new_fieldtype() creates a new field type. The application programmer must write the function field_check, which validates the field value, and the function char_check, which validates each character. free_fieldtype() frees the space allocated for the field type.

By associating function pointers with a field type, set_fieldtype_arg() connects to the field type additional arguments necessary for a set_field_type() call. Function mak_arg allocates a structure for the field specific parameters to set_field_type() and returns a pointer to the saved data. Function copy_arg duplicates the structure created by make_arg. Function free_arg frees any storage allocated by make_arg or copy_arg.

The form_driver() requests REQ_NEXT_CHOICE and REQ_PREV_CHOICE let the user request the next or previous value of a field type comprising an ordered set of values. set_fieldtype_choice() allows the application programmer to implement these requests for the given field type. It associates with the given field type those application-defined functions that return pointers to the next or previous choice for the field.

link_fieldtype() returns a pointer to the field type built from the two given types. The constituent types may be any application-defined or pre-defined types.

Routines that return pointers always return NULL on error. Routines that return an integer return one of the following:

E_OK

The function returned successfully.

E_SYSTEM_ERROR

System error.

E_BAD_ARGUMENT

An argument is incorrect.

E_CONNECTED

Type is connected to one or more fields.

See attributes(5) for descriptions of the following attributes:

curses(3CURSES), forms(3CURSES), attributes(5)

The header <form.h> automatically includes the headers <eti.h> and <curses.h>.