#ifndef lint
static char sccsid[] = "@(#)arcs.c 9.2 88/01/19 Copyright 1985 Sun Micro";
#endif

/*
 * Copyright (c) 1985 by Sun Microsystems, Inc.
 */

/*-
	Routines to add arc segments to a path

	arcs.c, Thu Sep 19 18:09:49 1985

		Craig Taylor & James Gosling
		Sun Microsystems
 */


#ifdef REF
#include <sys/types.h>
#include <ref/config.h>
#endif
#include "cscript.h"

/*
 * Generate a circular arc: Pass in environment, operand stack and
 * counterclockwise flag.
 */
shape_arc(gc, x, y, r, a1, a2, ccw)
    register struct graphics_context *gc;
    fract       x,
                y,
                r,
                a1,
                a2;
{
    struct fpoint pa,
                pb,
                pc;
    register fract ae,
                v,
                p;
    register    scale = 0;

    /*
     * watch out for things like a1 = -180, a2 = 180
     */
    if (r <= 0)
	if (r == 0)
	    return;
	else {
	    r = -r;
	    ae = a2;
	    a2 = a1;
	    a1 = ae;
	}
    if (a1 == a2)
	return;

    /* Normalize the angles */
    if (floorfr(a1) > 360)
	a1 = a1 % fracti(360);
    if (floorfr(a2) > 360)
	a2 = a2 % fracti(360);
    while (r > fracti(127)) {
	scale++;
	r >>= 1;
    }
    while (a1 < 0)
	a1 += fracti(360);
    while (a2 < 0)
	a2 += fracti(360);
    /*
     * Prime the pump with the A point so that the remaining elements share
     * common endpoints at AC.
     */
    frsincosd(a1, &pc.y, &pc.x);
    pc.x = frmul(pc.x, r);
    pc.y = frmul(pc.y, r);
    if (cs_hascurrentpoint(gc))
	cs_frlineto(gc, (pc.x << scale) + x, (pc.y << scale) + y);
    else
	cs_frmoveto(gc, (pc.x << scale) + x, (pc.y << scale) + y);

    /* Generate ABC triangles in 90deg intervals */
    ae = a1;
    do {
	pa = pc;		/* Copy the common endpoint */
	if (fracti(90) <= (ccw ? (a1 < a2 ? a2 - a1 : fracti(360) + a2 - a1)
			   : (a2 < a1 ? a1 - a2 : fracti(360) + a1 - a2))) {
	    ae = a1 / fracti(90) * fracti(90) + fracti(ccw ? 90 : -90);
	    if (ae > fracti(360))
		ae = ae % fracti(360);
	    if (ae < 0)
		ae = fracti(360) + ae;
	}
	else
	    ae = a2;
	frsincosd(ae, &pc.y, &pc.x);
	pc.x = frmul(pc.x, r);
	pc.y = frmul(pc.y, r);
	p = ae - a1;
	if (abs(p) == fracti(90)) {
	    pb.x = pa.x + pc.x;
	    pb.y = pa.y + pc.y;
	    v = frrsh(FRSQRT2, 1);
	}
	else {
	    register fract denom;
	    denom = frmul(pa.x, pa.x + pc.x) + frmul(pa.y, pa.y + pc.y);
	    if (denom == 0)
		p = 0;
	    else
		p = frdiv(frmul(pa.x, pa.x) + frmul(pa.y, pa.y),
			  denom);
	    pb.x = frmul(p, pa.x + pc.x);
	    pb.y = frmul(p, pa.y + pc.y);
	    denom = frlsh(frsqrt(frsq(pa.x - pb.x)
				 + frsq(pa.y - pb.y)), 1);
	    if (denom == 0)
		v = 0;
	    else
		v = frdiv(frsqrt(frsq(pa.x - pc.x) + frsq(pa.y - pc.y)),
			  denom);
	}
	cs_frlineby(gc, (pb.x << scale) + x, (pb.y << scale) + y, v);
	cs_frlineto(gc, (pc.x << scale) + x, (pc.y << scale) + y);
	a1 = ae;
    } while (ae != a2);
}

cs_frarcto(gc, x2, y2, x3, y3, r, pxt1, pyt1, pxt2, pyt2)
    register struct graphics_context *gc;
    fract       x2,
                y2,
                x3,
                y3,
                r;
    fract      *pxt1,
               *pyt1,
               *pxt2,
               *pyt2;
{
    fract       xt1,
                yt1,
                xt2,
                yt2;

    /* if (!has_current_pos(&ee->path)) goto nocurrentpoint_error;  */
    sh_fritransform(&gc->transform, gc->currentpoint.x, gc->currentpoint.y);
    shape_point.x -= x2;
    shape_point.y -= y2;
    x3 -= x2;
    y3 -= y2;

    /* INRANGE(f) == -128.0<f<128.0 */
#define INRANGE(f) (((unsigned)((f)+fracti(128))) < fracti(256))

    if (INRANGE(shape_point.x)
	    && INRANGE(shape_point.y)
	    && INRANGE(x3)
	    && INRANGE(y3)) {
	fract       lp1,
	            lp3,
	            d;
	lp1 = frsqrt(frsq(shape_point.x) + frsq(shape_point.y));
	lp3 = frsqrt(frsq(x3) + frsq(y3));
	d = frmul(r, frsqrt(frdiv(frmul(lp1, lp3) + frmul(shape_point.x, x3)
				  + frmul(shape_point.y, y3),
				  frmul(lp1, lp3) - frmul(shape_point.x, x3)
				  - frmul(shape_point.y, y3))));
	xt1 = x2 + frdiv(frmul(d, shape_point.x), lp1);
	yt1 = y2 + frdiv(frmul(d, shape_point.y), lp1);
	xt2 = x2 + frdiv(frmul(d, x3), lp3);
	yt2 = y2 + frdiv(frmul(d, y3), lp3);
    }
    else {
	double      lp1,
	            lp3,
	            d;
	double      spx = floatfr(shape_point.x);
	double      spy = floatfr(shape_point.y);
	double      fx3 = floatfr(x3);
	double      fy3 = floatfr(y3);
	extern double sqrt();
	lp1 = sqrt(spx * spx + spy * spy);
	lp3 = sqrt(fx3 * fx3 + fy3 * fy3);
	d = floatfr(r) * sqrt((lp1 * lp3 + spx * fx3 + spy * fy3)
			      / (lp1 * lp3 - spx * fx3 - spy * fy3));
	xt1 = x2 + fractf(d * spx / lp1);
	yt1 = y2 + fractf(d * spy / lp1);
	xt2 = x2 + fractf(d * fx3 / lp3);
	yt2 = y2 + fractf(d * fy3 / lp3);
    }
    cs_frlineto(gc, xt1, yt1);
    cs_frlineby(gc, x2, y2, fracti(-1));	/* FIX SHARPNESS */
    cs_frlineto(gc, xt2, yt2);
    *pxt1 = xt1;
    *pyt1 = yt1;
    *pxt2 = xt2;
    *pyt2 = yt2;
}