XOpenDisplay(3X11) SysV XOpenDisplay(3X11)
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