Bueno, yo no he buscado demasiado, pero he encontrado dos archivos en los que se le da valor a $context.
El primero es index.php, en la raiz del foro. Ahí se crea la array:
Código PHP:
$context = array();
El otro es Display.php, en Raíz del foro > Sources.
Se definen algunos valores de la array.
Código PHP:
// Information about the current topic...
$context['is_locked'] = $topicinfo['locked'];
$context['is_sticky'] = $topicinfo['is_sticky'];
$context['is_very_hot'] = $topicinfo['num_replies'] >= $modSettings['hotTopicVeryPosts'];
$context['is_hot'] = $topicinfo['num_replies'] >= $modSettings['hotTopicPosts'];
$context['is_approved'] = $topicinfo['approved'];
// We don't want to show the poll icon in the topic class here, so pretend it's not one.
$context['is_poll'] = false;
determineTopicClass($context);
$context['is_poll'] = $topicinfo['id_poll'] > 0 && $modSettings['pollMode'] == '1' && allowedTo('poll_view');
// Did this user start the topic or not?
$context['user']['started'] = $user_info['id'] == $topicinfo['id_member_started'] && !$user_info['is_guest'];
$context['topic_starter_id'] = $topicinfo['id_member_started'];
// Set the topic's information for the template.
$context['subject'] = $topicinfo['subject'];
$context['num_views'] = $topicinfo['num_views'];
$context['mark_unread_time'] = $topicinfo['new_from'];
Seguro que hay más archivos en los que se le dan valores.
Edito: Si os interesa saber todo lo que contiene $context, basta con user la función print_r:
Código PHP:
echo '<pre>'; print_r($context); echo '</pre>';
Así aparecerán todos los valores de la array.