The following functions are intended as aids during development. In general they are not suitable for use in real applications, though they are fully supported.
The function contain takes an element argument and displays it. The element can be any pane, menu or a part of a menu, or a pinboard-object. Since displaying always requires an interface, contain creates an interface (unless the element is an interface itself). contain takes various keyword arguments that tell it how to display, and can also display the element as a dialog.
To create the interface, contain uses make-container, which can also be called directly.
CAPI User Guide and Reference Manual (Unix version) - 3 Aug 2017