function theme_variables($widget, &$args) {
  global $widget_variables;

  if(!isset($widget_variables[$widget])) {
    // We can't use module_invoke since we need to pass a reference:
    foreach (module_implements('variables') as $module) {
      $function = $module . '_variables';
      $function($widget, $widget_variables[$widget]);
    }
  }

  $args += $widget_variables[$widget];
}