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.\"***************************************************************************
.\" Copyright (c) 2008 Free Software Foundation, Inc.                        *
.\"                                                                          *
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.\"***************************************************************************
.\"
.\" $Id: curs_threads.3x,v 1.4 2008/01/19 23:29:24 tom Exp $
.TH curs_threads 3X ""
.na
.hy 0
.SH NAME
\fBuse_screen\fR,
\fBuse_window\fR - \fBcurses\fR thread support
.ad
.hy
.SH SYNOPSIS
\fB#include <curses.h>\fR
.sp
\fBtypedef int (*NCURSES_CALLBACK)(WINDOW *, void *);\fR
.br
\fBint set_escdelay(int size);\fR
.br
\fBint set_tabsize(int size);\fR
.br
\fBint use_screen(SCREEN *scr, NCURSES_CALLBACK func, void *data);\fR
.br
\fBint use_window(WINDOW *win, NCURSES_CALLBACK func, void *data);\fR
.br
.SH DESCRIPTION
This implementation can be configured to provide rudimentary support
for multi-threaded applications.
This makes a different set of libraries, e.g., \fIlibncursest\fP since
the binary interfaces are different.
.PP
Rather than modify the interfaces to pass a thread specifier to
each function, it adds a few functions which can be used in any
configuration which hide the mutex's needed to prevent concurrent
use of the global variables when configured for threading.
.PP
In addition to forcing access to members of the \fBWINDOW\fP structure
to be via functions (see \fBcurs_opaque\fP(3x)),
it makes functions of the common global variables,
e.g.,
COLORS,
COLOR_PAIRS,
COLS,
ESCDELAY,
LINES,
TABSIZE
curscr,
newscr and
ttytype.
Those variables are maintained as read-only values, stored in the \fBSCREEN\fP
structure.
.PP
Even this is not enough to make a thread-safe application using curses.
A multi-threaded application would be expected to have threads updating
separate windows (within the same device),
or updating on separate screens (on different devices).
Also, a few of the global variables are considered writable by some
applications.
The functions described here address these special situations.
.PP
The ESCDELAY and TABSIZE global variables are modified by some applications.
To modify them in any configuration,
use the \fBset_escdelay\fP or \fBset_tabsize\fP functions.
Other global variables are not modifiable.
.PP
The \fBuse_window\fP and \fBuse_screen\fP functions provide coarse
granularity mutexes for their respective \fBWINDOW\fP and \fBSCREEN\fP
parameters, and call a user-supplied function,
passing it a \fIdata\fP parameter,
and returning the value from the user-supplied function to the application.
.SH RETURN VALUE
These functions all return TRUE or FALSE, except as noted.
.SH NOTES
Both a macro and a function are provided for each name.
.SH PORTABILITY
These routines are specific to ncurses.
They were not supported on Version 7, BSD or System V implementations.
It is recommended that any code depending on ncurses extensions
be conditioned using NCURSES_VERSION.
.SH SEE ALSO
\fBcurses\fR(3X),
\fBcurs_opaque\fR(3X)
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