Polyfill: module{	PATH: con "/dis/math/polyfill.dis"; 	Zstate: adt{		r: Draw->Rect;		zbuf0, zbuf1: array of int;		xlen: int;		ylen: int;		xylen: int;	}; 	init: fn();	initzbuf: fn(r: Draw->Rect): ref Zstate;	clearzbuf: fn(s: ref Zstate);	setzbuf: fn(s: ref Zstate, zd: int);	fillpoly: fn(d: ref Image, v: array of Point, w: int, s: ref Image, p: Point, zstate: ref Zstate, dc, dx, dy: int);};