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.ds xT X Toolkit Intrinsics \- C Language Interface
.ds xW Athena X Widgets \- C Language X Toolkit Interface
.ds xL Xlib \- C Language X Interface
.ds xC Inter-Client Communication Conventions Manual
.TH XGetEventData 3 "libX11 1.8.7" "X Version 11" "XLIB FUNCTIONS"
.SH NAME
XGetEventData, XFreeEventData, XGenericEventCookie \- retrieve and free additional event data through cookies.
.SH SYNTAX
.HP
Bool XGetEventData\^(\^Display *\fIdisplay\fP\^, XGenericEventCookie *\fIcookie\fP\^);
.HP
void XFreeEventData\^(\^Display *\fIdisplay\fP\^, XGenericEventCookie *\fIcookie\fP\^);
.HP
.SH ARGUMENTS
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcookie\fP 1i
Specifies the cookie to free or retrieve the data for.

.SH STRUCTURES
.EX
typedef struct {
        int type;
        unsigned long serial;
        Bool send_event;
        Display *display;
        int extension;
        int evtype;
        unsigned int cookie;
        void *data;
} XGenericEventCookie;
.EE

.SH DESCRIPTION
Some extension
.B XGenericEvents
require additional memory to store information.
For these events, the library returns a
.B XGenericEventCookie
with a token ('cookie') unique to this event.
The
.BR XGenericEventCookie 's
data pointer is undefined until
.B XGetEventData
is called.

The
.B XGetEventData
function retrieves this extra data for the given cookie.
No round-trip to
the server is required.
If the cookie is invalid or the
event is not an event handled by cookie handlers,
.B False
is returned.
If
.B XGetEventData
returns
.BR True ,
the cookie's data pointer points to the memory containing the event
information.
A client must call
.B XFreeEventData
to free this memory.
.B XGetEventData
returns
.B False
for multiple calls for the same event cookie.

The
.B XFreeEventData
function frees the data associated with a cookie.
A client must call
.B XFreeEventData
for each cookie claimed with
.BR XGetEventData .

.SH EXAMPLE CODE
.EX
XEvent event;
XGenericEventCookie *cookie = &ev;

XNextEvent(display, &event);
if (XGetEventData(display, cookie)) {
    handle_cookie_event(cookie->data);
} else
    handle_event(&event);
}
XFreeEventData(display, cookie);
.EE

.SH NOTES
A cookie is defined as unclaimed if it has been returned to the client
through
.B XNextEvent
but its data has not been retrieved via
.BR XGetEventData .
Subsequent calls to
.B XNextEvent
may free memory associated with unclaimed cookies.
Multi-threaded X clients must ensure that
.B XGetEventData
is called before the next call to
.BR XNextEvent .

.SH "SEE ALSO"
XNextEvent(3),
.br
\fI\*(xL\fP