'\" t
.\"***************************************************************************
.\" Copyright 2018-2019,2020 Thomas E. Dickey                                *
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.\" $Id: form_field_buffer.3x,v 1.27 2020/10/24 09:27:17 tom Exp $
.TH form_field_buffer 3X ""
.ie \n(.g .ds `` \(lq
.el       .ds `` ``
.ie \n(.g .ds '' \(rq
.el       .ds '' ''
.de bP
.ie n  .IP \(bu 4
.el    .IP \(bu 2
..
.SH NAME
\fBform_field_buffer\fR \- field buffer control
.SH SYNOPSIS
\fB#include <form.h>\fR
.sp
\fBint set_field_buffer(FIELD *\fP\fIfield\fP\fB, int \fP\fIbuf\fP\fB, const char *\fP\fIvalue\fP\fB);\fP
.br
\fBchar *field_buffer(const FIELD *\fP\fIfield\fP\fB, int \fP\fIbuffer\fP\fB);\fP
.sp
\fBint set_field_status(FIELD *\fP\fIfield\fP\fB, bool \fP\fIstatus\fP\fB);\fP
.br
\fBbool field_status(const FIELD *\fP\fIfield\fP\fB);\fP
.sp
\fBint set_max_field(FIELD *\fP\fIfield\fP\fB, int \fP\fImax\fP\fB);\fP
.br
.SH DESCRIPTION
The function \fBset_field_buffer\fR sets the numbered buffer of the given field
to contain a given string:
.RS 3
.bP
Buffer 0 is the displayed value of the field.
.bP
Other numbered buffers may be allocated by applications through the \fBnbuf\fR
argument of (see \fBform_field_new\fR(3X))
but are not manipulated by the forms library.
.RE
.PP
The function \fBfield_buffer\fR returns a pointer to
the contents of the given numbered buffer:
.RS 3
.bP
The buffer contents always have the same length,
and are padded with trailing spaces
as needed to ensure this length is the same.
.bP
The buffer may contain leading spaces, depending on how it was set.
.bP
The buffer contents are set with \fBset_field_buffer\fP,
or as a side effect of any editing operations on the corresponding field.
.bP
Editing operations are based on the \fIwindow\fP which displays the field,
rather than a \fIstring\fP.
The window contains only printable characters, and is filled with blanks.
If you want the raw data, you must write your
own routine that copies the value out of the buffer and removes the leading
and trailing spaces.
.bP
Because editing operations change the content of the buffer to
correspond to the window, you should not rely on using buffers
for long-term storage of form data.
.RE
.PP
The function \fBset_field_status\fR sets the associated status flag of
\fIfield\fR; \fBfield_status\fR gets the current value.
The status flag
is set to a nonzero value whenever the field changes.
.PP
The function \fBset_max_field\fR sets the maximum size for a dynamic field.
An argument of 0 turns off any maximum size threshold for that field.
.SH RETURN VALUE
The \fBfield_buffer\fR function returns NULL on error.
It sets \fBerrno\fP according to their success:
.TP 5
.B E_OK
The routine succeeded.
.TP 5
.B E_BAD_ARGUMENT
Routine detected an incorrect or out-of-range argument.
.PP
The \fBfield_status\fR function returns \fBTRUE\fR or \fBFALSE\fR.
.PP
The remaining 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\fR(3)).
.TP 5
.B E_BAD_ARGUMENT
Routine detected an incorrect or out-of-range argument.
.SH SEE ALSO
\fBcurses\fR(3X) and related pages whose names begin \*(``form_\*('' for detailed
descriptions of the entry points.
.SH NOTES
The header file \fB<form.h>\fR automatically includes the header file
.PP
When configured for wide characters, \fBfield_buffer\fP returns a pointer
to temporary storage (allocated and freed by the library).
The application should not attempt to modify the data.
It will be freed on the next call to \fBfield_buffer\fP to return the
same buffer.
\fB<curses.h>\fR.
.SH PORTABILITY
These routines emulate the System V forms library.
They were not supported on
Version 7 or BSD versions.
.PP
The \fBset_max_field\fP function checks for an ncurses extension
\fBO_INPUT_FIELD\fP which allows a dynamic field to shrink if the new
limit is smaller than the current field size.
.SH AUTHORS
Juergen Pfeifer.
Manual pages and adaptation for new curses by Eric S. Raymond.