anchor.diff:  
     (defun register-event-listener (function)
       "not external"
  -    (funcall reg-event-callback-func function)))
  +	(if reg-event-callback-func
  +		(funcall reg-event-callback-func function)
  +		(push function event-callbacks-cache))))
   
   ;;----------------------------------------------------------------------
   
  
positive.code:   (defun set-register-event-callback-func (func)
      "Call this and pass the function that will be called when the cepl needs to
       query the window size"
      (setf reg-event-callback-func func))
  
    (defun set-make-gl-context-current-on-surface (func)
      "Call this and pass the function that will be called when the cepl needs to
  
negative.code: (let (step-func
        swap-func
        win-size-func
        (reg-event-callback-func nil)
  	  (event-callbacks-cache nil)
        (make-current-func (lambda (c s) c s)))
  
    (defun set-step-func (func)
  