XGetEventData(3) XLIB FUNCTIONS XGetEventData(3)
NAME
XGetEventData, XFreeEventData, XGenericEventCookie - retrieve and
free additional event data through cookies.
SYNTAX
Bool XGetEventData(Display *
display, XGenericEventCookie *
cookie);
void XFreeEventData(Display *
display, XGenericEventCookie *
cookie);
ARGUMENTS
display Specifies the connection to the X server.
cookie Specifies the cookie to free or retrieve the data for.
STRUCTURES
typedef struct {
int type;
unsigned long serial;
Bool send_event;
Display *display;
int extension;
int evtype;
unsigned int cookie;
void *data;
} XGenericEventCookie;
DESCRIPTION
Some extension
XGenericEvents require additional memory to store
information. For these events, the library returns a
XGenericEventCookie with a token ('cookie') unique to this event.
The
XGenericEventCookie's data pointer is undefined until
XGetEventData is called.
The
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,
False is returned. If
XGetEventData returns
True, the cookie's data
pointer points to the memory containing the event information. A
client must call
XFreeEventData to free this memory.
XGetEventData returns
False for multiple calls for the same event cookie.
The
XFreeEventData function frees the data associated with a cookie.
A client must call
XFreeEventData for each cookie claimed with
XGetEventData.
EXAMPLE CODE
XEvent event;
XGenericEventCookie *cookie = &ev;
XNextEvent(display, &event);
if (XGetEventData(display, cookie)) {
handle_cookie_event(cookie->data);
} else
handle_event(&event);
}
XFreeEventData(display, cookie);
NOTES
A cookie is defined as unclaimed if it has been returned to the
client through
XNextEvent but its data has not been retrieved via
XGetEventData. Subsequent calls to
XNextEvent may free memory
associated with unclaimed cookies. Multi-threaded X clients must
ensure that
XGetEventData is called before the next call to
XNextEvent.
SEE ALSO
XNextEvent(3),
Xlib - C Language X InterfaceX Version 11 libX11 1.8.10 XGetEventData(3)
