form_fieldtype()

NAME

new_fieldtype(), free_fieldtype(), set_fieldtype_arg(), set_fieldtype_choice() link_fieldtype form_field - define validation-field types

SYNOPSIS

#include <form.h>


FIELDTYPE *new_fieldtype(int (*field_check)(FIELD *, char *),
						 int (*char_check)(int, char *));
int free_fieldtype(FIELDTYPE *fieldtype);
in set_fieldtype_arg(FIELDTYPE *fieldtype
					 char *(*mak_arg)(va_list *),
					 char *(*copy_arg)(char *),
					 void (*free_arg)(char *));
in set_fieldtype_choice(FIELDTYPE *fieldtype
						int (*next_choice)(FIELD *, char *),
						int (*prev_choice)(FIELD *, char *));
FIELDTYPE *link_fieldtype(FIELDYPE *type1, FIELDTYPE *type2);

DESCRIPTION

The function new_fieldtype(3) creates a new field type usable for data validation. You supply it with field_check, a predicate to check the validity of an entered data string whenever the user attempt to leave a field. The (FIELD *) argument is passed in so the validation predicate can see the field's buffer, sizes and other attributes; the second argument is an argument-block structure, about which more below.

You also supply with char_check, a function to validate input characters as they are entered; it will be passed the character to be checked and a pointer to an argument-block structure.

The function free_fieldtype(3) frees the space allocated for a given validation type.

The function set_fieldtype(3) associates three storage-management functions with a field type. The mak_arg function is automatically applied to the list of arguments you give set_field_type(3) when attaching validation to a field; its job is to bundle these into an allocated argument-block object which can later be passed to validation predicated. The other two hook arguments should copy and free argument-block structures. They will be used by the forms-driver code.

The form driver requests REQ_NEXT_CHOICE and REQ_PREV_CHOICE assume that the possible values of a field form an ordered set, and provide the forms user with a way to move through the set. The set_fieldtype_choice(3) function allows forms programmers to define successor and predecessor functions for the field type. These functions take the field pointer and an argument-block structure as arguments.

RETURN VALUE

The character-pointer-valued routines return NULL on error.

The integer-valued routines return one of the following codes on error:

E_OK

The routine succeeded.

E_SYSTEM_ERROR

System error occurred (see errno

E_BAD_ARGUMENT

Routine detected an incorrect or out-of-range argument.

E_CONNECTED

The field is already connected to a form.

SEE ALSO

curses(3)

forms(3)

NOTES

The header file <form.h> automatically includes the header file <curses.h>.

All of the (char *) arguments of these functions should actually be (void *). The type has been left uncorrected for strict compatibility with System V.

PORTABILITY

These routines emulate the System V forms library. They were not supported on Version 7 or BSD versions.