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set_fieldtype_arg(3)

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 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 vali-
       dation type.

       The  function  set_fieldtype  associates three storage-management func-
       tions with a field type.  The mak_arg function is automatically applied
       to the list of arguments you give set_field_type when attaching valida-
       tion 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	struc-
       tures.  They will be used by the forms-driver code. You must supply the
       mak_arg function, the other two are optional, you may supply  NULL  for
       them.  In this case it is assumed, that mak_arg doesn't 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_field-
       type_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

       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(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 sup-
       ported on Version 7 or BSD versions.

AUTHORS

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

							    form_fieldtype(3X)

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