The Control Definition Function Resource
CHANGED WITH THE APPEARANCE MANAGER
In addition to the standard controls, the Control Manager allows you to define new, nonstandard controls as appropriate for your application. To define your own type of control, write a control definition function which is stored in a resource of type'CDEF'. Provide as the resource data the compiled or assembled code of your control definition procedure. The entry point of your procedure must be at the beginning of the resource data. See "Defining Your Own Control Definition Function" for more information about creating a control definition function.