.\" Copyright \(co 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1994 X Consortium
.\"
.\" Permission is hereby granted, free of charge, to any person obtaining
.\" a copy of this software and associated documentation files (the
.\" "Software"), to deal in the Software without restriction, including
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.\" distribute, sublicense, and/or sell copies of the Software, and to
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.\" the following conditions:
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.\" The above copyright notice and this permission notice shall be included
.\" in all copies or substantial portions of the Software.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
.\" OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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.\" OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
.\" ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
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.\"
.\" Except as contained in this notice, the name of the X Consortium shall
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.\"
.\" Copyright \(co 1985, 1986, 1987, 1988, 1989, 1990, 1991 by
.\" Digital Equipment Corporation
.\"
.\" Portions Copyright \(co 1990, 1991 by
.\" Tektronix, Inc.
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.\" Permission to use, copy, modify and distribute this documentation for
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.\" It is provided ``as is'' without express or implied warranty.
.\" 
.ds xT X Toolkit Intrinsics \- C Language Interface
.ds xW Athena X Widgets \- C Language X Toolkit Interface
.ds xL Xlib \- C Language X Interface
.ds xC Inter-Client Communication Conventions Manual
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.TH XInitThreads 3X11 "Release 6" "X Version 11" "XLIB FUNCTIONS"
.SH NAME
XInitThreads, XLockDisplay, XUnlockDisplay \- multi-threading support
.SH SYNTAX
Status XInitThreads\^(\|);
.LP
void XLockDisplay\^(\^\fIdisplay\fP\^)
.br
      Display *\fIdisplay\fP\^;
.LP
void XUnlockDisplay\^(\^\fIdisplay\fP\^)
.br
      Display *\fIdisplay\fP\^;
.SH ARGUMENTS
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.SH DESCRIPTION
The
.ZN XInitThreads
function initializes Xlib support for concurrent threads.
This function must be the first Xlib function a
multi-threaded program calls, and it must complete
before any other Xlib call is made.
This function returns a nonzero status if initialization was
successful; otherwise, it returns zero.
On systems that do not support threads, this function always returns zero.
.LP
It is only necessary to call this function if multiple threads
might use Xlib concurrently.  If all calls to Xlib functions
are protected by some other access mechanism (for example,
a mutual exclusion lock in a toolkit or through explicit client
programming), Xlib thread initialization is not required.
It is recommended that single-threaded programs not call this function.

.LP
The
.ZN XLockDisplay
function locks out all other threads from using the specified display.
Other threads attempting to use the display will block until
the display is unlocked by this thread.
Nested calls to
.ZN XLockDisplay
work correctly; the display will not actually be unlocked until
.ZN XUnlockDisplay
has been called the same number of times as
.ZN XLockDisplay .
This function has no effect unless Xlib was successfully initialized
for threads using
.ZN XInitThreads .
.LP
The
.ZN XUnlockDisplay
function allows other threads to use the specified display again.
Any threads that have blocked on the display are allowed to continue.
Nested locking works correctly; if
.ZN XLockDisplay
has been called multiple times by a thread, then
.ZN XUnlockDisplay
must be called an equal number of times before the display is
actually unlocked.
This function has no effect unless Xlib was successfully initialized
for threads using
.ZN XInitThreads .
.SH "SEE ALSO"
\fI\*(xL\fP
