How do I programmatically check if a context is active?

Question

How do I see which contexts are active on the page?

I can't find any ContextManager object in hook_preprocess_page().

Answer 1

I figured it out: The Context module defines a service for getting the ContextManager object, which has getActiveContexts(). You can obtain it using the following code.

$activeContexts = \Drupal::service('context.manager')->getActiveContexts();

I need to read Service Container.

Answer 2

You can use this snippet in template_preprocess_page():

  // Pass vars to page.html.twig depending on active contexts
  $active_contexts = \Drupal::service('context.manager')->getActiveContexts();

  $vars['is_my_context_active'] = FALSE;
  foreach ($active_contexts as $context) {
    if ($context->getName() == 'my_context') {
      $vars['is_my_context_active'] = TRUE;
      break;
    }
  }