https://invisible-island.net/ncurses/man/
form_fieldtype(3x) Library calls form_fieldtype(3x)
form_fieldtype - define validation-field types
#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);
The function new_fieldtype creates a new field type usable for data
validation. Its parameters are function pointers:
field_check
This function checks the validity of an entered data string
whenever the user attempts to leave a field. It has two
arguments:
o The (FIELD *) argument is passed in so the validation
predicate can see the field's buffer, sizes and other
attributes.
o The second argument is an argument-block structure, about
which more below.
char_check
This function validates input characters as they are entered. The
form library passes it the character to be checked and a pointer
to an argument-block structure.
The free_fieldtype function frees the space allocated for a given
validation type by new_fieldtype.
The function set_fieldtype_arg associates three storage-management
functions with a field type:
make_arg
This function is automatically applied to the list of arguments
you give set_field_type when attaching validation to a field. It
stores the arguments in an allocated argument-block object which
is used when validating input.
copy_arg
This function may be used by applications to copy argument-blocks.
free_arg
Frees an argument-block structure.
You must supply the make_arg function. The other two are optional: you
may supply NULL for them. In this case, the form library assumes that
make_arg does not allocate memory but simply loads the argument into a
single scalar value.
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.
The function link_fieldtype creates a new field type from the two given
types. They are connected by an logical 'OR'.
The pointer-valued routines return NULL on error. They set errno
according to their success:
E_OK The routine succeeded.
E_BAD_ARGUMENT
Routine detected an incorrect or out-of-range argument.
E_SYSTEM_ERROR
System error occurred, e.g., malloc failure.
The integer-valued routines return one of the following codes on error:
E_OK The routine succeeded.
E_BAD_ARGUMENT
Routine detected an incorrect or out-of-range argument.
E_CONNECTED
The field is already connected to a form.
E_CURRENT
The field is the current field.
E_SYSTEM_ERROR
System error occurred (see errno(3)).
These routines emulate the System V forms library. They were not
supported on Version 7 or BSD versions.
Juergen Pfeifer. Manual pages and adaptation for new curses by Eric S.
Raymond.
curses(3x), form(3x), form_field_validation(3x)
ncurses 6.5 2024-03-16 form_fieldtype(3x)