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fieldtype(3form)


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.   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

   ncurses(3NCURSES), form(3FORM).

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.

                                                          fieldtype(3FORM)



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