Issue #3268007 by RenatoG: Create the Settings to include the maxlength to be configurable

block_class.settings:

  path: '/admin/config/content/block-class/settings'

  defaults:

    _title: 'Block Class Settings'

    _form: 'Drupal\block_class\Form\BlockClassSettingsForm'

  requirements:

    _permission: 'administer block classes'

 No newline at end of file

<?php

namespace Drupal\block_class\Form;

use Drupal\Core\Form\ConfigFormBase;

use Drupal\Core\Form\FormStateInterface;

/**

 * Form for Block Class Settings.

 */

class BlockClassSettingsForm extends ConfigFormBase {

  /**

   * {@inheritdoc}

   */

  public function getFormId() {

    return 'block_class_admin_settings';

  }

  /**

   * {@inheritdoc}

   */

  protected function getEditableConfigNames() {

    return [

      'block_class.settings',

    ];

  }

  /**

   * {@inheritdoc}

   */

  public function buildForm(array $form, FormStateInterface $form_state) {

    $config = $this->config('block_class.settings');

    $form['global_settings'] = [

      '#type' => 'details',

      '#title' => $this->t('Global Settings'),

      '#open' => TRUE,

    ];

    $maxlength_block_class_field = 255;

    if (!empty($config->get('maxlength_block_class_field'))) {

      $maxlength_block_class_field = $config->get('maxlength_block_class_field');

    }

    $form['global_settings']['maxlength_block_class_field'] = [

      '#title' => $this->t("Maxlength on block class field"),

      '#type' => 'number',

      '#description' => $this->t('This will be the default maxlength value for the "maxlength" field. The default is 255.'),

      '#default_value' => $maxlength_block_class_field,

    ];

    $form['actions'] = [

      '#type' => 'actions',

    ];

    $form['actions']['submit'] = [

      '#type' => 'submit',

      '#value' => $this->t('Submit'),

    ];

    return $form;

  }

}