anchor.diff:    
   (let ((reader (reader-function 'event-type)))
     (defun %event-class (location)
  -    (gethash (funcall reader location 0) *event-classes*)))
  +    (or
  +     (gethash (funcall reader location 0) *event-classes*)
  +     (error "No class defined for event type: ~S" (funcall reader location 0)))))
   
   (defmethod make-proxy-instance :around ((class event-class) location 
   					&rest initargs)
  
positive.code: ;; TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
  ;; SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  
  ;; $Id: gdkevents.lisp,v 1.13 2008-01-07 16:02:23 espen Exp $
  
  (in-package "GDK")
  
  
negative.code:   (:metaclass event-class)
    (:event-type :owner-change))
  
  (defclass grab-broken-event (event)
    ((keyboard
      :allocation :alien
      :accessor event-keyboard
      :initarg :keyboard
      :type boolean)
     (implicit
      :allocation :alien
      :accessor event-implicit
      :initarg :implicit
      :type boolean))
    (:metaclass event-class)
    (:event-type :grab-broken))
  