{
	int n, dx, dy, sx, pp_inc_1, pp_inc_2;
	register int a;
	register PIXEL *pp;
#if defined(INTERP_RGB)
	register unsigned int r, g, b;
#endif
#ifdef INTERP_RGB
	register unsigned int rinc, ginc, binc;
#endif
#ifdef INTERP_Z
	register unsigned int *pz;
	int zinc;
	register unsigned int z;
#endif

	if (p1->y > p2->y || (p1->y == p2->y && p1->x > p2->x)) {
		ZBufferPoint *tmp;
		tmp = p1;
		p1 = p2;
		p2 = tmp;
	}
	sx = zb->xsize;
	pp = (PIXEL *)((char *) zb->pbuf.getRawBuffer() + zb->linesize * p1->y + p1->x * PSZB);
#ifdef INTERP_Z
	pz = zb->zbuf + (p1->y * sx + p1->x);
	z = p1->z;
#endif

	dx = p2->x - p1->x;
	dy = p2->y - p1->y;
#ifdef INTERP_RGB
	r = p2->r << 8;
	g = p2->g << 8;
	b = p2->b << 8;
#endif

#ifdef INTERP_RGB
#define RGB(x) x
#define RGBPIXEL *pp = RGB_TO_PIXEL(r >> 8,g >> 8,b >> 8)
#else // INTERP_RGB
#define RGB(x)
#define RGBPIXEL *pp = color
#endif // INTERP_RGB

#ifdef INTERP_Z
#define ZZ(x) x
#define PUTPIXEL() 									\
	{												\
		if (ZCMP(z, *pz)) {							\
			RGBPIXEL;								\
			*pz = z; 								\
		}											\
	}
#else // INTERP_Z
#define ZZ(x)
#define PUTPIXEL() RGBPIXEL
#endif // INTERP_Z

#define DRAWLINE(dx, dy, inc_1, inc_2)	\
	n = dx;								\
	ZZ(zinc = (p2->z - p1->z)/n);		\
	RGB(rinc=((p2->r - p1->r) << 8)/n;	\
		ginc=((p2->g - p1->g) << 8)/n;	\
		binc=((p2->b - p1->b) << 8)/n);	\
	a = 2 * dy - dx;					\
	dy = 2 * dy;						\
	dx = 2 * dx - dy;					\
	pp_inc_1 = (inc_1) * PSZB;			\
	pp_inc_2 = (inc_2) * PSZB;			\
	do {								\
		PUTPIXEL();						\
		ZZ(z += zinc);					\
		RGB(r += rinc; g += ginc; b += binc); \
		if (a > 0) {					\
			pp = (PIXEL *)((char *)pp + pp_inc_1); \
			ZZ(pz+=(inc_1));			\
			a -= dx;					\
		} else {						\
			pp = (PIXEL *)((char *)pp + pp_inc_2); \
			ZZ(pz += (inc_2)); \
			a += dy; \
		} \
	} while (--n >= 0);

// fin macro

    if (dx == 0 && dy == 0) {
		PUTPIXEL();
    } else if (dx > 0) {
		if (dx >= dy) {
			DRAWLINE(dx, dy, sx + 1, 1);
		} else {
			DRAWLINE(dy, dx, sx + 1, sx);
		}
    } else {
		dx = -dx;
		if (dx >= dy) {
			DRAWLINE(dx, dy, sx - 1, -1);
		} else {
			DRAWLINE(dy, dx, sx - 1, sx);
		}
    }
}

#undef INTERP_Z
#undef INTERP_RGB

// internal defines
#undef DRAWLINE
#undef PUTPIXEL
#undef ZZ
#undef RGB
#undef RGBPIXEL