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()