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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 infor- mation. For these events, the library returns a XGenericEventCookie with a token ('cookie') unique to this event. The XGenericEvent- Cookie'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 in- valid 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 XGetEvent- Data. 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 XGetEvent- Data. 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 Interface X Version 11 libX11 1.8.10 XGetEventData(3)