anchor.diff:                (did-something-p nil))
             (labels ((fun (xs)
   		     (cond ((null xs)
  -                          ;; We reached the queue's tail: Append the new event, construct a new
  -                          ;; one if necessary.
  +                          ;; We reached the queue's tail: Append the
  +                          ;; new event, construct a new one if
  +                          ;; necessary.
                             (when did-something-p
                               (setf item
                                 (make-instance 'window-repaint-event
  
positive.code:   (with-slots (queue) sheet
      (event-queue-listen queue)))
  
  ;;;;
  
  ;;; Support for callers that want to set an event queue for every pane.
  
  (defclass no-event-queue-mixin ()
  
negative.code:   (declare (ignore predicate))
    (do-port-force-output eq))
  
  ;;; STANDARD-SHEET-INPUT-MIXIN
  
  (defclass standard-sheet-input-mixin ()
    ((queue :initform (make-instance 'port-event-queue)
  