/*  * This file is part of the UCB release of Plan 9. It is subject to the license * terms in the LICENSE file found in the top-level directory of this * distribution and at http://akaros.cs.berkeley.edu/files/Plan9License. No * part of the UCB release of Plan 9, including this file, may be copied, * modified, propagated, or distributed except according to the terms contained * in the LICENSE file. */ #include	<stdio.h>#include	<math.h>#include	"pic.h"#include	"y.tab.h" void arc_extreme(double, double, double, double, double, double);int quadrant(double x, double y); obj *arcgen(int type)	/* handles circular and (eventually) elliptical arcs */{	static double prevw = HT10;	static double prevh = HT5;	static double prevrad = HT2;	static int dtox[2][4] ={ 1, -1, -1, 1, 1, 1, -1, -1 };	static int dtoy[2][4] ={ 1, 1, -1, -1, -1, 1, 1, -1 };	static int dctrx[2][4] ={ 0, -1, 0, 1, 0, 1, 0, -1 };	static int dctry[2][4] ={ 1, 0, -1, 0, -1, 0, 1, 0 };	static int nexthv[2][4] ={ U_DIR, L_DIR, D_DIR, R_DIR, D_DIR, R_DIR, U_DIR, L_DIR };	double dx2, dy2, ht, phi, r, d;	int i, head, to, at, cw, invis, ddtype, battr;	obj *p, *ppos;	double fromx, fromy, tox, toy, fillval = 0;	Attr *ap; 	prevrad = getfval("arcrad");	prevh = getfval("arrowht");	prevw = getfval("arrowwid");	fromx = curx;	fromy = cury;	head = to = at = cw = invis = ddtype = battr = 0;	for (i = 0; i < nattr; i++) {		ap = &attr[i];		switch (ap->a_type) {		case TEXTATTR:			savetext(ap->a_sub, ap->a_val.p);			break;		case HEAD:			head += ap->a_val.i;			break;		case INVIS:			invis = INVIS;			break;		case HEIGHT:	/* length of arrowhead */			prevh = ap->a_val.f;			break;		case WIDTH:	/* width of arrowhead */			prevw = ap->a_val.f;			break;		case RADIUS:			prevrad = ap->a_val.f;			break;		case DIAMETER:			prevrad = ap->a_val.f / 2;			break;		case CW:			cw = 1;			break;		case FROM:	/* start point of arc */			ppos = ap->a_val.o;			fromx = ppos->o_x;			fromy = ppos->o_y;			break;		case TO:	/* end point of arc */			ppos = ap->a_val.o;			tox = ppos->o_x;			toy = ppos->o_y;			to++;			break;		case AT:	/* center of arc */			ppos = ap->a_val.o;			curx = ppos->o_x;			cury = ppos->o_y;			at = 1;			break;		case UP:			hvmode = U_DIR;			break;		case DOWN:			hvmode = D_DIR;			break;		case RIGHT:			hvmode = R_DIR;			break;		case LEFT:			hvmode = L_DIR;			break;		case FILL:			battr |= FILLBIT;			if (ap->a_sub == DEFAULT)				fillval = getfval("fillval");			else				fillval = ap->a_val.f;			break;		}	}	if (!at && !to) {	/* the defaults are mostly OK */		curx = fromx + prevrad * dctrx[cw][hvmode];		cury = fromy + prevrad * dctry[cw][hvmode];		tox = fromx + prevrad * dtox[cw][hvmode];		toy = fromy + prevrad * dtoy[cw][hvmode];		hvmode = nexthv[cw][hvmode];	}	else if (!at) {		dx2 = (tox - fromx) / 2;		dy2 = (toy - fromy) / 2;		phi = atan2(dy2, dx2) + (cw ? -PI/2 : PI/2);		if (prevrad <= 0.0)			prevrad = dx2*dx2+dy2*dy2;		for (r=prevrad; (d = r*r - (dx2*dx2+dy2*dy2)) <= 0.0; r *= 2)			;	/* this kludge gets around too-small radii */		prevrad = r;		ht = sqrt(d);		curx = fromx + dx2 + ht * cos(phi);		cury = fromy + dy2 + ht * sin(phi);		dprintf("dx2,dy2=%g,%g, phi=%g, r,ht=%g,%g\n",			dx2, dy2, phi, r, ht);	}	else if (at && !to) {	/* do we have all the cases??? */		tox = fromx + prevrad * dtox[cw][hvmode];		toy = fromy + prevrad * dtoy[cw][hvmode];		hvmode = nexthv[cw][hvmode];	}	if (cw) {	/* interchange roles of from-to and heads */		double temp;		temp = fromx; fromx = tox; tox = temp;		temp = fromy; fromy = toy; toy = temp;		if (head == HEAD1)			head = HEAD2;		else if (head == HEAD2)			head = HEAD1;	}	p = makenode(type, 7);	arc_extreme(fromx, fromy, tox, toy, curx, cury);	p->o_val[0] = fromx;	p->o_val[1] = fromy;	p->o_val[2] = tox;	p->o_val[3] = toy;	if (cw) {		curx = fromx;		cury = fromy;	} else {		curx = tox;		cury = toy;	}	p->o_val[4] = prevw;	p->o_val[5] = prevh;	p->o_val[6] = prevrad;	p->o_attr = head | (cw ? CW_ARC : 0) | invis | ddtype | battr;	p->o_fillval = fillval;	if (head)		p->o_nhead = getfval("arrowhead");	dprintf("arc rad %g at %g %g from %g %g to %g %g head %g %g\n",		prevrad, p->o_x, p->o_y,		p->o_val[0], p->o_val[1], p->o_val[2], p->o_val[3], p->o_val[4], p->o_val[5]);	return(p);} /***************************************************************************   bounding box of a circular arc             Eric Grosse  24 May 84 Conceptually, this routine generates a list consisting of the start,end, and whichever north, east, south, and west points lie on the arc.The bounding box is then the range of this list.    list = {start,end}    j = quadrant(start)    k = quadrant(end)    if( j==k && long way 'round )  append north,west,south,east    else      while( j != k )         append center+radius*[j-th of north,west,south,east unit vectors]         j += 1  (mod 4)    return( bounding box of list )The following code implements this, with simple optimizations.***********************************************************************/  void arc_extreme(double x0, double y0, double x1, double y1, double xc, double yc)			  /* start, end, center */{	/* assumes center isn't too far out */	double r, xmin, ymin, xmax, ymax;	int j, k;	x0 -= xc; y0 -= yc;	/* move to center */	x1 -= xc; y1 -= yc;	xmin = (x0<x1)?x0:x1; ymin = (y0<y1)?y0:y1;	xmax = (x0>x1)?x0:x1; ymax = (y0>y1)?y0:y1;	r = sqrt(x0*x0 + y0*y0);	if (r > 0.0) {		j = quadrant(x0,y0);		k = quadrant(x1,y1);		if (j == k && y1*x0 < x1*y0) {			/* viewed as complex numbers, if Im(z1/z0)<0, arc is big */			if( xmin > -r) xmin = -r; if( ymin > -r) ymin = -r;			if( xmax <  r) xmax =  r; if( ymax <  r) ymax =  r;		} else {			while (j != k) {				switch (j) {					case 1: if( ymax <  r) ymax =  r; break; /* north */					case 2: if( xmin > -r) xmin = -r; break; /* west */					case 3: if( ymin > -r) ymin = -r; break; /* south */					case 4: if( xmax <  r) xmax =  r; break; /* east */				}				j = j%4 + 1;			}		}	}	xmin += xc; ymin += yc;	xmax += xc; ymax += yc;	extreme(xmin, ymin);	extreme(xmax, ymax);} quadrant(double x, double y){	if (     x>=0.0 && y> 0.0) return(1);	else if( x< 0.0 && y>=0.0) return(2);	else if( x<=0.0 && y< 0.0) return(3);	else if( x> 0.0 && y<=0.0) return(4);	else			   return 0;	/* shut up lint */}