anchor.diff:    (with-slots (fence lock) side
       (let ((fence (bt:with-recursive-lock-held (lock) fence)))
         (when fence
  -        (%gl:client-wait-sync fence :sync-flush-commands 1000000)))))
  +        (%gl:client-wait-sync fence :sync-flush-commands +default-fence-timeout+)))))
   
   
   (defun refresh-side-fence (side)
  
positive.code: (cl:in-package :cl-bodge.graphics)
  
  
  (defclass ping-pong-side ()
    ((object :initform nil :initarg :object :reader ping-pong-side-object)
  
negative.code: 
  (defun ping-pong-swap (object)
    (with-slots (front back) object
      (with-side-locked (back)
        (wait-for-side back)
       (with-side-locked (front)
          (wait-for-side front)
          (let ((tmp front))
            (setf front back
                  back tmp))))))
  