Programmatically load a panels pane

/**
 * Renders a single pane from the "test_panels_page" Ctools Page.
 *
 * @param integer $pane_id The numeric pane ID for each pane in a panels variant ctools page. (This id is in the panels_pane table.)
 * @param integer $uid The User ID we require for the Context.
 * @return string The rendered markup of the pane.
 */
function render_pane_render($pane_id, $uid) {
  // Do some bootstrapping so we can use some Panels files.
  module_load_include('inc', 'panels', 'plugins/task_handlers/panel_context');
  module_load_include('inc', 'panels', 'includes/plugins');
 
  // Load up an existing Ctools Page called "test_panels_page"
  $ctools_page = page_manager_get_page_cache('page-test_panels_page');
 
  // Turn the result array into just the object at the first index of the array.
  $handler = reset($ctools_page->handlers);
 
  // Load the display object.
  $display = panels_panel_context_get_display($handler);
 
  // Load the user object that our Page Context requires.
  $account = user_load($uid);
 
  // Create a basic context for the user account argument.
  $context = new ctools_context(array(
    'entity:user',
    'entity',
    'user',
  ), $account);
  // Stub out some
  $context->argument = $uid;
  $context->title = $account->name;
  $context->empty = FALSE;
  $context->id = 'argument_entity_id:user_1';
  $context->original_argument = $uid;
  $context->plugin = "user";
 
  $display->args[] = $account->uid;
  $display->context[$context->id] = $context;
 
  // Get the display's renderer object.
  $renderer = panels_get_renderer($handler->conf['pipeline'], $display);
 
  $renderer->prepare();
  // Render an individual pane of the potential multiple panes on the ctools page.
  $content = $renderer->render_pane($renderer->prepared['panes'][$pane_id]);
 
  // Return the rendered markup to the calling process.
  return $content;
}
 
// The below is optional but nice if we want easy access to a pane's ID for AJAX.
/**
 * Implments hook_preprocess_HOOK_ID().
 */
function render_pane_preprocess_panels_pane(&$variables) {
  // Add the a pane's DB ID to each wrapper so we can grab it for potential AJAX pane rendering.
  $variables['classes_array'][] = 'pane-id';
  $variables['classes_array'][] = 'pane-id-' . $variables['pane']->pid;
  $variables['attributes_array']['data-pane-id'] = $variables['pane']->pid;
}