Index: ReferencedByFilter.module
===================================================================
--- ReferencedByFilter.module	(revision 6)
+++ ReferencedByFilter.module	(working copy)
@@ -25,6 +25,16 @@
       'help' => t('This argument allows views to query the nodes referenced by a certain node reference field.
         In the options field specify the referencing field.'),
     ),
+    'referencedbyfilter_selector' => array(
+      'name' => t('Node Reference: Field selector'),
+      'handler' => t('referencedbyfilter_arg_selector'),
+      'help' => t('This argument allows views to query the nodes referenced by a certain node reference field. Use in conjunction with the "Node Reference: views on selected node reference" argument.'),
+    ),
+    'referencedbyfilter_any' => array(
+      'name' => t('Node Reference: views on selected node reference'),
+      'handler' => t('referencedbyfilter_arg_any'),
+      'help' => t('This argument allows views to query the nodes referenced by the node reference field given by the selector field.'),
+    ),
   );
   return $arguments;
 }
@@ -80,4 +90,90 @@
     }
   }
   return $existing_reference_fields ;
-}
\ No newline at end of file
+}
+
+/**
+ * Handler for the selector: does nothing.
+ */
+function referencedbyfilter_arg_selector($op, &$query, $argtype, $arg = NULL) {
+  // do nothing.
+  // This argument is used by referencedbyfilter_arg_any.
+}
+
+/**
+ * Handler for the "any field" argument.
+ * Uses field set by the selector argument.
+ * Eg, if your content type has a field "myfield", then to get all the noderef nodes in that field,
+ * feed the view the args /myfield/NID
+ *
+ * This allows reuse of views.
+ */
+function referencedbyfilter_arg_any($op, &$query, $argtype, $arg = NULL) {
+  if ($op == 'filter') {
+
+    $nid = (int)$arg;
+    if (is_int($nid)) {
+      $selector_argument = _views_get_argument('referencedbyfilter_selector');
+      // Get field name from the selector argument. Clean user input!
+      $referencing_field = check_plain($selector_argument['value']);
+      $node_reference_table = 'content_'. $referencing_field;
+
+      // platform3 joachim:
+      // fixing bug where nodes that had no row for their noderef field produced all results,
+      // because a node_load here (WHY????) checked the field in the $node object.
+      /*
+      $node = node_load($nid);
+      if (!empty($node->$referencing_field)) {
+      */
+      $joininfo = array(
+        'type' => 'LEFT',
+        'left' => array(
+          'table' => 'node',
+          'field' => 'nid',
+        ),
+        'right' => array(
+          // Join to the referenced field.
+          'field' => $referencing_field .'_nid',
+        ),
+      );
+      $query->add_table($node_reference_table, FALSE, 1, $joininfo);
+      $query->add_field($referencing_field .'_nid', $node_reference_table);
+      $query->add_where($node_reference_table. '.nid = %d', $nid);
+      $vid=db_result(db_query("SELECT vid FROM {node} WHERE nid = %d", $nid));
+      $query->add_where($node_reference_table .'.vid = %d', $vid);
+    }
+  }
+}
+
+
+/**
+ * Helper function: retrieve the argument data from the current view, given the argument name.
+ * Eg: one argument needs to get data from a helper argument. We know what name it has
+ * but not what position.
+ *
+ * @return
+ *  A full argument array from the view object, with a value item added so no further
+ *  poking at the views object is necessary.
+ *  Eg:
+      vid (String, 2 characters ) 21
+      type (String, 27 characters ) referencedbyfilter_selector
+      argdefault (String, 1 characters ) 2
+      title (String, 0 characters )
+      options (String, 0 characters )
+      position (String, 1 characters ) 0
+      wildcard (String, 0 characters )
+      wildcard_substitution (String, 0 characters )
+      id (String, 27 characters ) referencedbyfilter_selector
+      value userinput
+ */
+function _views_get_argument($argument_name) {
+  $view = $GLOBALS['current_view'];
+
+  foreach ($view->argument as $position => $argument) {
+    if ($argument['type'] == $argument_name) {
+      $argument['value'] = $view->args[$argument['position']];
+
+      return $argument;
+    }
+  }
+}