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XOpenDisplay(3) XLIB FUNCTIONS XOpenDisplay(3)
XOpenDisplay, XCloseDisplay - connect or disconnect to X server
Display *XOpenDisplay(_Xconst char *display_name);
int XCloseDisplay(Display *display);
display Specifies the connection to the X server.
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
XCloseDisplay can generate a BadGC error.
AllPlanes(3), XFlush(3), XSetCloseDownMode(3)
Xlib - C Language X Interface
X Version 11 libX11 1.7.2 XOpenDisplay(3)