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.\" $Id: form_hook.3x,v 1.39 2024/12/28 21:26:21 tom Exp $
.TH form_hook 3X 2024-12-28 "ncurses 6.5" "Library calls"
.SH NAME
\fBform_hook\fP \-
set hooks for automatic invocation by applications
.SH SYNOPSIS
.nf
\fB#include <form.h>
.PP
\fBint set_field_init(FORM *\fIform\fP, Form_Hook \fIfunc\fP);
\fBForm_Hook field_init(const FORM *\fIform\fP);
.PP
\fBint set_field_term(FORM *\fIform\fP, Form_Hook \fIfunc\fP);
\fBForm_Hook field_term(const FORM *\fIform\fP);
.PP
\fBint set_form_init(FORM *\fIform\fP, Form_Hook \fIfunc\fP);
\fBForm_Hook form_init(const FORM *\fIform\fP);
.PP
\fBint set_form_term(FORM *\fIform\fP, Form_Hook \fIfunc\fP);
\fBForm_Hook form_term(const FORM *\fIform\fP);
.fi
.SH DESCRIPTION
These functions make it possible to set hook functions to be called at various
points in the automatic processing of input event codes by \fBform_driver\fP.
.SS set_field_init
sets a hook to be called at form-post time
and each time the selected field changes (after the change).
.SS field_init
returns the current field init hook, if any
.RI ( NULL
if there is no such hook).
.SS set_field_term
sets a hook to be called at form-unpost time
and each time the selected field changes (before the change).
.SS field_term
returns the current field term hook, if any
.RI ( NULL
if there is no such hook).
.SS set_form_init
sets a hook to be called at form-post time and
just after a page change once it is posted.
.SS form_init
returns the current form init hook,
if any
.RI ( NULL
if there is no such hook).
.SS set_form_term
sets a hook to be called at form-unpost time
and just before a page change once it is posted.
.SS form_term
returns the current form term hook, if any
.RI ( NULL
if there is no such hook).
.SH RETURN VALUE
Routines that return pointers return
.I NULL
on error.
Other routines
return one of the following:
.TP 5
.B E_OK
The routine succeeded.
.TP 5
.B E_SYSTEM_ERROR
System error occurred (see \fBerrno\fP(3)).
.SH PORTABILITY
These routines emulate the System V forms library.
They were not supported on
Version 7 or BSD versions.
.SH AUTHORS
Juergen Pfeifer.
Manual pages and adaptation for new curses by Eric S. Raymond.
.SH SEE ALSO
\fB\%curses\fP(3X),
\fB\%form\fP(3X)