A Popup is a special sort of group. It has a collapsed state in which it doesn't show its children, but only its caption and/or graphic. The user can make the group "pop up" so that it shows its children.
Standard Properties
caption, children, enabled, height, left, look, numChildren, sizeHControl, sizeVControl, tile, tileHAlign, tileHInset, tileLayout, tileSpacing, tileVAlign, tileVInset, top, version, visible, width.
sizeHControl, sizeVControl: Only SIZE_AS_NEEDED and SIZE_AS_SPECIFIED will be supported. SIZE_AS_NEEDED will only be partially supported: when the component becomes visible and their height or width is zero, the component will size itself to a default value.
visible: Applies to the Popup's button, not to any menu window that gets created when this button is pressed.