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NAME
form_fieldtype - define validation-field types
SYNOPSIS
#include <form.h>
FIELDTYPE *new_fieldtype(
bool (* const field_check)(FIELD *, const void *),
bool (* const char_check)(int, const void *));
int free_fieldtype(FIELDTYPE *fieldtype);
int set_fieldtype_arg(
FIELDTYPE *fieldtype,
void *(* const make_arg)(va_list *),
void *(* const copy_arg)(const void *),
void (* const free_arg)(void *));
int set_fieldtype_choice(
FIELDTYPE *fieldtype,
bool (* const next_choice)(FIELD *, const void *),
bool (* const prev_choice)(FIELD *, const void *));
FIELDTYPE *link_fieldtype(FIELDTYPE *type1,
FIELDTYPE *type2);
DESCRIPTION
The function
new_fieldtype 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 attempts 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
new_fieldtype 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 frees the space allocated for a given
validation type.
The function
set_fieldtype_arg associates three storage-management functions
with a field type.
The
make_arg function is automatically applied to the
list of arguments you give
set_field_type 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.
You must supply the
make_arg function,
the other two are optional, you may supply NULL for them.
In this case it is assumed
that
make_arg does not allocate memory but simply loads the
argument into a single scalar value.
The function
link_fieldtype creates
a new field type from the two given types.
They are connected by an logical 'OR'.
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
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 pointer-valued routines return NULL on error.
The integer-valued routines return one of the following codes on
error:
5
E_OK
The routine succeeded.
5
E_SYSTEM_ERROR
System error occurred (see errno).
5
E_BAD_ARGUMENT
Routine detected an incorrect or out-of-range argument.
5
E_CONNECTED
The field is already connected to a form.
SEE ALSO
curses(3X),
form(3X).
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.
AUTHORS
Juergen Pfeifer. Manual pages and adaptation for new curses by Eric
S. Raymond.
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