Defines new classes of
define-layout is used to create new classes of layout. The macro is essentially the same as
defclass except that its default superclass is layout.
To implement a new class of layout, methods need to be provided for the following generic functions:
Translate the layout's child descriptions.
Calculate the constraints for the layout.
Layout the children of the layout.
CAPI User Guide and Reference Manual (Unix version) - 3 Aug 2017