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 Interface

X Version 11							   libX11 1.5.0 						  XGetEventData(3)