void gtk_menu_item_set_right_justified ( GtkMenuItem* menu_item, gboolean right_justified )
Sets whether the menu item appears justified at the right side of a menu bar. This was traditionally done for “Help” menu items, but is now considered a bad idea. (If the widget layout is reversed for a right-to-left language like Hebrew or Arabic, right-justified-menu-items appear at the left.)
Deprecated since: 3.2
If you insist on using it, use
gtk_widget_set_hexpand() and gtk_widget_set_halign().