<oPopUp>:isOpen() --> lIsOpen

        Returns a logical value that indicates whether the pop-up menu is
        open or not.  A value of true (.T.) indicates that the pop-up menu is
        open, a value of false (.F.) indicates that it is closed.

        isOpen() is a method of the PopUpMenu class that is used for
        determining if a pop-up menu is open.  A pop-up menu is considered
        open during the period after calling its open() method and before
        calling its close() method