[libdazzle] multi-paned: add helper to get nth widget

[Christian Hergert <chergert src gnome org>]

commit 68f9d8d6f5b4069bb64c5d1438675ba62afc322d
Author: Christian Hergert <chergert redhat com>
Date:   Wed Jun 21 23:02:44 2017 -0700

    multi-paned: add helper to get nth widget
    
    This is handy to get a widget knowing the index we care about.

 src/widgets/dzl-multi-paned.c |   25 +++++++++++++++++++++++++
 src/widgets/dzl-multi-paned.h |    2 ++
 2 files changed, 27 insertions(+), 0 deletions(-)
---
diff --git a/src/widgets/dzl-multi-paned.c b/src/widgets/dzl-multi-paned.c
index 2fe9f96..cec85a3 100644
--- a/src/widgets/dzl-multi-paned.c
+++ b/src/widgets/dzl-multi-paned.c
@@ -2159,3 +2159,28 @@ dzl_multi_paned_get_n_children (DzlMultiPaned *self)
 
   return priv->children ? priv->children->len : 0;
 }
+
+/**
+ * dzl_multi_paned_get_nth_child:
+ * @self: a #DzlMultiPaned
+ *
+ * Gets the @nth child of the #DzlMultiPaned.
+ *
+ * It is an error to call this function with a value >= the result of
+ * dzl_multi_paned_get_nth_child().
+ *
+ * The index starts from 0.
+ *
+ * Returns: (transfer none): A #GtkWidget
+ */
+GtkWidget *
+dzl_multi_paned_get_nth_child (DzlMultiPaned *self,
+                               guint          nth)
+{
+  DzlMultiPanedPrivate *priv = dzl_multi_paned_get_instance_private (self);
+
+  g_return_val_if_fail (DZL_IS_MULTI_PANED (self), NULL);
+  g_return_val_if_fail (nth < priv->children->len, NULL);
+
+  return g_array_index (priv->children, DzlMultiPanedChild, nth).widget;
+}
diff --git a/src/widgets/dzl-multi-paned.h b/src/widgets/dzl-multi-paned.h
index a5bc3c8..fa2fc94 100644
--- a/src/widgets/dzl-multi-paned.h
+++ b/src/widgets/dzl-multi-paned.h
@@ -53,6 +53,8 @@ struct _DzlMultiPanedClass
 
 GtkWidget *dzl_multi_paned_new            (void);
 guint      dzl_multi_paned_get_n_children (DzlMultiPaned *self);
+GtkWidget *dzl_multi_paned_get_nth_child  (DzlMultiPaned *self,
+                                           guint          nth);
 
 G_END_DECLS