XOpenDisplay(3) XLIB FUNCTIONS XOpenDisplay(3)
NAME
XOpenDisplay, XCloseDisplay - connect or disconnect to X server
SYNTAX
Display *XOpenDisplay(_Xconst char *display_name);
int XCloseDisplay(Display *display);
ARGUMENTS
display Specifies the connection to the X server.
display_name
Specifies the hardware display name, which determines the dis-
play and communications domain to be used. On a POSIX-confor-
mant system, if the display_name 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.
The XCloseDisplay function closes the connection to the X server for the
display specified in the Display structure and destroys all windows, re-
source 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 XSetCloseDown-
Mode). 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.
SEE ALSO
AllPlanes(3), XFlush(3), XSetCloseDownMode(3)
Xlib - C Language X Interface
X Version 11 libX11 1.8.12 XOpenDisplay(3)
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