#ifndef lint
static const char	RCSid[] = "$Id: arc.c,v 1.3 2003/11/15 02:13:37 schorsch Exp $";
#endif

#include "local4014.h"
#include "lib4014.h"

int del = 20;

extern void
step(int d)
{
	del = d;
}

extern void
arc(
	int x,
	int y,
	int x0,
	int y0,
	int x1,
	int y1
)
{
	double pc;
	double sqrt();
	int flg,m,xc,yc,xs,ys,qs,qf;
	float dx,dy,r;
	char use;
	dx = x-x0;
	dy = y-y0;
	r = dx*dx+dy*dy;
	pc = r;
	pc = sqrt(pc);
	flg = pc/4;
	if(flg == 0)step(1);
	else if(flg < del)step(flg);
	xc = xs = x0;
	yc = ys = y0;
	move(xs,ys);
	if(x0 == x1 && y0 == y1)flg=0;
	else flg=1;
	qs = quad(x,y,x0,y0);
	qf = quad(x,y,x1,y1);
	if(abs_(x-x1) < abs_(y-y1)){
		use = 'x';
		if(qs == 2 || qs ==3)m = -1;
		else m=1;
	}
	else {
		use = 'y';
		if(qs > 2)m= -1;
		else m= 1;
	}
	while(1){
		switch(use){
		case 'x':	
			if(qs == 2 || qs == 3)yc -= del;
			else yc += del;
			dy = yc-y;
			pc = r-dy*dy;
			xc = m*sqrt(pc)+x;
			if((x < xs && x >= xc) || ( x > xs && x <= xc) ||
			    (y < ys && y >= yc) || ( y > ys && y <=  yc) )
			{
				if(++qs > 4)qs=1;
				if(qs == 2 || qs == 3)m= -1;
				else m=1;
				flg=1;
			}
			cont(xc,yc);
			xs = xc; 
			ys = yc;
			if(qs == qf && flg == 1)
				switch(qf){
				case 3:
				case 4:	
					if(xs >= x1)return;
					continue;
				case 1:
				case 2:
					if(xs <= x1)return;
				}
			continue;
		case 'y':	
			if(qs > 2)xc += del;
			else xc -= del;
			dx = xc-x;
			pc = r-dx*dx;
			yc = m*sqrt(pc)+y;
			if((x < xs && x >= xc) || ( x > xs && x <= xc ) ||
			    (y < ys && y >= yc) || (y > ys && y <= yc) )
			{
				if(++qs > 4)qs=1;
				if(qs > 2)m = -1;
				else m = 1;
				flg=1;
			}
			cont(xc,yc);
			xs = xc; 
			ys = yc;
			if(qs == qf && flg == 1)
				switch(qs){
				case 1:
				case 4:
					if(ys >= y1)return;
					continue;
				case 2:
				case 3:
					if(ys <= y1)return;
				}
		}
	}
}

extern int
quad(
	int x,
	int y,
	int xp,
	int yp
)
{
	if(x < xp)
		if(y <= yp)return(1);
		else return(4);
	else if(x > xp)
		if(y < yp)return(2);
		else return(3);
	else if(y < yp)return(2);
	else return(4);
}

extern int
abs_( /* Windows complains that abs() is an "internal function" */
	int a
)
{
	if(a < 0)return(-a);
	return(a);
}