(send a-menu-item-container get-items) → (listof (is-a?/c menu-item<%>))
Returns a list of the items in the menu, popup menu, or menu bar. The
order of the items in the returned list corresponds to the order as
the user sees them in the menu or menu bar.
Specification:
Called when the user clicks on the container as a menu bar (before the
user sees any menu items), just before the container as a popup menu
is popped up, or just before inspecting the menu bar containing the
item for a shortcut key binding.
If the container is not a menu bar or a popup menu, this method is normally called via the on-demand method of the container’s owning menu bar or popup menu, because the default implementation of the method chains to the on-demand method of its items. However, the method can be overridden in a container such that it does not call the on-demand method of its items.
Default implementation:
Calls the demand-callback procedure that was provided when
the object was created, then calls the on-demand method of the contained items.