anchor.diff:    (gl:ortho 0 1 0 1 -1 1)
     )
   
  +(setq color .7)
   (defmethod glut:display ((w wa-mask))
     (gl:clear :color-buffer)
  -  (gl:color .7 0 1)
  +  (gl:color color 0 1)
     (gl:with-primitive :polygon
       (gl:vertex 0.25 0.25 0)
  -    (gl:vertex 0.75 0.25 0)
  +    (gl:vertex .75 0.25 0)
       (gl:vertex 0.75 0.75 0)
       (gl:vertex 0.25 0.75 0))
     (gl:flush))
  
positive.code: 
  (defpackage #:wa
    (:use #:cl))
  (declaim (sb-ext:muffle-conditions cl:warning))
  (defun image-setup ()
    (setq quicklisp-reqs '(cl-glut bordeaux-threads bit-smasher))
    (mapcar (lambda (x) (ql:quickload x)) quicklisp-reqs))
  
  (defclass wa-mask
      (glut:window) ()
  
negative.code:    evdev-stream '()
     calibrate t)
  
  (setq pressure 0
     abs-x nil
     abs-y nil)
  
  (defun handle-pen (event)
    (with-slots (value type) event
      (let ((axis (cadr type)))
        
        (cond ((equal axis 'ABS_PRESSURE)
  	     (setq pressure value))
  	    ((equal axis 'ABS_X)
  	     (setq abs-x value))
  	    ((equal axis 'ABS_Y)
  	     (setq abs-y value)))
  
        (setq color .7)
        (if (> pressure 100)
  	  (setq color .5))
        (if (> pressure 200)
  	  (setq color 0))
        (glut:post-redisplay)
        )
      )  
    )
  
  (defun handle-scroll (event)
    (with-slots (value) event
      ;; (print value)   
      )
    nil
  )
  
  (defun process-wacom-stream ()
    (cl-evdev::with-evdev-device 
        (input "/dev/input/wacom")
      ;; (print input)
  
      (cond ((typep input 'relative-event)
  	   (handle-scroll input))
  	  ((typep input 'absolute-event)
  	   (handle-pen input))
  	  (t nil))    
      ))
  
  (defun debug-raw-evdev ()
    (with-open-file
        (stream  "/dev/input/tablet-graphire4-4x5"
  	       :direction :io
  	       :element-type '(unsigned-byte 8)
  	       :if-does-not-exist :error)
      (loop for x from 1 to 16 do ;; times
  	 (format t "~a " (read-byte stream nil)))
      (format t "~%~%")
      ))       
  
  (defun wa ()
    (bordeaux-threads:make-thread
     'process-wacom-stream :name "wacom-stream-process")
    (glut:display-window (make-instance 'wa-mask))
    )
  
  (defun compile-wa-image ()
  