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       XOpenDisplay, XCloseDisplay - connect or disconnect to X server


       Display *XOpenDisplay(char *display_name);

       int XCloseDisplay(Display *display);


       display   Specifies the connection to the X server.

                 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.


       The XOpenDisplay function returns a Display structure that serves as
       the connection to the X server and that contains all the information
       about that X server.  XOpenDisplay connects your application to the X
       server through TCP or DECnet communications protocols, or through some
       local inter-process communication protocol.  If the hostname is a host
       machine name and a single colon (:) separates the hostname and display
       number, 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, 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.

       If successful, XOpenDisplay returns a pointer to a Display structure,
       which is defined in <X11/Xlib.h>.  If XOpenDisplay does not succeed, it
       returns NULL.  After a successful call to 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 DefaultScreen
       macro (or the XDefaultScreen function).  You can access elements of the
       Display and Screen structures only by using the information macros or
       functions.  For information about using macros and functions to obtain
       information from the Display structure, see section 2.2.1.

       The XCloseDisplay function closes the connection to the X server for
       the display specified in the Display structure and destroys all
       windows, resource IDs (Window, Font, Pixmap, Colormap, Cursor, and
       GContext), or other resources that the client has created on this
       display, unless the close-down mode of the resource has been changed
       (see 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 XCloseDisplay explicitly so
       that any pending errors are reported as XCloseDisplay performs a final
       XSync operation.

       XCloseDisplay can generate a BadGC error.


       AllPlanes(3), XFlush(3), XSetCloseDownMode(3)
       Xlib - C Language X Interface