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- connect or disconnect to X server
- Display *XOpenDisplay(char *display_name);
- int XCloseDisplay(Display *display);
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.
- 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
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
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
XCloseDisplay can generate a BadGC error.
Xlib - C Language X Interface
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