LlamaContextual.php

<?php

/**
 * @file
 * Contains \Drupal\ckeditor_test\Plugin\CKEditorPlugin\LlamaContextual.
 */
namespace Drupal\ckeditor_test\Plugin\CKEditorPlugin;

use Drupal\ckeditor\CKEditorPluginContextualInterface;
use Drupal\Component\Plugin\PluginBase;
use Drupal\ckeditor\Annotation\CKEditorPlugin;
use Drupal\Core\Annotation\Translation;
use Drupal\editor\Plugin\Core\Entity\Editor;

/**
 * Defines a "Llama" plugin, with a contextually enabled "llama" feature.
 *
 * @CKEditorPlugin(
 *   id = "llama_contextual",
 *   label = @Translation("Contextual Llama")
 * )
 */
class LlamaContextual extends Llama implements CKEditorPluginContextualInterface {

  /**
   * Implements \Drupal\ckeditor\Plugin\CKEditorPluginContextualInterface::isEnabled().
   */
  function isEnabled(Editor $editor) {

    // Automatically enable this plugin if the Underline button is enabled.
    foreach ($editor->settings['toolbar']['buttons'] as $row) {
      if (in_array('Strike', $row)) {
        return TRUE;
      }
    }
    return FALSE;
  }

  /**
   * Implements \Drupal\ckeditor\Plugin\CKEditorPluginInterface::getFile().
   */
  function getFile() {
    return drupal_get_path('module', 'ckeditor_test') . '/js/llama_contextual.js';
  }

}