Table of Contents
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. 
- display_name
- 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(3X11)
,
XFlush(3X11)
, XSetCloseDownMode(3X11)
 
Xlib - C Language X Interface 
Table of Contents