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researchv9-SUN3(old)

#ifndef	MUX
#define	Jcursinhibit()	cursinhibit()
#define	Jcursallow()	cursallow()
#define	lrectf(l, r, f)	rectf(l, r, f)
#define	lsegment(l, p, q, f)	segment(l, p, q, f)
#endif

#include	<CC/jerq.h>
#define HUGE 017777777777
#define	sgn(x)	((x)<0? -1 : (x)==0? 0 : 1)

#ifdef	MUX
#define	POINT	Ivoid(26)	/* really lpoint, but we're dealing with the cursor */
#else
extern void point();
#define	POINT	point
#endif

static struct dist {
	Point s;
	Point m;
	long e;
} d1, d2;

static void
test(Point x, register struct dist *p)
{
	register long dx = x.x - p->s.x;
	register long dy = x.y - p->s.y;
	register long e = dx*dx+dy*dy;

	if(e <= p->e) {
		p->m = x;
		p->e = e;
	}
}

static void
survey(Bitmap *, Point x, Code)
{
	test(x, &d1);
	test(x, &d2);
}

static long emask, enext;

static void
paint(Bitmap *bp, Point x, Code f)
{
	if(enext&emask) POINT(bp, x, f);
	enext <<= 1;
	if(enext == 0) enext = 1;
}

/*
 * elarc(bp,p0,a,b,p1,p2,f) draws in bitmap bp an arc of the ellipse
 * centered at p0 with half-axes a,b extending counterclockwise
 * from a point near p1 to a point near p2
 * args reversed because ellip1 draws clockwise 
 */
extern void
elarc(Bitmap *bp, Point p0, int a, int b, Point p1, Point p2, Code f, long mask)
{
	short inhibited;

	emask = mask;
	enext = 1;
	inhibited=0;
	if(f!=F_XOR){
		Jcursinhibit();
		inhibited=1;
	}
	if(a==0)
		lsegment(bp, Pt(p0.x, p1.y), Pt(p0.x, p2.y), f);
	else if(b==0)
		lsegment(bp, Pt(p1.x, p0.y), Pt(p2.x, p0.y), f);
	else {
		int sx1;
		int sy1;
		int sx2;
		int sy2;

		d1.s = sub(p1, p0);
		d2.s = sub(p2, p0);
		sx1 = sgn(d1.s.x);
		sy1 = sgn(d1.s.y);
		sx2 = sgn(d2.s.x);
		sy2 = sgn(d2.s.y);
		d1.s.x *= sx1;
		d1.s.y *= sy1;
		d2.s.x *= sx2;
		d2.s.y *= sy2;
		d1.e = d2.e = HUGE;
		survey(bp, Pt(0, b), f);
		ellip1(bp, Pt(0, 0), a, b, survey, Pt(0,b), Pt(a, 0), f);
		if(d1.m != d2.m)
			paint(bp, d1.m, f);
		ellip1(bp, p0, a, b, paint,
			Pt(d1.m.x*sx1, d1.m.y*sy1), Pt(d2.m.x*sx2, d2.m.y*sy2), f);
	}
	if(inhibited)
		Jcursallow();
}

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