adaptivetheme-8.x-3.x-dev/at_core/forms/ext/devel.php

<?php

/**
 * @file
 * Generate form elements for the Devel settings.
 */

use Drupal\Component\Utility\Html;

// Development settings.
$form['devel'] = [
  '#type' => 'details',
  '#title' => t('Developer tools'),
  '#group' => 'extension_settings',
  '#description' => t('Tools to aid theme development.'),
];

// Show page suggestions.
$form['devel']['settings_show_page_suggestions'] = [
  '#type' => 'checkbox',
  '#title' => t('Show Page Suggestions'),
  '#description' => t('Show all template suggestions for the current page. Appears in the messages area.'),
  '#default_value' => theme_get_setting('settings.show_page_suggestions', $theme),
];

// Window size.
$form['devel']['settings_show_window_size'] = [
  '#type' => 'checkbox',
  '#title' => t('Show Window Size'),
  '#description' => t('Shows the window width (in pixels and ems) in the bottom right corner of the screen. Works for any device or browser that supports JavaScript.'),
  '#default_value' => theme_get_setting('settings.show_window_size', $theme),
];

// Enable LiveReload.
$form['devel']['live_reload'] = [
  '#type' => 'fieldset',
  '#title' => t('Live Reload'),
];

$form['devel']['live_reload']['settings_enable_live_reload'] = [
  '#type' => 'checkbox',
  '#title' => t('LiveReload'),
  '#description' => t('Add the LiveReload script the page (this will trigger your LiveReload browser extension to connect).'),
  '#default_value' => theme_get_setting('settings.enable_live_reload', $theme),
];

$form['devel']['live_reload']['settings_live_reload_port'] = [
  '#type' => 'textfield',
  '#size' => 5,
  '#maxlength' => 5,
  '#title' => t('LiveReload Port'),
  '#description' => t('Change the port number, this should match the port in your watch tasks in Gruntfile.js. By default this is set to 1337'),
  '#default_value' => Html::escape(theme_get_setting('settings.live_reload_port', $theme)),
  '#states' => [
    'visible' => ['input[name="settings_enable_live_reload"]' => ['checked' => TRUE]],
  ],
];

// Neutralize Toolbar.
$form['devel']['settings_nuke_toolbar'] = [
  '#type' => 'checkbox',
  '#title' => t('Neutralize Toolbar'),
  '#default_value' => theme_get_setting('settings.nuke_toolbar', $theme),
  '#description' => t('Completely removes the toolbar in the front end by hiding it with CSS and overriding all it\'s CSS rules.'),
];