Index: nice_menus.module
===================================================================
--- nice_menus.module	(revision 1032)
+++ nice_menus.module	(working copy)
@@ -237,6 +237,27 @@
     drupal_add_css(drupal_get_path('module', 'nice_menus') .'/nice_menus_default.css');
   }
 }
+
+/**
+ * Builds the active trail from the page's menu data.
+ *
+ * @param $page_menu
+ *   The menu data for a page.
+ * @return
+ *   An array of parent menu item ids.
+ */
+function nice_menus_build_page_trail($page_menu) {
+  $trail = array();
+ foreach ($page_menu as $item) {
+    if ($item['link']['in_active_trail']) {
+      $trail[] = $item['link']['mlid'];
+    }
+    if ($item['below']) {
+      $trail = array_merge($trail, nice_menus_build_page_trail($item['below']));
+    }
+  }
+  return $trail;
+}
 
 /**
  * Builds the final nice menu.
@@ -257,7 +278,13 @@
 function theme_nice_menu_tree($menu_name, $mlid = NULL, $menu = NULL) {
   // Load the full menu array.
   $menu = isset($menu) ? $menu : menu_tree_all_data($menu_name);
-
+
+  if (isset($menu)) {
+    $page_menu = menu_tree_page_data($menu_name);
+    $trail = nice_menus_build_page_trail($page_menu);
+    unset($page_menu);
+  }
+  
   // For custom $menus and menus built all the way from the top-level we
   // don't need to "create" the specific sub-menu and we need to get the title
   // from the $menu_name since there is no "parent item" array.
@@ -287,7 +314,7 @@
   $output['subject'] = $title;
 
   if ($menu) {
-    $output['content'] .= theme('nice_menu_build', $menu);
+    $output['content'] .= theme('nice_menu_build', $menu, $trail);
   }
 
   return $output;
@@ -299,7 +326,7 @@
  * @param $menu
  *   Menu array from which to build the nested lists.
  */
-function theme_nice_menu_build($menu) {
+function theme_nice_menu_build($menu, $trail) {
   $output = '';
 
   foreach ($menu as $menu_item) {
@@ -316,10 +343,17 @@
       // If it has children build a nice little tree under it.
       if ((!empty($menu_item['link']['has_children'])) && (!empty($menu_item['below']))) {
         // Keep passing children into the function 'til we get them all.
-        $children = theme('nice_menu_build', $menu_item['below']);
+        $children = theme('nice_menu_build', $menu_item['below'], $trail);
         // Set the class to parent only of children are displayed.
-        $parent_class = $children ? 'menuparent ' : '';
-        $output .= '<li id="menu-'. $mlid .'" class="'. $parent_class . $path_class .'">'. theme('menu_item_link', $menu_item['link']);
+        $parent_class = $children ? 'menuparent ' : '';
+        // check if this item is in the active trail
+        if ($trail && in_array($mlid, $trail)) {
+          $trail_class = 'active-trail ';
+        }
+        else {
+          $trail_class = '';
+        }
+        $output .= '<li id="menu-'. $mlid .'" class="'. $parent_class . $trail_class . $path_class .'">'. theme('menu_item_link', $menu_item['link']);
         // Build the child UL only if children are displayed for the user.
         if ($children) {
           $output .= '<ul>';