X Version 11 (1 September 1988) XOpenDisplay(XS)
NAME
XOpenDisplay, XCloseDisplay - 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.
display_name
Specifies the hardware display name, which
determines the display and communications domain
to be used. On a UNIX-based 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, UNIX
domain, or DECnet communications protocols. 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 unix and a single colon (:)
separates it from the display number, XOpenDisplay connects
using UNIX domain IPC 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.
SEE ALSO
Xlib - C Language X Interface
(printed 2/12/90) (1 September 1988) XOpenDisplay(XS)