anchor.diff:            (setf (mem-aref l :long 2) 0))))  
         (x-send-event dpy (x-default-root-window dpy) nil (foreign-bitfield-value 'x-event-mask-flags '(:structure-notify-mask)) msg))))
   
  -(defun x-open-display (display-name)
  +(defun x-open-display (&optional (display-name (null-pointer)))
     (let ((display (%x-open-display display-name)))
       (when (null-pointer-p display)
         (error "Unable to open display"))
  
positive.code:     (with-foreign-slots ((visual-id visual depth) visual-infos visual-info)
        (let ((colormap (x-create-color-map dpy root-win visual :alloc-none)))
          (with-foreign-object (win-attrs 'set-window-attributes)
            (with-foreign-slots ((cmap event-mask) win-attrs set-window-attributes)
              (setf cmap colormap
                    event-mask (foreign-bitfield-value 'x-event-mask-flags
                                  '(:exposure-mask
  
negative.code:                                   :button-press-mask :button-release-mask
                                    :structure-notify-mask
                                    :visibility-change-mask
                                    :pointer-motion-mask))
                    border-pixel 0)
              (%x-create-window dpy parent 0 0 width height 0
                                depth :input-output visual
                                '(:cw-colormap :cw-event-mask)
  