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Off-Screen Pixel Map

Hello Macintosh and Lisp users,
  I am trying to realize drawing into an off-screen pixel map
in the MCL2.0b1 environment, as described for C and Pascal
in the Macintosh Technical Notes #120.

  But 'copybits' does not seem to work as it should. The pixels
are correct in the memory (which I checked with a simple
routine that interpretes bytes in memory as color pixels), but
I cannot produce them on the screen.

  This is the trouble statement in Pascal:
  CopyBits (BitMapPtr (MyCGrafPtr^.portPixMap^)^,
            bRect, destRect, 0, nil)

  This is my version in MCLisp:
  (#_CopyBits (rref MyCGrafPtr :cgrafport.portpixmap)
              (rref (wptr MyCWindow) :window.portBits)
              bRect destRect 0 (%null-ptr))

This statement only produces random black and white patterns,
a bitmap obviously.
Who has done such a 'copybits' call successfully in Lisp?
I would be relieved to get a reply!

Answers to:
Almut Herzog
F3.MMK (C5.019)
Postfach 12 40
W-St.Augustin 1
FR Germany

Tel.: Germany-2241-142872

E-Mail: wiba@f3svb.gmd.de

Thanks so much in advance, I am really close to despair!