How can I include a dropdown in menu_local_tasks tabs?

Question

I am trying to include a Bootstrap style dropdown in the local_tasks tabs on a section of my website. I thought I might be able to accomplish this with the 'theme callback' option of 'HOOK_MENU', but it doesn't run the custom callback. Any ideas on a good way to accomplish this?

Menu:

    $items['module/submenu/tab'] = array(
    'title' => 'Title',
    'page callback' => 'mymodule_menu_callback',
    'access arguments' => array('access content'),
    'theme callback' => 'mymodule_menu_local_task_dropdown',
    'type' => MENU_LOCAL_TASK,
);

Callback:

function mymodule_menu_local_task_dropdown($variables) {
 $link = $variables['element']['#link'];
 $link_text = $link['title'];
 $classes = array();

 if (!empty($variables['element']['#active'])) {
 // Add text to indicate active tab for non-visual users.
 $active = '<span class="element-invisible">' . t('(active tab)') . '</span>';

 // If the link does not contain HTML already, check_plain() it now.
 // After we set 'html'=TRUE the link will not be sanitized by l().
 if (empty($link['localized_options']['html'])) {
  $link['title'] = check_plain($link['title']);
 }
 $link['localized_options']['html'] = TRUE;
 $link_text = t('!local-task-title!active', array('!local-task-title' => $link['title'], '!active' => $active));

 $classes[] = 'active';
}

$classes[] = 'dropdown';

//haven't written this part yet
$dropdown = 'build dropdown';

return '<li class="' . implode(' ', $classes) . '">' . l($link_text, $link['href'], $link['localized_options']) . $dropdown . "</li>\n";
}

What I'm looking for:

Answer 1

For the drop-down menu you need include drop-down JavaScript in the "page callback". See drupal_add_library() function.

And I recommend for you pay attention to "CTools module".

"Drop-Down Menu" Code from CTools module:

  // Show examples of ctools javascript widgets
  $output .= '<h2>' . t('CTools Javascript Widgets') . '</h2>';

  // Create a drop down menu
  $links = array();
  $links[] = array(
    'title' => t('Link 1'),
    'href' => $_GET['q'],
  );
  $links[] = array(
    'title' => t('Link 2'),
    'href' => $_GET['q'],
  );
  $links[] = array(
    'title' => t('Link 3'),
    'href' => $_GET['q'],
  );

  $output .= '<h3>' . t('Drop Down Menu') . '</h3>';
  $output .= theme('ctools_dropdown', array('title' => t('Click to Drop Down'), 'links' => $links));

Answer 2

I have figured out a way to do it for now, but doesn't seem like a great solution and adds two calls to every tab rendered. Since I wasn't able to get the custom callback to work, I overrode theme_menu_local_task with some ideas from https://stackoverflow.com/questions/2716787/how-to-get-all-the-menu-items-below-a-certain-parent-in-drupal. Basically I test the path for children and output the dropdown if they exist.

    function mymodule_menu_local_task($variables) {

    $link = $variables['element']['#link'];
    $link_text = $link['title'];
    $classes = array();

    if (!empty($variables['element']['#active'])) {
        // Add text to indicate active tab for non-visual users.
        $active = '<span class="element-invisible">' . t('(active tab)') . '</span>';

        // If the link does not contain HTML already, check_plain() it now.
        // After we set 'html'=TRUE the link will not be sanitized by l().
        if (empty($link['localized_options']['html'])) {
            $link['title'] = check_plain($link['title']);
        }
        $link['localized_options']['html'] = TRUE;
        $link_text = t('!local-task-title!active', array('!local-task-title' => $link['title'], '!active' => $active));

        $classes[] = 'active';
    }

    //check to see if menu item has children
    $parent = menu_link_get_preferred($variables['element']['#link']['path']);
    $parameters = array(
        'active_trail' => array($parent['plid']),
        'only_active_trail' => FALSE,
        'min_depth' => $parent['depth']+1,
        'max_depth' => $parent['depth']+1,
        'conditions' => array('plid' => $parent['mlid']),
    );
    $children = menu_build_tree($parent['menu_name'], $parameters);

    //if item has children, output as a dropdown
    if (!empty($children)) {
        $classes[] = 'download';
        $link['localized_options']['html'] = TRUE;
        $link['localized_options']['attributes']['data-toggle'] = 'dropdown';
        $link['localized_options']['attributes']['class'] = 'dropdown-toggle';
        $dropdown = '';
        foreach ($children as $item) {
            $dropdown .= '<li>'. l($item['link']['link_title'], $item['link']['link_path']) .'</li>';
        }
        $dropdown = '<ul class="dropdown-menu" role="menu">'. $dropdown .'</ul>';
        return '<li class="' . implode(' ', $classes) . '">' . l($link_text.'<span class="caret"></span>', $link['href'], $link['localized_options']) . $dropdown . "</li>\n";
    } else {
        return '<li class="' . implode(' ', $classes) . '">' . l($link_text, $link['href'], $link['localized_options']) . "</li>\n";
    } 
}