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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


       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

       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