NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | SEE ALSO | NOTES | PORTABILITY | AUTHORS | COLOPHON

form_fieldtype(3X)                                        form_fieldtype(3X)

NAME         top

       form_fieldtype - define validation-field types

SYNOPSIS         top

       #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         top

       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         top

       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         top

       curses(3X), form(3X).

NOTES         top

       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         top

       These routines emulate the System V forms library.  They were not
       supported on Version 7 or BSD versions.

AUTHORS         top

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

COLOPHON         top

       This page is part of the ncurses (new curses) project.  Information
       about the project can be found at 
       ⟨https://www.gnu.org/software/ncurses/ncurses.html⟩.  If you have a
       bug report for this manual page, send it to
       bug-ncurses-request@gnu.org.  This page was obtained from the
       project's upstream Git mirror of the CVS repository
       ⟨git://ncurses.scripts.mit.edu/ncurses.git⟩ on 2017-11-25.  (At that
       time, the date of the most recent commit that was found in the repos‐
       itory was 2017-11-19.)  If you discover any rendering problems in
       this HTML version of the page, or you believe there is a better or
       more up-to-date source for the page, or you have corrections or
       improvements to the information in this COLOPHON (which is not part
       of the original manual page), send a mail to man-pages@man7.org

                                                          form_fieldtype(3X)