.\" Copyright \(co 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1994 X Consortium
.\"
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.\" Copyright \(co 1985, 1986, 1987, 1988, 1989, 1990, 1991 by
.\" Digital Equipment Corporation
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.\" Portions Copyright \(co 1990, 1991 by
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.\" 
.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
.na
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.TH XOpenDisplay 3X11 "Release 6" "X Version 11" "XLIB FUNCTIONS"
.SH NAME
XOpenDisplay, XCloseDisplay \- connect or disconnect to X server
.SH SYNTAX
Display *XOpenDisplay\^(\^\fIdisplay_name\fP\^)
.br
      char *\fIdisplay_name\fP\^;
.LP
XCloseDisplay\^(\fIdisplay\fP\^)
.br
      Display *\fIdisplay\fP\^;
.SH ARGUMENTS
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIdisplay_name\fP 1i
Specifies the hardware display name, which determines the display
and communications domain to be used.
On a POSIX-conformant system, if the display_name is NULL, 
it defaults to the value of the DISPLAY environment variable. 
.IN "Environment" "DISPLAY"
.SH DESCRIPTION
The
.ZN XOpenDisplay
function returns a 
.ZN Display 
structure that serves as the
connection to the X server and that contains all the information
about that X server.
.ZN XOpenDisplay
connects your application to the X server through TCP 
or DECnet communications protocols,
or through some local inter-process communication protocol.
.IN "Protocol" "TCP"
.IN "Protocol" "DECnet"
If the hostname is a host machine name and a single colon (:)
separates the hostname and display number,
.ZN XOpenDisplay
connects using TCP streams.
If the hostname is not specified,
Xlib uses whatever it believes is the fastest transport.
If the hostname is a host machine name and a double colon (::)
separates the hostname and display number,
.ZN XOpenDisplay
connects using DECnet.
A single X server can support any or all of these transport mechanisms
simultaneously.
A particular Xlib implementation can support many more of these transport
mechanisms.
.LP
.IN "Display"
If successful, 
.ZN XOpenDisplay 
returns a pointer to a 
.ZN Display 
structure,
which is defined in 
.hN X11/Xlib.h .
If 
.ZN XOpenDisplay 
does not succeed, it returns NULL.
After a successful call to
.ZN XOpenDisplay ,
all of the screens in the display can be used by the client.
The screen number specified in the display_name argument is returned 
by the 
.ZN DefaultScreen
macro (or the
.ZN XDefaultScreen
function).
You can access elements of the
.ZN Display
and
.ZN Screen
structures only by using the information macros or functions.
For information about using macros and functions to obtain information from 
the
.ZN Display 
structure,
see section 2.2.1.
.LP
The
.ZN XCloseDisplay
function closes the connection to the X server for the display specified in the
.ZN Display
structure and destroys all windows, resource IDs
.Pn ( Window ,
.ZN Font ,
.ZN Pixmap ,
.ZN Colormap ,
.ZN Cursor ,
and
.ZN GContext ),
or other resources that the client has created
on this display, unless the close-down mode of the resource has been changed
(see
.ZN XSetCloseDownMode ).
Therefore, these windows, resource IDs, and other resources should never be 
referenced again or an error will be generated.
Before exiting, you should call
.ZN XCloseDisplay
explicitly so that any pending errors are reported as
.ZN XCloseDisplay
performs a final
.ZN XSync
operation.
.IN "Resource IDs"
.IN "XCloseDisplay"
.LP
.ZN XCloseDisplay
can generate a
.ZN BadGC
error.
.SH "SEE ALSO"
AllPlanes(3X11),
XFlush(3X11),
XSetCloseDownMode(3X11)
.br
\fI\*(xL\fP
