[plt-scheme] Problem to make background on a table game

Hi Scheme's users !

I started scheme this year and i would make a video poker for fun but
the bakcground is always white :s !!!
how can i change that ?

I try to use (make-background-region x y w h paint-callback)

but in paint-callback i use my canvas with the background and his dc
but i have

reference to undefined identifier: dc

Little part o my code :

(define image-fond (make-object bitmap% "images/background.jpg"
'jpeg))

(define canvas
  (new canvas% (parent t)
       (paint-callback
        (lambda (canvas dc)
          (send dc clear)
          (send dc draw-bitmap image-fond 0 0)))))

(define w (send t table-width))
(define h (send t table-height))

(make-background-region 0 0 w h (canvas dc)))


I hope you help me !!  See You :)