radio-menu-item: Add join_group()

The other Radio* widgets have this convenience method that removes the
memory management of the opaque GSList used to handle the group from the
API usable from language bindings (especially the ones not based on
introspection).

This commit adds gtk_radio_menu_item_join_group().

https://bugzilla.gnome.org/show_bug.cgi?id=671362

demos/gtk-demo/menus.c

@@ -33,8 +33,7 @@ static GtkWidget *
 create_menu (gint     depth)
 {
   GtkWidget *menu;
-  GtkWidget *menuitem;
-  GSList *group;
+  GtkRadioMenuItem *last_item;
   char buf[32];
   int i, j;
 
@@ -42,20 +41,24 @@ create_menu (gint     depth)
     return NULL;
 
   menu = gtk_menu_new ();
-  group = NULL;
+  last_item = NULL;
 
   for (i = 0, j = 1; i < 5; i++, j++)
     {
+      GtkWidget *menu_item;
+
       sprintf (buf, "item %2d - %d", depth, j);
-      menuitem = gtk_radio_menu_item_new_with_label (group, buf);
-      group = gtk_radio_menu_item_get_group (GTK_RADIO_MENU_ITEM (menuitem));
 
-      gtk_menu_shell_append (GTK_MENU_SHELL (menu), menuitem);
-      gtk_widget_show (menuitem);
+      menu_item = gtk_radio_menu_item_new_with_label_from_widget (NULL, buf);
+      gtk_radio_menu_item_join_group (GTK_RADIO_MENU_ITEM (menu_item), last_item);
+      last_item = GTK_RADIO_MENU_ITEM (menu_item);
+
+      gtk_menu_shell_append (GTK_MENU_SHELL (menu), menu_item);
+      gtk_widget_show (menu_item);
       if (i == 3)
-        gtk_widget_set_sensitive (menuitem, FALSE);
+        gtk_widget_set_sensitive (menu_item, FALSE);
 
-      gtk_menu_item_set_submenu (GTK_MENU_ITEM (menuitem), create_menu (depth - 1));
+      gtk_menu_item_set_submenu (GTK_MENU_ITEM (menu_item), create_menu (depth - 1));
     }
 
   return menu;

docs/reference/gtk/gtk3-sections.txt

@@ -2771,6 +2771,7 @@ gtk_radio_menu_item_new_with_label_from_widget
 gtk_radio_menu_item_new_with_mnemonic_from_widget
 gtk_radio_menu_item_set_group
 gtk_radio_menu_item_get_group
+gtk_radio_menu_item_join_group
 <SUBSECTION Standard>
 GTK_RADIO_MENU_ITEM
 GTK_IS_RADIO_MENU_ITEM

gtk/gtkradiomenuitem.c

@@ -558,3 +558,59 @@ gtk_radio_menu_item_activate (GtkMenuItem *menu_item)
 
   gtk_widget_queue_draw (GTK_WIDGET (radio_menu_item));
 }
+
+/**
+ * gtk_radio_menu_item_join_group:
+ * @radio_menu_item: a #GtkRadioMenuItem
+ * @group_source: (allow-none): a #GtkRadioMenuItem whose group we are
+ *   joining, or %NULL to remove the @radio_menu_item from its current
+ *   group
+ *
+ * Joins a #GtkRadioMenuItem object to the group of another #GtkRadioMenuItem
+ * object.
+ *
+ * This function should be used by language bindings to avoid the memory
+ * manangement of the opaque #GSList of gtk_radio_menu_item_get_group()
+ * and gtk_radio_menu_item_set_group().
+ *
+ * A common way to set up a group of #GtkRadioMenuItem instances is:
+ *
+ * |[
+ *   GtkRadioMenuItem *last_item = NULL;
+ *
+ *   while ( ...more items to add... )
+ *     {
+ *       GtkRadioMenuItem *radio_item;
+ *
+ *       radio_item = gtk_radio_menu_item_new (...);
+ *
+ *       gtk_radio_menu_item_join_group (radio_item, last_item);
+ *       last_item = radio_item;
+ *     }
+ * ]|
+ *
+ * Since: 3.18
+ */
+void
+gtk_radio_menu_item_join_group (GtkRadioMenuItem *radio_menu_item,
+                                GtkRadioMenuItem *group_source)
+{
+  g_return_if_fail (GTK_IS_RADIO_MENU_ITEM (radio_menu_item));
+  g_return_if_fail (group_source == NULL || GTK_IS_RADIO_MENU_ITEM (group_source));
+
+  if (group_source != NULL)
+    {
+      GSList *group = gtk_radio_menu_item_get_group (group_source);
+
+      if (group == NULL)
+        {
+          /* if the group source does not have a group, we force one */
+          gtk_radio_menu_item_set_group (group_source, NULL);
+          group = gtk_radio_menu_item_get_group (group_source);
+        }
+
+      gtk_radio_menu_item_set_group (radio_menu_item, group);
+    }
+  else
+    gtk_radio_menu_item_set_group (radio_menu_item, NULL);
+}

gtk/gtkradiomenuitem.h

@@ -95,6 +95,10 @@ GDK_AVAILABLE_IN_ALL
 void       gtk_radio_menu_item_set_group                     (GtkRadioMenuItem *radio_menu_item,
 							      GSList           *group);
 
+GDK_AVAILABLE_IN_3_18
+void       gtk_radio_menu_item_join_group                    (GtkRadioMenuItem *radio_menu_item,
+                                                              GtkRadioMenuItem *group_source);
+
 G_END_DECLS
 
 #endif /* __GTK_RADIO_MENU_ITEM_H__ */