XOpenDisplay(XS)  X Version 11 (Release 5) 6 January 1993   XOpenDisplay(XS)


 Name

    XOpenDisplay - connect or disconnect to X server

 Syntax


    Display *XOpenDisplay(display_name)
          char *display_name;

    XCloseDisplay(display)
          Display *display;


 Arguments


    display        Specifies the connection to the X server.

    displayname   Specifies the hardware display name, which determines the
                   display and communications domain to be used.  On a
                   POSIX-conformant system, if the displayname is NULL, it
                   defaults to the value of the DISPLAY environment variable.

 Description

    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 speci-
    fied, 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 sin-
    gle X server can support any or all of these transport mechanisms simul-
    taneously.  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 of Xlib - C
    Language X Interface.

    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(XS)).  Therefore, these windows, resource IDs, and
    other resources should never be referenced again or an error will be gen-
    erated.  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.

 See also

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