Support default layouts and content for layout paragraphs

Hi all,

I have a patch for the newer versions of layout paragraphs as we required a solution, works with the 1.0 hook as we were using before. It was something I put together to get it working. Hoping it might breathe some new life into this thread!

I wonder whether we should be dispatching events rather than alter hooks. Event subscribers are more flexible than alter hooks if you need to run before or after another module's implementation, more self-documenting, and more IDE-friendly.

Hi, tried patch at #31. Patch applied no problem but I still can't set a default layout paragraph. When I try to set one I get the error:

Warning: array_flip(): Can only flip string and integer values, entry skipped in Drupal\Core\Entity\ContentEntityStorageBase->loadMultipleRevisions() (line 667 of core/lib/Drupal/Core/Entity/ContentEntityStorageBase.php).

Any ideas?

Adding some findings to the topic.

I just wanted to select a default layout for a "section" of my site.
I don't really want to set default content. Just select a the specific layout.

Got there with:

/**
 * Implements hook_form_FORM_ID_alter().
 */
function MY_MODULE_form_layout_paragraphs_component_form_alter(array &$form, FormStateInterface &$form_state) {
  if (isset($form['layout_paragraphs'])) {
    array_unshift(
      $form['layout_paragraphs']['#process'],
      [MyModificationClass::class, 'setDefaultLayout']
    );
  }
}

declare(strict_types=1);

namespace Drupal\MY_MODULE\Form;

use Drupal\Core\Form\FormStateInterface;

/**
 * Set the default selected layout for the layout paragraphs component form.
 */
final class MyModificationClass {

  /**
   * Form #process callback.
   */
  public static function setDefaultLayout(array $element, FormStateInterface $form_state, array &$form): array {
    /** @var \Drupal\paragraphs\ParagraphInterface $paragraph */
    $paragraph = $form['#paragraph'];
    if ($paragraph->bundle() === 'section') {
      $behavior_settings = $paragraph->getAllBehaviorSettings()['layout_paragraphs'] ?? [];

      if (empty($behavior_settings['layout'])) {
        $behavior_settings['layout'] = 'one_column_narrow';
        $paragraph->setBehaviorSettings('layout_paragraphs', $behavior_settings);
      }
    }

    return $element;
  }
}

Change out MY_MODULE, section, one_column_narrow to fit your needs - yey, default layout set.