on-demand in menu-item-container<%>
Called when the user clicks on the container as a menu bar (before the user sees any menu items), just before the container a as 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.
( -> voidsend a-menu-item-container on-demand)
Calls the demand-callback procedure that was provided when the
object was created, then calls the
on-demand method of the contained items.