A popup-menu% object is created without a parent. Dynamically display a popup-menu% with popup-menu in canvas<%>.
A popup menu is not a control, but a choice% control displays a single value that the user selects from a popup menu. A choice% control's popup menu is built into the control, and it is not accessible to the programmer.
If title is not #f, it is used as a displayed title at the top of the popup menu.
If title contains an ampersand (``&''), it is handled specially, the same as for menu% titles. A popup menu mnemonic is not useful, but it is supported for consistentcy with other menu labels.