NAME
       ChangeVPBitMap -- change display memory address for multi-buffered
                          animation (V39)

   SYNOPSIS
       ChangeVPBitMap(vp,bm,db)
                       a0 a1 a2

        void ChangeVPBitMap(struct viewport *, struct bitmap *, struct dbufinfo *);

   FUNCTION
        Changes the area of display memory which will be displayed in a
        viewport. This can be used to implement double (or triple)
        buffering, a method of achieving smooth animation.

   INPUTS
        vp  =  a pointer to a viewport
       bm  = a pointer to a bitmap structure. this bitmap structure must be
              of the same layout as the one attached to the viewport (same
              depth, alignment, and BytesPerRow).
        db  =  A pointer to a dbufinfo.

   BUGS

   NOTES
        This will set the vp->RasInfo->BitMap field to the bm pointer which is
        passed.

        When using the synchronization features, you MUST carefully insure that
        all messages have been replied to before calling freedbufinfo or
        calling ChangeVPBitMap with the same dbufinfo.


   SEE ALSO
        allocdbufinfo() allocbitmap()