define validation-field types 

Curses Function


#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. 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 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() 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() 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 formsdriver 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() 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 pointer-valued routines return NULL on error.

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


The routine succeeded.


System error occurred.


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


The field is already connected to a form.


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.


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.


PTC MKS Toolkit for Professional Developers
PTC MKS Toolkit for Enterprise Developers
PTC MKS Toolkit for Enterprise Developers 64-Bit Edition


curses(), form()

PTC MKS Toolkit 10.3 Documentation Build 39.