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