables) {
    $variables['page'] = $variables['html']['page'];
    unset($variables['html']['page']);
    $variables['page_top'] = NULL;
    if (isset($variables['html']['page_top'])) {
        $variables['page_top'] = $variables['html']['page_top'];
        unset($variables['html']['page_top']);
    }
    $variables['page_bottom'] = NULL;
    if (isset($variables['html']['page_bottom'])) {
        $variables['page_bottom'] = $variables['html']['page_bottom'];
        unset($variables['html']['page_bottom']);
    }
    $variables['html_attributes'] = new Attribute();
    // <html> element attributes.
    $language_interface = \Drupal::languageManager()->getCurrentLanguage();
    $variables['html_attributes']['lang'] = $language_interface->getId();
    $variables['html_attributes']['dir'] = $language_interface->getDirection();
    if (isset($variables['db_is_active']) && !$variables['db_is_active']) {
        $variables['db_offline'] = TRUE;
    }
    // Add a variable for the root path. This can be used to create a class and
    // theme the page depending on the current path (e.g. node, admin, user) as
    // well as more specific data like path-frontpage.
    $is_front_page = \Drupal::service('path.matcher')->isFrontPage();
    if ($is_front_page) {
        $variables['root_path'] = FALSE;
    }
    else {
        $system_path = \Drupal::service('path.current')->getPath();
        $variables['root_path'] = explode('/', $system_path)[1];
    }
    $site_config = \Drupal::config('system.site');
    // Construct page title.
    if (isset($variables['page']['#title']) && is_array($variables['page']['#title'])) {
        // Do an early render if the title is a render array.
        $variables['page']['#title'] = (string) \Drupal::service('renderer')->render($variables['page']['#title']);
    }
    if (!empty($variables['page']['#title'])) {
        $head_title = [
            // Marking the title as safe since it has had the tags stripped.
'title' => Markup::create(trim(strip_tags($variables['page']['#title']))),
            'name' => $site_config->get('name'),
        ];
    }
    elseif ($is_front_page) {
        $head_title = [
            'title' => t('Home'),
            'name' => $site_config->get('name'),
        ];
    }
    else {
        $head_title = [
            'name' => $site_config->get('name'),
        ];
        if ($site_config->get('slogan')) {
            $head_title['slogan'] = strip_tags($site_config->get('slogan'));
        }
    }
    $variables['head_title'] = $head_title;
    // @deprecated in Drupal 8.0.0, will be removed before Drupal 9.0.0.
    $variables['head_title_array'] = $head_title;
    // Create placeholder strings for these keys.
    // @see \Drupal\Core\Render\HtmlResponseSubscriber
    $types = [
        'styles' => 'css',
        'scripts' => 'js',
        'scripts_bottom' => 'js-bottom',
        'head' => 'head',
    ];
    $variables['placeholder_token'] = Crypt::randomBytesBase64(55);
    foreach ($types as $type => $placeholder_name) {
        $placeholder = '<' . $placeholder_name . '-placeholder token="' . $variables['placeholder_token'] . '">';
        $variables['#attached']['html_response_attachment_placeholders'][$type] = $placeholder;
    }
}

/**
 * Prepares variables for the page template.
 *
 * Default template: page.html.twig.
 *
 * See the page.html.twig template for the list of variables.
 */
function template_preprocess_page(&$variables) {
    $language_interface = \Drupal::languageManager()->getCurrentLanguage();
    foreach (\Drupal::theme()->getActiveTheme()
        ->getRegions() as $region) {
        if (!isset($variables['page'][$region])) {
            $variables['page'][$region] = [];
        }
    }
    $variables['base_path'] = base_path();
    $variables['front_page'] = Url::fromRoute('<front>')->toString();
    $variables['language'] = $language_interface;
    // An exception might be thrown.
    try {
        $variables['is_front'] = \Drupal::service('path.matcher')->isFrontPage();
    } catch (Exception $e) {
        // If the database is not yet available, set default values for these
        // variables.
        $variables['is_front'] = FALSE;
        $variables['db_is_active'] = FALSE;
    }
    if ($node = \Drupal::routeMatch()->getParameter('node')) {
        $variables['node'] = $node;
    }
}

/**
 * Generate an array of suggestions from path arguments.
 *
 * This is typically called for adding to the suggestions in
 * hook_theme_suggestions_HOOK_alter() or adding to 'attributes' class key
 * variables from within preprocess functions, when wanting to base the
 * additional suggestions or classes on the path of the current page.
 *
 * @param $args
 *   An array of path arguments.
 * @param $base
 *   A string identifying the base 'thing' from which more specific suggestions
 *   are derived. For example, 'page' or 'html'.
 * @param $delimiter
 *   The string used to delimit increasingly specific information. The default
 *   of '__' is appropriate for theme hook suggestions. '-' is appropriate for
 *   extra classes.
 *
 * @return
 *   An array of suggestions, suitable for adding to
 *   hook_theme_suggestions_HOOK_alter() or to $variables['attributes']['class']
 *   if the suggestions represent extra CSS classes.
 */
function theme_get_suggestions($args, $base, $delimiter = '__') {
    // Build a list of suggested theme hooks in order of
    // specificity. One suggestion is made for every element of the current path,
    // though numeric elements are not carried to subsequent suggestions. For
    // example, for $base='page', http://www.example.com/node/1/edit would result
    // in the following suggestions:
    //
    // page__node
    // page__node__%
    // page__node__1
    // page__node__edit
    $suggestions = [];
    $prefix = $base;
    foreach ($args as $arg) {
        // Remove slashes or null per SA-CORE-2009-003 and change - (hyphen) to _
        // (underscore).
        //
        // When we discover templates in @see drupal_find_theme_templates,
        // hyphens (-) are converted to underscores (_) before the theme hook
        // is registered. We do this because the hyphens used for delimiters
        // in hook suggestions cannot be used in the function names of the
        // associated preprocess functions. Any page templates designed to be used
        // on paths that contain a hyphen are also registered with these hyphens
        // converted to underscores so here we must convert any hyphens in path
        // arguments to underscores here before fetching theme hook suggestions
        // to ensure the templates are appropriately recognized.
        $arg = str_replace([
            "/",
            "\\",
            "\x00",
            '-',
        ], [
            '',
            '',
            '',
            '_',
        ], $arg);
        // The percent acts as a wildcard for numeric arguments since
        // asterisks are not valid filename characters on many filesystems.
        if (is_numeric($arg)) {
            $suggestions[] = $prefix . $delimiter . '%';
        }
        $suggestions[] = $prefix . $delimiter . $arg;
        if (!is_numeric($arg)) {
            $prefix .= $delimiter . $arg;
        }
    }
    if (\Drupal::service('path.matcher')->isFrontPage()) {
        // Front templates should be based on root only, not prefixed arguments.
        $suggestions[] = $base . $delimiter . 'front';
    }
    return $suggestions;
}

/**
 * Prepares variables for maintenance page templates.
 *
 * Default template: maintenance-page.html.twig.
 *
 * @param array $variables
 *   An associative array containing:
 *   - content - An array of page content.
 *
 * @see system_page_attachments()
 */
function template_preprocess_maintenance_page(&$variables) {
    // @todo Rename the templates to page--maintenance + page--install.
    template_preprocess_page($variables);
    // @see system_page_attachments()
    $variables['#attached']['library'][] = 'system/maintenance';
    // Maintenance page and install page need branding info in variables because
    // there is no blocks.
    $site_config = \Drupal::config('system.site');
    $variables['logo'] = theme_get_setting('logo.url');
    $variables['site_name'] = $site_config->get('name');
    $variables['site_slogan'] = $site_config->get('slogan');
    // Maintenance page and install page need page title in variable because there
    // are no blocks.
    $variables['title'] = $variables['page']['#title'];
}

/**
 * Prepares variables for install page templates.
 *
 * Default template: install-page.html.twig.
 *
 * @param array $variables
 *   An associative array containing:
 *   - content - An array of page content.
 *
 * @see template_preprocess_maintenance_page()
 */
function template_preprocess_install_page(&$variables) {
    template_preprocess_maintenance_page($variables);
    // Override the site name that is displayed on the page, since Drupal is
    // still in the process of being installed.
    $distribution_name = drupal_install_profile_distribution_name();
    $variables['site_name'] = $distribution_name;
    $variables['site_version'] = drupal_install_profile_distribution_version();
}

/**
 * Prepares variables for region templates.
 *
 * Default template: region.html.twig.
 *
 * Prepares the values passed to the theme_region function to be passed into a
 * pluggable template engine. Uses the region name to generate a template file
 * suggestions.
 *
 * @param array $variables
 *   An associative array containing:
 *   - elements: An associative array containing properties of the region.
 */
function template_preprocess_region(&$variables) {
    // Create the $content variable that templates expect.
    $variables['content'] = $variables['elements']['#children'];
    $variables['region'] = $variables['elements']['#region'];
}

/**
 * Prepares variables for field templates.
 *
 * Default template: field.html.twig.
 *
 * @param array $variables
 *   An associative array containing:
 *   - element: A render element representing the field.
 *   - attributes: A string containing the attributes for the wrapping div.
 *   - title_attributes: A string containing the attributes for the title.
 */
function template_preprocess_field(&$variables, $hook) {
    $element = $variables['element'];
    // Creating variables for the template.
    $variables['entity_type'] = $element['#entity_type'];
    $variables['field_name'] = $element['#field_name'];
    $variables['field_type'] = $element['#field_type'];
    $variables['label_display'] = $element['#label_display'];
    $variables['label_hidden'] = $element['#label_display'] == 'hidden';
    // Always set the field label - allow themes to decide whether to display it.
    // In addition the label should be rendered but hidden to support screen
    // readers.
    $variables['label'] = $element['#title'];
    $variables['multiple'] = $element['#is_multiple'];
    static $default_attributes;
    if (!isset($default_attributes)) {
        $default_attributes = new Attribute();
    }
    // Merge attributes when a single-value field has a hidden label.
    if ($element['#label_display'] == 'hidden' && !$variables['multiple'] && !empty($element['#items'][0]->_attributes)) {
        $variables['attributes'] = AttributeHelper::mergeCollections($variables['attributes'], (array) $element['#items'][0]->_attributes);
    }
    // We want other preprocess functions and the theme implementation to have
    // fast access to the field item render arrays. The item render array keys
    // (deltas) should always be numerically indexed starting from 0, and looping
    // on those keys is faster than calling Element::children() or looping on all
    // keys within $element, since that requires traversal of all element
    // properties.
    $variables['items'] = [];
    $delta = 0;
    while (!empty($element[$delta])) {
        $variables['items'][$delta]['content'] = $element[$delta];
        // Modules (e.g., rdf.module) can add field item attributes (to
        // $item->_attributes) within hook_entity_prepare_view(). Some field
        // formatters move those attributes into some nested formatter-specific
        // element in order have them rendered on the desired HTML element (e.g., on
        // the <a> element of a field item being rendered as a link). Other field
        // formatters leave them within $element['#items'][$delta]['_attributes'] to
        // be rendered on the item wrappers provided by field.html.twig.
        $variables['items'][$delta]['attributes'] = !empty($element['#items'][$delta]->_attributes) ? new Attribute($element['#items'][$delta]->_attributes) : clone $default_attributes;
        $delta++;
    }
}

/**
 * Prepares variables for individual form element templates.
 *
 * Default template: field-multiple-value-form.html.twig.
 *
 * Combines multiple values into a table with drag-n-drop reordering.
 *
 * @param array $variables
 *   An associative array containing:
 *   - element: A render element representing the form element.
 */
function template_preprocess_field_multiple_value_form(&$variables) {
    $element = $variables['element'];
    $variables['multiple'] = $element['#cardinality_multiple'];
    $variables['attributes'] = $element['#attributes'];
    if ($variables['multiple']) {
        $table_id = Html::getUniqueId($element['#field_name'] . '_values');
        $order_class = $element['#field_name'] . '-delta-order';
        $header_attributes = new Attribute([
            'class' => [
                'label',
            ],
        ]);
        if (!empty($element['#required'])) {
            $header_attributes['class'][] = 'js-form-required';
            $header_attributes['class'][] = 'form-required';
        }
        $header = [
            [
                'data' => [
                    '#prefix' => '<h4' . $header_attributes . '>',
                    '#markup' => $element['#title'],
                    '#suffix' => '</h4>',
                ],
                'colspan' => 2,
                'class' => [
                    'field-label',
                ],
            ],
            t('Order', [], [
                'context' => 'Sort order',
            ]),
        ];
        $rows = [];
        // Sort items according to '_weight' (needed when the form comes back after
        // preview or failed validation).
        $items = [];
        $variables['button'] = [];
        foreach (Element::children($element) as $key) {
            if ($key === 'add_more') {
                $variables['button'] =& $element[$key];
            }
            else {
                $items[] =& $element[$key];
            }
        }
        usort($items, '_field_multiple_value_form_sort_helper');
        // Add the items as table rows.
        foreach ($items as $item) {
            $item['_weight']['#attributes']['class'] = [
                $order_class,
            ];
            // Remove weight form element from item render array so it can be rendered
            // in a separate table column.
            $delta_element = $item['_weight'];
            unset($item['_weight']);
            $cells = [
                [
                    'data' => '',
                    'class' => [
                        'field-multiple-drag',
                    ],
                ],
                [
                    'data' => $item,
                ],
                [
                    'data' => $delta_element,
                    'class' => [
                        'delta-order',
                    ],
                ],
            ];
            $rows[] = [
                'data' => $cells,
                'class' => [
                    'draggable',
                ],
            ];
        }
        $variables['table'] = [
            '#type' => 'table',
            '#header' => $header,
            '#rows' => $rows,
            '#attributes' => [
                'id' => $table_id,
                'class' => [
                    'field-multiple-table',
                ],
            ],
            '#tabledrag' => [
                [
                    'action' => 'order',
                    'relationship' => 'sibling',
                    'group' => $order_class,
                ],
            ],
        ];
        if (!empty($element['#description'])) {
            $description_id = $element['#attributes']['aria-describedby'];
            $description_attributes['id'] = $description_id;
            $variables['description']['attributes'] = new Attribute($description_attributes);
            $variables['description']['content'] = $element['#description'];
            // Add the description's id to the table aria attributes.
            $variables['table']['#attributes']['aria-describedby'] = $element['#attributes']['aria-describedby'];
        }
    }
    else {
        $variables['elements'] = [];
        foreach (Element::children($element) as $key) {
            $variables['elements'][] = $element[$key];
        }
    }
}

/**
 * Prepares variables for breadcrumb templates.
 *
 * Default template: breadcrumb.html.twig.
 *
 * @param array $variables
 *   An associative array containing:
 *   - links: A list of \Drupal\Core\Link objects which should be rendered.
 */
function template_preprocess_breadcrumb(&$variables) {
    $variables['breadcrumb'] = [];
    
    /** @var \Drupal\Core\Link $link */
    foreach ($variables['links'] as $key => $link) {
        $variables['breadcrumb'][$key] = [
            'text' => $link->getText(),
            'url' => $link->getUrl()
                ->toString(),
        ];
    }
}

/**
 * Callback for usort() within template_preprocess_field_multiple_value_form().
 *
 * Sorts using ['_weight']['#value']
 */
function _field_multiple_value_form_sort_helper($a, $b) {
    $a_weight = is_array($a) && isset($a['_weight']['#value']) ? $a['_weight']['#value'] : 0;
    $b_weight = is_array($b) && isset($b['_weight']['#value']) ? $b['_weight']['#value'] : 0;
    return $a_weight - $b_weight;
}

/**
 * Provides theme registration for themes across .inc files.
 */
function drupal_common_theme() {
    return [
        // From theme.inc.
'html' => [
            'render element' => 'html',
        ],
        'page' => [
            'render element' => 'page',
        ],
        'page_title' => [
            'variables' => [
                'title' => NULL,
            ],
        ],
        'region' => [
            'render element' => 'elements',
        ],
        'time' => [
            'variables' => [
                'timestamp' => NULL,
                'text' => NULL,
                'attributes' => [],
            ],
        ],
        'datetime_form' => [
            'render element' => 'element',
        ],
        'datetime_wrapper' => [
            'render element' => 'element',
        ],
        'status_messages' => [
            'variables' => [
                'status_headings' => [],
                'message_list' => NULL,
            ],
        ],
        'links' => [
            'variables' => [
                'links' => [],
                'attributes' => [
                    'class' => [
                        'links',
                    ],
                ],
                'heading' => [],
                'set_active_class' => FALSE,
            ],
        ],
        'dropbutton_wrapper' => [
            'variables' => [
                'children' => NULL,
            ],
        ],
        'image' => [
            // HTML 4 and XHTML 1.0 always require an alt attribute. The HTML 5 draft
            // allows the alt attribute to be omitted in some cases. Therefore,
            // default the alt attribute to an empty string, but allow code providing
            // variables to image.html.twig templates to pass explicit NULL for it to
            // be omitted. Usually, neither omission nor an empty string satisfies
            // accessibility requirements, so it is strongly encouraged for code
            // building variables for image.html.twig templates to pass a meaningful
            // value for the alt variable.
            // - http://www.w3.org/TR/REC-html40/struct/objects.html#h-13.8
            // - http://www.w3.org/TR/xhtml1/dtds.html
            // - http://dev.w3.org/html5/spec/Overview.html#alt
            // The title attribute is optional in all cases, so it is omitted by
            // default.
'variables' => [
                'uri' => NULL,
                'width' => NULL,
                'height' => NULL,
                'alt' => '',
                'title' => NULL,
                'attributes' => [],
                'sizes' => NULL,
                'srcset' => [],
                'style_name' => NULL,
            ],
        ],
        'breadcrumb' => [
            'variables' => [
                'links' => [],
            ],
        ],
        'table' => [
            'variables' => [
                'header' => NULL,
                'rows' => NULL,
                'footer' => NULL,
                'attributes' => [],
                'caption' => NULL,
                'colgroups' => [],
                'sticky' => FALSE,
                'responsive' => TRUE,
                'empty' => '',
            ],
        ],
        'tablesort_indicator' => [
            'variables' => [
                'style' => NULL,
            ],
        ],
        'mark' => [
            'variables' => [
                'status' => MARK_NEW,
            ],
        ],
        'item_list' => [
            'variables' => [
                'items' => [],
                'title' => '',
                'list_type' => 'ul',
                'wrapper_attributes' => [],
                'attributes' => [],
                'empty' => NULL,
                'context' => [],
            ],
        ],
        'feed_icon' => [
            'variables' => [
                'url' => NULL,
                'title' => NULL,
            ],
        ],
        'progress_bar' => [
            'variables' => [
                'label' => NULL,
                'percent' => NULL,
                'message' => NULL,
            ],
        ],
        'indentation' => [
            'variables' => [
                'size' => 1,
            ],
        ],
        // From theme.maintenance.inc.
'maintenance_page' => [
            'render element' => 'page',
        ],
        'install_page' => [
            'render element' => 'page',
        ],
        'maintenance_task_list' => [
            'variables' => [
                'items' => NULL,
                'active' => NULL,
                'variant' => NULL,
            ],
        ],
        'authorize_report' => [
            'variables' => [
                'messages' => [],
                'attributes' => [],
            ],
            'includes' => [
                'core/includes/theme.maintenance.inc',
            ],
            'template' => 'authorize-report',
        ],
        // From pager.inc.
'pager' => [
            'render element' => 'pager',
        ],
        // From menu.inc.
'menu' => [
            'variables' => [
                'menu_name' => NULL,
                'items' => [],
                'attributes' => [],
            ],
        ],
        'menu_local_task' => [
            'render element' => 'element',
        ],
        'menu_local_action' => [
            'render element' => 'element',
        ],
        'menu_local_tasks' => [
            'variables' => [
                'primary' => [],
                'secondary' => [],
            ],
        ],
        // From form.inc.
'input' => [
            'render element' => 'element',
        ],
        'select' => [
            'render element' => 'element',
        ],
        'fieldset' => [
            'render element' => 'element',
        ],
        'details' => [
            'render element' => 'element',
        ],
        'radios' => [
            'render element' => 'element',
        ],
        'checkboxes' => [
            'render element' => 'element',
        ],
        'form' => [
            'render element' => 'element',
        ],
        'textarea' => [
            'render element' => 'element',
        ],
        'form_element' => [
            'render element' => 'element',
        ],
        'form_element_label' => [
            'render element' => 'element',
        ],
        'vertical_tabs' => [
            'render element' => 'element',
        ],
        'container' => [
            'render element' => 'element',
        ],
        // From field system.
'field' => [
            'render element' => 'element',
        ],
        'field_multiple_value_form' => [
            'render element' => 'element',
        ],
    ];
}