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form_fieldtype 3x

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  predi-
       cate 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_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 predi-
       cated.  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_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

       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 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)