/Drupal 8

function hook_form_system_theme_settings_alter

hook_form_system_theme_settings_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state)

Allow themes to alter the theme-specific settings form.

With this hook, themes can alter the theme-specific settings form in any way allowable by Drupal's Form API, such as adding form elements, changing default values and removing form elements. See the Form API documentation on api.drupal.org for detailed information.

Note that the base theme's form alterations will be run before any sub-theme alterations.


$form: Nested array of form elements that comprise the form.

$form_state: The current state of the form.

Related topics

Define functions that alter the behavior of Drupal core.


core/lib/Drupal/Core/Render/theme.api.php, line 530
Hooks and documentation related to the theme and render system.


function hook_form_system_theme_settings_alter(&$form, \Drupal\Core\Form\FormStateInterface $form_state) {
  // Add a checkbox to toggle the breadcrumb trail.
  $form['toggle_breadcrumb'] = array(
    '#type' => 'checkbox',
    '#title' => t('Display the breadcrumb'),
    '#default_value' => theme_get_setting('features.breadcrumb'),
    '#description' => t('Show a trail of links from the homepage to the current page.'),

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