[gtk+] rbtree: Add _gtk_rbtree_contains()

[Benjamin Otte <otte src gnome org>]

commit 710a8435cce5511d8e7d0e441e3a079122076a6a
Author: Benjamin Otte <otte redhat com>
Date:   Sat Dec 10 02:02:29 2011 +0100

    rbtree: Add _gtk_rbtree_contains()
    
    It's useful in a bunch of places, so split it out

 gtk/gtkrbtree.c |   25 +++++++++++++++++++++++++
 gtk/gtkrbtree.h |    2 ++
 2 files changed, 27 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkrbtree.c b/gtk/gtkrbtree.c
index d6dc938..1b6d7f5 100644
--- a/gtk/gtkrbtree.c
+++ b/gtk/gtkrbtree.c
@@ -880,6 +880,31 @@ _gtk_rbtree_reorder (GtkRBTree *tree,
   g_free (nodes);
 }
 
+/**
+ * _gtk_rbtree_contains:
+ * @tree: a tree
+ * @potential_child: a potential child of @tree
+ *
+ * Checks if @potential_child is a child (direct or via intermediate
+ * trees) of @tree.
+ *
+ * Returns: %TRUE if @potentitial_child is a child of @tree.
+ **/
+gboolean
+_gtk_rbtree_contains (GtkRBTree *tree,
+                      GtkRBTree *potential_child)
+{
+  g_return_val_if_fail (tree != NULL, FALSE);
+  g_return_val_if_fail (potential_child != NULL, FALSE);
+
+  do {
+    potential_child = potential_child->parent_tree;
+    if (potential_child == tree)
+      return TRUE;
+  } while (potential_child != NULL);
+
+  return FALSE;
+}
 
 gint
 _gtk_rbtree_node_find_offset (GtkRBTree *tree,
diff --git a/gtk/gtkrbtree.h b/gtk/gtkrbtree.h
index 173b141..931f7c6 100644
--- a/gtk/gtkrbtree.h
+++ b/gtk/gtkrbtree.h
@@ -117,6 +117,8 @@ gboolean   _gtk_rbtree_is_nil           (GtkRBNode              *node);
 void       _gtk_rbtree_reorder          (GtkRBTree              *tree,
 					 gint                   *new_order,
 					 gint                    length);
+gboolean   _gtk_rbtree_contains         (GtkRBTree              *tree,
+                                         GtkRBTree              *potential_child);
 GtkRBNode *_gtk_rbtree_find_count       (GtkRBTree              *tree,
 					 gint                    count);
 void       _gtk_rbtree_node_set_height  (GtkRBTree              *tree,