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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
       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 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

       XCloseDisplay can generate a BadGC error.


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