#include	<stdio.h>
#include	<math.h>
#define	PI	3.141592654
#define	hmot(n)		hpos += n
#define	hgoto(n)	hpos = n
#define	vmot(n)		vgoto(vpos + n)

extern	int	hpos;
extern	int	vpos;
extern	int	size;
extern	short	*pstab;
extern	int	DX;	/* step size in x */
extern	int	DY;	/* step size in y */
extern	int	drawdot;	/* character to use when drawing */
extern	int	drawsize;	/* shrink point size by this facter */

#define	sgn(n)	((n > 0) ? 1 : ((n < 0) ? -1 : 0))
#define	abs(n)	((n) >= 0 ? (n) : -(n))
#define	arcmove(x,y)	{ hgoto(x); vmot(-vpos-(y)); }

void
drawline(int dx, int dy, char *s)	/* draw line from here to dx, dy using s */
{
	int xd, yd;
	float val, slope;
	int i, numdots;
	int dirmot, perp;
	int motincr, perpincr;
	int ohpos, ovpos, osize, ofont;
	float incrway;

	osize = size;
	setsize(t_size(pstab[osize-1] / drawsize));
	ohpos = hpos;
	ovpos = vpos;
	xd = dx / DX;
	yd = dy / DX;
	if (xd == 0) {
		numdots = abs (yd);
		motincr = DX * sgn (yd);
		for (i = 0; i < numdots; i++) {
			vmot(motincr);
			put1(drawdot);
		}
		vgoto(ovpos + dy);
		setsize(osize);
		return;
	}
	if (yd == 0) {
		numdots = abs (xd);
		motincr = DX * sgn (xd);
		for (i = 0; i < numdots; i++) {
			hmot(motincr);
			put1(drawdot);
		}
		hgoto(ohpos + dx);
		setsize(osize);
		return;
	}
	if (abs (xd) > abs (yd)) {
		val = slope = (float) xd/yd;
		numdots = abs (xd);
		dirmot = 'h';
		perp = 'v';
		motincr = DX * sgn (xd);
		perpincr = DX * sgn (yd);
	}
	else {
		val = slope = (float) yd/xd;
		numdots = abs (yd);
		dirmot = 'v';
		perp = 'h';
		motincr = DX * sgn (yd);
		perpincr = DX * sgn (xd);
	}
	incrway = sgn ((int) slope);
	for (i = 0; i < numdots; i++) {
		val -= incrway;
		if (dirmot == 'h')
			hmot(motincr);
		else
			vmot(motincr);
		if (val * slope < 0) {
			if (perp == 'h')
				hmot(perpincr);
			else
				vmot(perpincr);
			val += slope;
		}
		put1(drawdot);
	}
	hgoto(ohpos + dx);
	vgoto(ovpos + dy);
	setsize(osize);
}

drawwig(s)	/* draw wiggly line */
	char *s;
{
	int x[50], y[50], xp, yp, pxp, pyp;
	float t1, t2, t3, w;
	int i, j, steps, N, prevsteps;
	int osize, ofont;
	char temp[50], *p, *getstr();

	osize = size;
	setsize(t_size(pstab[osize-1] / drawsize));
	p = s;
	for (N = 2; (p=getstr(p,temp)) != NULL && N < sizeof(x)/sizeof(x[0]); N++) {
		x[N] = atoi(temp);
		p = getstr(p, temp);
		y[N] = atoi(temp);
	}
	x[0] = x[1] = hpos;
	y[0] = y[1] = vpos;
	for (i = 1; i < N; i++) {
		x[i+1] += x[i];
		y[i+1] += y[i];
	}
	x[N] = x[N-1];
	y[N] = y[N-1];
	prevsteps = 0;
	pxp = pyp = -9999;
	for (i = 0; i < N-1; i++) {	/* interval */
		steps = (dist(x[i],y[i], x[i+1],y[i+1]) + dist(x[i+1],y[i+1], x[i+2],y[i+2])) / 2;
		steps /= DX;
		for (j = 0; j < steps; j++) {	/* points within */
			w = (float) j / steps;
			t1 = 0.5 * w * w;
			w = w - 0.5;
			t2 = 0.75 - w * w;
			w = w - 0.5;
			t3 = 0.5 * w * w;
			xp = t1 * x[i+2] + t2 * x[i+1] + t3 * x[i] + 0.5;
			yp = t1 * y[i+2] + t2 * y[i+1] + t3 * y[i] + 0.5;
			if (xp != pxp || yp != pyp) {
				hgoto(xp);
				vgoto(yp);
				put1(drawdot);
				pxp = xp;
				pyp = yp;
			}
		}
	}
	setsize(osize);
}

char *getstr(p, temp)	/* copy next non-blank string from p to temp, update p */
char *p, *temp;
{
	while (*p == ' ' || *p == '\t' || *p == '\n')
		p++;
	if (*p == '\0') {
		temp[0] = 0;
		return(NULL);
	}
	while (*p != ' ' && *p != '\t' && *p != '\n' && *p != '\0')
		*temp++ = *p++;
	*temp = '\0';
	return(p);
}

drawcirc(d)
{
	int xc, yc;

	xc = hpos;
	yc = vpos;
	conicarc(hpos + d/2, -vpos, hpos, -vpos, hpos, -vpos, d/2, d/2);
	hgoto(xc + d);	/* circle goes to right side */
	vgoto(yc);
}

dist(x1, y1, x2, y2)	/* integer distance from x1,y1 to x2,y2 */
{
	float dx, dy;

	dx = x2 - x1;
	dy = y2 - y1;
	return sqrt(dx*dx + dy*dy) + 0.5;
}

drawarc(dx1, dy1, dx2, dy2)
{
	int x0, y0, x2, y2, r;

	x0 = hpos + dx1;	/* center */
	y0 = vpos + dy1;
	x2 = x0 + dx2;	/* "to" */
	y2 = y0 + dy2;
	r = sqrt((float) dx1 * dx1 + (float) dy1 * dy1) + 0.5;
	conicarc(x0, -y0, hpos, -vpos, x2, -y2, r, r);
}

drawellip(a, b)
{
	int xc, yc;

	xc = hpos;
	yc = vpos;
	conicarc(hpos + a/2, -vpos, hpos, -vpos, hpos, -vpos, a/2, b/2);
	hgoto(xc + a);
	vgoto(yc);
}

#define sqr(x) (long int)(x)*(x)

conicarc(x, y, x0, y0, x1, y1, a, b)
{
	/* based on Bresenham, CACM, Feb 77, pp 102-3 */
	/* by Chris Van Wyk */
	/* capitalized vars are an internal reference frame */
	long dotcount = 0;
	int osize, ofont;
	int	xs, ys, xt, yt, Xs, Ys, qs, Xt, Yt, qt,
		M1x, M1y, M2x, M2y, M3x, M3y,
		Q, move, Xc, Yc;
	int ox1, oy1;
	long	delta;
	float	xc, yc;
	float	radius, slope;
	float	xstep, ystep;

	osize = size;
	setsize(t_size(pstab[osize-1] / drawsize));
	ox1 = x1;
	oy1 = y1;
	if (a != b)	/* an arc of an ellipse; internally, will still think of circle */
		if (a > b) {
			xstep = (float)a / b;
			ystep = 1;
			radius = b;
		} else {
			xstep = 1;
			ystep = (float)b / a;
			radius = a;
		} 
	else {	/* a circular arc; radius is computed from center and first point */	
		xstep = ystep = 1;
		radius = sqrt((float)(sqr(x0 - x) + sqr(y0 - y)));
	}


	xc = x0;
	yc = y0;
	/* now, use start and end point locations to figure out
	the angle at which start and end happen; use these
	angles with known radius to figure out where start
	and end should be
	*/
	slope = atan2((double)(y0 - y), (double)(x0 - x) );
	if (slope == 0.0 && x0 < x)
		slope = 3.14159265;
	x0 = x + radius * cos(slope) + 0.5;
	y0 = y + radius * sin(slope) + 0.5;
	slope = atan2((double)(y1 - y), (double)(x1 - x));
	if (slope == 0.0 && x1 < x)
		slope = 3.14159265;
	x1 = x + radius * cos(slope) + 0.5;
	y1 = y + radius * sin(slope) + 0.5;
	/* step 2: translate to zero-centered circle */
	xs = x0 - x;
	ys = y0 - y;
	xt = x1 - x;
	yt = y1 - y;
	/* step 3: normalize to first quadrant */
	if (xs < 0)
		if (ys < 0) {
			Xs = abs(ys);
			Ys = abs(xs);
			qs = 3;
			M1x = 0;
			M1y = -1;
			M2x = 1;
			M2y = -1;
			M3x = 1;
			M3y = 0;
		} else {
			Xs = abs(xs);
			Ys = abs(ys);
			qs = 2;
			M1x = -1;
			M1y = 0;
			M2x = -1;
			M2y = -1;
			M3x = 0;
			M3y = -1;
		} 
	else if (ys < 0) {
		Xs = abs(xs);
		Ys = abs(ys);
		qs = 0;
		M1x = 1;
		M1y = 0;
		M2x = 1;
		M2y = 1;
		M3x = 0;
		M3y = 1;
	} else {
		Xs = abs(ys);
		Ys = abs(xs);
		qs = 1;
		M1x = 0;
		M1y = 1;
		M2x = -1;
		M2y = 1;
		M3x = -1;
		M3y = 0;
	}


	Xc = Xs;
	Yc = Ys;
	if (xt < 0)
		if (yt < 0) {
			Xt = abs(yt);
			Yt = abs(xt);
			qt = 3;
		} else {
			Xt = abs(xt);
			Yt = abs(yt);
			qt = 2;
		} 
	else if (yt < 0) {
		Xt = abs(xt);
		Yt = abs(yt);
		qt = 0;
	} else {
		Xt = abs(yt);
		Yt = abs(xt);
		qt = 1;
	}


	/* step 4: calculate number of quadrant crossings */
	if (((4 + qt - qs)
	     % 4 == 0)
	     && (Xt <= Xs)
	     && (Yt >= Ys)
	    )
		Q = 3;
	else
		Q = (4 + qt - qs) % 4 - 1;
	/* step 5: calculate initial decision difference */
	delta = sqr(Xs + 1)
	 + sqr(Ys - 1)
	-sqr(xs)
	-sqr(ys);
	/* here begins the work of drawing
   we hope it ends here too */
	while ((Q >= 0)
	     || ((Q > -2)
	     && ((Xt > Xc)
	     && (Yt < Yc)
	    )
	    )
	    ) {
		if (dotcount++ % DX == 0)
			putdot((int)xc, (int)yc);
		if (Yc < 0.5) {
			/* reinitialize */
			Xs = Xc = 0;
			Ys = Yc = sqrt((float)(sqr(xs) + sqr(ys)));
			delta = sqr(Xs + 1) + sqr(Ys - 1) - sqr(xs) - sqr(ys);
			Q--;
			M1x = M3x;
			M1y = M3y;
			 {
				int	T;
				T = M2y;
				M2y = M2x;
				M2x = -T;
				T = M3y;
				M3y = M3x;
				M3x = -T;
			}
		} else {
			if (delta <= 0)
				if (2 * delta + 2 * Yc - 1 <= 0)
					move = 1;
				else
					move = 2;
			else if (2 * delta - 2 * Xc - 1 <= 0)
				move = 2;
			else
				move = 3;
			switch (move) {
			case 1:
				Xc++;
				delta += 2 * Xc + 1;
				xc += M1x * xstep;
				yc += M1y * ystep;
				break;
			case 2:
				Xc++;
				Yc--;
				delta += 2 * Xc - 2 * Yc + 2;
				xc += M2x * xstep;
				yc += M2y * ystep;
				break;
			case 3:
				Yc--;
				delta -= 2 * Yc + 1;
				xc += M3x * xstep;
				yc += M3y * ystep;
				break;
			}
		}
	}


	setsize(osize);
	drawline((int)xc-ox1,(int)yc-oy1,".");
}

putdot(x, y)
{
	arcmove(x, y);
	put1(drawdot);
}
