<?php
function smarty_block_MTIfIsAncestor($args, $content, &$ctx, &$repeat) {
    $localvars = array('conditional', 'else_content');
    if (!isset($content)) {
       require_once("MTUtil.php");
       $cat = get_category_context($ctx);
       $ctx->localize($localvars);
       list($child) = $ctx->mt->db->fetch_categories(array('label' => $args['child'], 'blog_id' => $ctx->stash('blog_id'), 'show_empty' => 1));
       if ($child) {
           if (!_is_ancestor($cat, $child, $ctx))
               $child = null;
       }
       $ctx->stash('else_content', null);
       $ctx->stash('conditional', $child ? 1 : 0);
    } else {
       if (!$ctx->stash('conditional'))
           $content = $ctx->stash('else_content');
       $ctx->restore($localvars);
    }
    return $content;
}

function _is_ancestor(&$cat, &$possible_child, &$ctx) {
    # Catch the different blog edge case
    if ($cat['category_blog_id'] != $possible_child['category_blog_id']) 
        return 0;

    if ($cat['category_id'] == $possible_child['category_id']) 
        return 1;

    # Keep having the child bump up one level in the hierarchy
    # to see if it ever reaches the current category
    # (more efficient than descending from the current category
    # as the children lists do not need to be calculated)
    while ($id = $possible_child['category_parent']) {
        $possible_child = $ctx->mt->db->fetch_category($id);
        if ($cat['category_id'] == $id)
            return 1;
    }

    # Looks like we didn't find it
    return 0;
}
?>