dpl_theme.theme

<?php
/**
 * @file
 * Functions to support theming in the BD Client SASS Starterkit subtheme.
 */

use Drupal\Core\Form\FormStateInterface;

/**
  * Implements hook_theme_suggestions_HOOK_alter for blocks.
  */
function dpl_theme_theme_suggestions_block_alter(&$suggestions, $variables) {

   // Load theme suggestions for blocks from parent theme.
  foreach ($suggestions as &$suggestion) {
    $suggestion = str_replace('dpl_theme_', 'islandora_base_theme_', $suggestion);
  }
}

function dpl_theme_form_system_theme_settings_alter(&$form, FormStateInterface $form_state) {
  $form['components']['navbar']['bootstrap_barrio_navbar_top_background']['#options'] = [
    'bg-primary' => t('Primary'),
    'bg-secondary' => t('Secondary'),
    'bg-light' => t('Light'),
    'bg-dark' => t('Dark'),
    'bg-white' => t('White'),
    'bg-transparent' => t('Transparent'),
  ];
  $form['components']['navbar']['bootstrap_barrio_navbar_background']['#options'] = [
    'bg-primary' => t('Primary'),
    'bg-secondary' => t('Secondary'),
    'bg-light' => t('Light'),
    'bg-dark' => t('Dark'),
    'bg-white' => t('White'),
    'bg-transparent' => t('Transparent'),
  ];
  $form['fonts']['fonts']['bootstrap_barrio_google_fonts']['#options']['opensans'] = 'Open Sans';
}

function dpl_theme_preprocess_page(&$variables) {
  $fonts = theme_get_setting('bootstrap_barrio_google_fonts');
  if ($fonts)
    $variables['#attached']['library'][] = (in_array($fonts, ['opensans']) ? 'dpl_theme' : 'bootstrap_barrio' ) . '/' . $fonts;
}

/**
 * Implements hook_preprocess_block().
 */
function dpl_theme_preprocess_block(&$variables) {
  // set is front page variable
  $variables['is_front'] = \Drupal::service('path.matcher')->isFrontPage();
}

/**
 * Implements hook_preprocess_view_view().
 */
function dpl_theme_preprocess_views_view(&$variables) {
  $variable['additional_classes'] = ['view-grid'];
}