GtkMenu::ensure_uline_accel_group
ensure_uline_accel_group() returns
the GtkAccelGroup used by GTK during the time
that the calling GtkMenu is popped up, if one
exists, and creates one for internal use if there is none.
This is currently the only way to get accelerators working properly
under win32. It is also used internally for popup menus in
GtkItemFactory. However, note that this method
has been eliminated from later versions of GTK+. The replacements in
GtkItemFactory are purely internal; the new
methods in GtkMenu are not.
