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form_fieldtype(3X)                                                                        form_fieldtype(3X)



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  argu-ments. arguments.
       ments.

RETURN VALUE
       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).

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  ver-sions. versions.
       sions.

AUTHORS
       Juergen Pfeifer.  Manual pages and adaptation for new curses by Eric S. Raymond.



                                                                                          form_fieldtype(3X)