XOpenDisplay(3X11) XLIB FUNCTIONS XOpenDisplay(3X11)
NAME
XOpenDisplay, XCloseDisplay - connect or disconnect to X
server
SYNTAX
Display *XOpenDisplay(char *display_name);
int XCloseDisplay(Display *display);
ARGUMENTS
display Specifies the connection to the X server.
display_name
Specifies the hardware display name, which deter-
mines 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.
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 con-
nects 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 informa-
tion macros or functions. For information about using macros
and functions to obtain information from the Display struc-
ture, 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, Pix-
map, Colormap, Cursor, and GContext), or other resources
XFree86 Version 4.5.0 1
XOpenDisplay(3X11) XLIB FUNCTIONS XOpenDisplay(3X11)
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.
SEE ALSO
AllPlanes(3X11), XFlush(3X11), XSetCloseDownMode(3X11)
Xlib - C Language X Interface
XFree86 Version 4.5.0 2