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.\" Copyright \(co 2009 Red Hat, Inc.
.\"
.\" Permission is hereby granted, free of charge, to any person obtaining a
.\" copy of this software and associated documentation files (the "Software"),
.\" to deal in the Software without restriction, including without limitation
.\" the rights to use, copy, modify, merge, publish, distribute, sublicense,
.\" and/or sell copies of the Software, and to permit persons to whom the
.\" Software is furnished to do so, subject to the following conditions:
.\"
.\" The above copyright notice and this permission notice (including the next
.\" paragraph) shall be included in all copies or substantial portions of the
.\" Software.
.\"
.\" THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
.\" IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
.\" FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
.\" THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
.\" LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
.\" FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
.\" DEALINGS IN THE SOFTWARE.
.\"
.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
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.TH XGetEventData __libmansuffix__ __xorgversion__ "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
.Ds 0
.TA .5i 3i
.ta .5i 3i
typedef struct {
	int type;
	unsigned long serial;
	Bool send_event;
	Display *display;
	int extension;
	int evtype;
	unsigned int cookie;
	void *data;
} XGenericEventCookie;
.De

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

The
.ZN 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,
.ZN False
is returned. If
.ZN XGetEventData
returns
.ZN True ,
the cookie's data pointer points to the memory containing the event
information. A client must call
.ZN XFreeEventData
to free this memory.
.ZN XGetEventData
returns
.ZN False
for multiple calls for the same event cookie.

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

.SH EXAMPLE CODE
.Ds 0
.TA .5i 3i
.ta .5i 3i
XEvent event;
XGenericEventCookie *cookie = &ev;

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

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

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