edlp_d8/core/profiles/demo_umami/themes/umami/umami.theme

<?php

/**
 * @file
 * Functions to support theming in the Umami theme.
 */

use Drupal\Component\Utility\Html;
use Drupal\Core\Form\FormStateInterface;
use Symfony\Cmf\Component\Routing\RouteObjectInterface;

/**
 * Implements hook_preprocess_HOOK() for HTML document templates.
 *
 * Adds body classes if certain regions have content.
 */
function umami_preprocess_html(&$variables) {
  // Add a sidebar class if the sidebar has content in it.
  if (!empty($variables['page']['sidebar'])) {
    $variables['attributes']['class'][] = 'two-columns';
    $variables['#attached']['library'][] = 'umami/two-columns';
  }
  else {
    $variables['attributes']['class'][] = 'one-column';
  }
}

/**
 * Implements hook_preprocess_field().
 */
function umami_preprocess_field(&$variables, $hook) {
  $element = $variables['element'];
  // Add class to label and items fields to be styled using the meta styles.
  if (isset($element['#field_name'])) {
    if (
      $element['#field_name'] == 'field_recipe_category' ||
      $element['#field_name'] == 'field_tags' ||
      $element['#field_name'] == 'field_difficulty') {
      $variables['attributes']['class'] = 'label-items';
    }
  }
}

/**
 * Implements hook_preprocess_block().
 */
function umami_preprocess_block(&$variables) {
  $variables['title_attributes']['class'][] = 'block__title';
  // Add a class indicating the custom block bundle.
  if (isset($variables['elements']['content']['#block_content'])) {
    $variables['attributes']['class'][] = Html::getClass('block-type-' . $variables['elements']['content']['#block_content']->bundle());
  }
}

/**
 * Implements hook_theme_suggestions_HOOK_alter() for form templates.
 */
function umami_theme_suggestions_block_alter(array &$suggestions, array $variables) {
  // Block suggestions for custom block bundles.
  if (isset($variables['elements']['content']['#block_content'])) {
    array_splice($suggestions, 1, 0, 'block__bundle__' . $variables['elements']['content']['#block_content']->bundle());
  }
}

/**
 * Implements hook_preprocess_breadcrumb().
 */
function umami_preprocess_breadcrumb(&$variables) {
  // We are creating a variable for the Current Page Title, to allow us to print
  // it after the breadcrumbs loop has run.
  $request = \Drupal::request();
  if ($route = $request->attributes->get(RouteObjectInterface::ROUTE_OBJECT)) {
    // Search page titles aren't resolved using the title_resolver service - it
    // will always return 'Search' instead of 'Search for [term]', which would
    // give us a breadcrumb of Home >> Search >> Search.
    // @see https://www.drupal.org/project/drupal/issues/2359901
    // @see https://www.drupal.org/project/drupal/issues/2403359
    if (($entity = $request->attributes->get('entity')) && $entity->getEntityTypeId() === 'search_page') {
      $variables['current_page_title'] = $entity->getPlugin()->suggestedTitle();
    }
    else {
      $variables['current_page_title'] = \Drupal::service('title_resolver')->getTitle($request, $route);
    }
  }
  // Since we are printing the 'Current Page Title', add the URL cache context.
  // If we don't, then we might end up with something like
  // "Home > Articles" on the Recipes page, which should read "Home > Recipes".
  $variables['#cache']['contexts'][] = 'url';
}

/**
 * Implements hook_form_FORM_ID_alter().
 */
function umami_form_search_block_form_alter(&$form, FormStateInterface $form_state) {
  $form['keys']['#attributes']['placeholder'] = t('Search by keyword, ingredient, dish');
}