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