wxt-8.x-3.011/modules/custom/wxt_ext/wxt_ext_blocks/wxt_ext_blocks.module

<?php

/**
 * @file
 * Contains wxt_ext_blocks.module.
 */

use Drupal\Core\Form\FormStateInterface;
use Drupal\block\Entity\Block;

/**
 * Implements hook_form_FORM_ID_alter().
 */
function wxt_ext_blocks_form_block_form_alter(&$form, FormStateInterface $form_state, $form_id) {
  /** @var \Drupal\block\BlockInterface $block */
  $block = $form_state->getFormObject()->getEntity();

  // This will automatically be saved in the third party settings.
  $form['third_party_settings']['#tree'] = TRUE;
  $form['third_party_settings']['wxt_ext_blocks']['display_title_invisible'] = [
    '#type' => 'checkbox',
    '#title' => t('Display invisible title'),
    '#default_value' => $block->getThirdPartySetting('wxt_ext_blocks', 'display_title_invisible'),
    '#states' => [
      'visible' => [
        ':input[name="settings[label_display]"]' => ['checked' => TRUE],
      ],
    ],
  ];
}

/**
 * Implements hook_preprocess_HOOK().
 */
function wxt_ext_blocks_preprocess_block(&$variables) {
  // Blocks coming from page manager widget does not have id.
  if (!empty($variables['elements']['#id'])) {
    $block = Block::load($variables['elements']['#id']);
    if ($block) {
      $label_display = $block->get('settings')['label_display'] == 'visible' ? TRUE : FALSE;
      $variables['label_display'] = $label_display;
      $display_title_invisible = $block->getThirdPartySetting('wxt_ext_blocks', 'display_title_invisible');
      if ($label_display && $display_title_invisible) {
        $variables['display_title_invisible'] = TRUE;
      }
    }
  }
}