Added GtkBuilder support for "menu" child type of GtkMenuToolButton

docs/reference/gtk/tmpl/gtkmenutoolbutton.sgml

@@ -16,6 +16,24 @@ A GtkToolItem containing a button with an additional dropdown menu
   #GtkMenuToolButton. Use gtk_menu_tool_button_new_from_stock() to
   create a new #GtkMenuToolButton containing a stock item.
 </para>
+<refsect2 id="GtkMenuToolButton-BUILDER-UI">
+<title>GtkMenuToolButton as GtkBuildable</title>
+<para>
+The GtkMenuToolButton implementation of the GtkBuildable interface
+supports adding a menu by specifying "menu" as the "type" 
+attribute of a &lt;child&gt; element.
+</para>
+<example>
+<title>A UI definition fragment with menus</title>
+<programlisting><![CDATA[
+<object class="GtkMenuToolButton">
+  <child type="menu">
+    <object class="GtkMenu"/>
+  </child>
+</object>
+]]></programlisting>
+</example>
+</refsect2>
 
 <!-- ##### SECTION See_Also ##### -->
 <para>

gtk/gtkmenutoolbutton.c

@@ -30,6 +30,7 @@
 #include "gtkmenu.h"
 #include "gtkmain.h"
 #include "gtksizerequest.h"
+#include "gtkbuildable.h"
 
 #include "gtkprivate.h"
 #include "gtkintl.h"
@@ -49,6 +50,12 @@ static void gtk_menu_tool_button_destroy    (GtkWidget              *widget);
 static int  menu_deactivate_cb              (GtkMenuShell           *menu_shell,
 					     GtkMenuToolButton      *button);
 
+static void gtk_menu_tool_button_buildable_interface_init (GtkBuildableIface   *iface);
+static void gtk_menu_tool_button_buildable_add_child      (GtkBuildable        *buildable,
+							   GtkBuilder          *builder,
+							   GObject             *child,
+							   const gchar         *type);
+
 enum
 {
   SHOW_MENU,
@@ -63,7 +70,11 @@ enum
 
 static gint signals[LAST_SIGNAL];
 
-G_DEFINE_TYPE (GtkMenuToolButton, gtk_menu_tool_button, GTK_TYPE_TOOL_BUTTON)
+static GtkBuildableIface *parent_buildable_iface;
+
+G_DEFINE_TYPE_WITH_CODE (GtkMenuToolButton, gtk_menu_tool_button, GTK_TYPE_TOOL_BUTTON,
+                         G_IMPLEMENT_INTERFACE (GTK_TYPE_BUILDABLE,
+                                                gtk_menu_tool_button_buildable_interface_init))
 
 static void
 gtk_menu_tool_button_construct_contents (GtkMenuToolButton *button)
@@ -453,6 +464,26 @@ gtk_menu_tool_button_destroy (GtkWidget *widget)
   GTK_WIDGET_CLASS (gtk_menu_tool_button_parent_class)->destroy (widget);
 }
 
+static void
+gtk_menu_tool_button_buildable_add_child (GtkBuildable *buildable,
+					  GtkBuilder   *builder,
+					  GObject      *child,
+					  const gchar  *type)
+{
+  if (type && strcmp (type, "menu") == 0)
+    gtk_menu_tool_button_set_menu (GTK_MENU_TOOL_BUTTON (buildable),
+                                   GTK_WIDGET (child));
+  else
+    parent_buildable_iface->add_child (buildable, builder, child, type);
+}
+
+static void
+gtk_menu_tool_button_buildable_interface_init (GtkBuildableIface *iface)
+{
+  parent_buildable_iface = g_type_interface_peek_parent (iface);
+  iface->add_child = gtk_menu_tool_button_buildable_add_child;
+}
+
 /**
  * gtk_menu_tool_button_new:
  * @icon_widget: (allow-none): a widget that will be used as icon widget, or %NULL