/* $Id$ $Revision$ */
/* vim:set shiftwidth=4 ts=8: */

/*************************************************************************
 * Copyright (c) 2011 AT&T Intellectual Property 
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors: See CVS logs. Details at http://www.graphviz.org/
 *************************************************************************/


#include "render.h"

#define EPSILON .0001

/* standard arrow length in points */
#define ARROW_LENGTH 10.

#define NUMB_OF_ARROW_HEADS  4
/* each arrow in 8 bits.  Room for NUMB_OF_ARROW_HEADS arrows in 32 bit int. */

#define BITS_PER_ARROW 8

#define BITS_PER_ARROW_TYPE 4
/* arrow types (in BITS_PER_ARROW_TYPE bits) */
#define ARR_TYPE_NONE	  (ARR_NONE)
#define ARR_TYPE_NORM	  1
#define ARR_TYPE_CROW	  2
#define ARR_TYPE_TEE	  3
#define ARR_TYPE_BOX	  4
#define ARR_TYPE_DIAMOND  5
#define ARR_TYPE_DOT      6
#define ARR_TYPE_CURVE    7
#define ARR_TYPE_GAP      8
/* Spare: 9-15 */

/* arrow mods (in (BITS_PER_ARROW - BITS_PER_ARROW_TYPE) bits) */
#define ARR_MOD_OPEN      (1<<(BITS_PER_ARROW_TYPE+0))
#define ARR_MOD_INV       (1<<(BITS_PER_ARROW_TYPE+1))
#define ARR_MOD_LEFT      (1<<(BITS_PER_ARROW_TYPE+2))
#define ARR_MOD_RIGHT     (1<<(BITS_PER_ARROW_TYPE+3))
/* No spares */

typedef struct arrowdir_t {
    char *dir;
    int sflag;
    int eflag;
} arrowdir_t;

static arrowdir_t Arrowdirs[] = {
    {"forward", ARR_TYPE_NONE, ARR_TYPE_NORM},
    {"back", ARR_TYPE_NORM, ARR_TYPE_NONE},
    {"both", ARR_TYPE_NORM, ARR_TYPE_NORM},
    {"none", ARR_TYPE_NONE, ARR_TYPE_NONE},
    {(char *) 0, ARR_TYPE_NONE, ARR_TYPE_NONE}
};

typedef struct arrowname_t {
    char *name;
    int type;
} arrowname_t;

static arrowname_t Arrowsynonyms[] = {
    /* synonyms for deprecated arrow names - included for backward compatibility */
    /*  evaluated before primary names else "invempty" would give different results */
    {"invempty", (ARR_TYPE_NORM | ARR_MOD_INV | ARR_MOD_OPEN)},	/* oinv     */
    {(char *) 0, (ARR_TYPE_NONE)}
};

static arrowname_t Arrowmods[] = {
    {"o", ARR_MOD_OPEN},
    {"r", ARR_MOD_RIGHT},
    {"l", ARR_MOD_LEFT},
    /* deprecated alternates for backward compat */
    {"e", ARR_MOD_OPEN},	/* o  - needed for "ediamond" */
    {"half", ARR_MOD_LEFT},	/* l  - needed for "halfopen" */
    {(char *) 0, ARR_TYPE_NONE}
};

static arrowname_t Arrownames[] = {
    {"normal", ARR_TYPE_NORM},
    {"crow", ARR_TYPE_CROW},
    {"tee", ARR_TYPE_TEE},
    {"box", ARR_TYPE_BOX},
    {"diamond", ARR_TYPE_DIAMOND},
    {"dot", ARR_TYPE_DOT},
//    {"none", ARR_TYPE_NONE},
    {"none", ARR_TYPE_GAP},
//    {"gap", ARR_TYPE_GAP},
    /* ARR_MOD_INV is used only here to define two additional shapes
       since not all types can use it */
    {"inv", (ARR_TYPE_NORM | ARR_MOD_INV)},
    {"vee", (ARR_TYPE_CROW | ARR_MOD_INV)},
    /* WARNING ugly kludge to deal with "o" v "open" conflict */
    /* Define "open" as just "pen" since "o" already taken as ARR_MOD_OPEN */
    /* Note that ARR_MOD_OPEN has no meaning for ARR_TYPE_CROW shape */
    {"pen", (ARR_TYPE_CROW | ARR_MOD_INV)},
    /* WARNING ugly kludge to deal with "e" v "empty" conflict */
    /* Define "empty" as just "mpty" since "e" already taken as ARR_MOD_OPEN */
    /* Note that ARR_MOD_OPEN has expected meaning for ARR_TYPE_NORM shape */
    {"mpty", ARR_TYPE_NORM},
    {"curve", ARR_TYPE_CURVE},
    {"icurve", (ARR_TYPE_CURVE | ARR_MOD_INV)},
    {(char *) 0, ARR_TYPE_NONE}
};

typedef struct arrowtype_t {
    int type;
    double lenfact;		/* ratio of length of this arrow type to standard arrow */
    void (*gen) (GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);	/* generator function for type */
} arrowtype_t;

/* forward declaration of functions used in Arrowtypes[] */
static void arrow_type_normal(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
static void arrow_type_crow(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
static void arrow_type_tee(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
static void arrow_type_box(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
static void arrow_type_diamond(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
static void arrow_type_dot(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
static void arrow_type_curve(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);
static void arrow_type_gap(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag);

static arrowtype_t Arrowtypes[] = {
    {ARR_TYPE_NORM, 1.0, arrow_type_normal},
    {ARR_TYPE_CROW, 1.0, arrow_type_crow},
    {ARR_TYPE_TEE, 0.5, arrow_type_tee},
    {ARR_TYPE_BOX, 1.0, arrow_type_box},
    {ARR_TYPE_DIAMOND, 1.2, arrow_type_diamond},
    {ARR_TYPE_DOT, 0.8, arrow_type_dot},
    {ARR_TYPE_CURVE, 1.0, arrow_type_curve},
    {ARR_TYPE_GAP, 0.5, arrow_type_gap},
    {ARR_TYPE_NONE, 0.0, NULL}
};

static char *arrow_match_name_frag(char *name, arrowname_t * arrownames, int *flag)
{
    arrowname_t *arrowname;
    size_t namelen = 0;
    char *rest = name;

    for (arrowname = arrownames; arrowname->name; arrowname++) {
	namelen = strlen(arrowname->name);
	if (strncmp(name, arrowname->name, namelen) == 0) {
	    *flag |= arrowname->type;
	    rest += namelen;
	    break;
	}
    }
    return rest;
}

static char *arrow_match_shape(char *name, int *flag)
{
    char *next, *rest;
    int f = ARR_TYPE_NONE;

    rest = arrow_match_name_frag(name, Arrowsynonyms, &f);
    if (rest == name) {
	do {
	    next = rest;
	    rest = arrow_match_name_frag(next, Arrowmods, &f);
	} while (next != rest);
	rest = arrow_match_name_frag(rest, Arrownames, &f);
    }
    if (f && !(f & ((1 << BITS_PER_ARROW_TYPE) - 1)))
	f |= ARR_TYPE_NORM;
    *flag |= f;
    return rest;
}

static void arrow_match_name(char *name, int *flag)
{
    char *rest = name;
    char *next;
    int i, f;

    *flag = 0;
    for (i = 0; *rest != '\0' && i < NUMB_OF_ARROW_HEADS; ) {
	f = ARR_TYPE_NONE;
	next = rest;
        rest = arrow_match_shape(next, &f);
	if (f == ARR_TYPE_NONE) {
	    agerr(AGWARN, "Arrow type \"%s\" unknown - ignoring\n", next);
	    return;
	}
	if (f == ARR_TYPE_GAP && i == (NUMB_OF_ARROW_HEADS -1))
	    f = ARR_TYPE_NONE;
	if ((f == ARR_TYPE_GAP) && (i == 0) && (*rest == '\0'))
	    f = ARR_TYPE_NONE;
	if (f != ARR_TYPE_NONE)
	    *flag |= (f << (i++ * BITS_PER_ARROW));
    }
}

void arrow_flags(Agedge_t * e, int *sflag, int *eflag)
{
    char *attr;
    arrowdir_t *arrowdir;

    *sflag = ARR_TYPE_NONE;
    *eflag = agisdirected(agraphof(e)) ? ARR_TYPE_NORM : ARR_TYPE_NONE;
    if (E_dir && ((attr = agxget(e, E_dir)))[0]) {
	for (arrowdir = Arrowdirs; arrowdir->dir; arrowdir++) {
	    if (streq(attr, arrowdir->dir)) {
		*sflag = arrowdir->sflag;
		*eflag = arrowdir->eflag;
		break;
	    }
	}
    }
    if (E_arrowhead && (*eflag == ARR_TYPE_NORM) && ((attr = agxget(e, E_arrowhead)))[0])
	arrow_match_name(attr, eflag);
    if (E_arrowtail && (*sflag == ARR_TYPE_NORM) && ((attr = agxget(e, E_arrowtail)))[0])
	arrow_match_name(attr, sflag);
    if (ED_conc_opp_flag(e)) {
	edge_t *f;
	int s0, e0;
	/* pick up arrowhead of opposing edge */
	f = agfindedge(agraphof(aghead(e)), aghead(e), agtail(e));
	arrow_flags(f, &s0, &e0);
	*eflag = *eflag | s0;
	*sflag = *sflag | e0;
    }
}

double arrow_length(edge_t * e, int flag)
{
    arrowtype_t *arrowtype;
    double lenfact = 0.0;
    int f, i;

    for (i = 0; i < NUMB_OF_ARROW_HEADS; i++) {
        /* we don't simply index with flag because arrowtypes are not necessarily sorted */
        f = (flag >> (i * BITS_PER_ARROW)) & ((1 << BITS_PER_ARROW_TYPE) - 1);
        for (arrowtype = Arrowtypes; arrowtype->gen; arrowtype++) {
	    if (f == arrowtype->type) {
	        lenfact += arrowtype->lenfact;
	        break;
	    }
        }
    }
    /* The original was missing the factor E_arrowsz, but I believe it
       should be here for correct arrow clipping */
    return ARROW_LENGTH * lenfact * late_double(e, E_arrowsz, 1.0, 0.0);
}

/* inside function for calls to bezier_clip */
static boolean inside(inside_t * inside_context, pointf p)
{
    return DIST2(p, inside_context->a.p[0]) <= inside_context->a.r[0];
}

int arrowEndClip(edge_t* e, pointf * ps, int startp,
		 int endp, bezier * spl, int eflag)
{
    inside_t inside_context;
    pointf sp[4];
    double elen, elen2;

    elen = arrow_length(e, eflag);
    elen2 = elen * elen;
    spl->eflag = eflag, spl->ep = ps[endp + 3];
    if (endp > startp && DIST2(ps[endp], ps[endp + 3]) < elen2) {
	endp -= 3;
    }
    sp[3] = ps[endp];
    sp[2] = ps[endp + 1];
    sp[1] = ps[endp + 2];
    sp[0] = spl->ep;	/* ensure endpoint starts inside */

    inside_context.a.p = &sp[0];
    inside_context.a.r = &elen2;
    bezier_clip(&inside_context, inside, sp, TRUE);

    ps[endp] = sp[3];
    ps[endp + 1] = sp[2];
    ps[endp + 2] = sp[1];
    ps[endp + 3] = sp[0];
    return endp;
}

int arrowStartClip(edge_t* e, pointf * ps, int startp,
		   int endp, bezier * spl, int sflag)
{
    inside_t inside_context;
    pointf sp[4];
    double slen, slen2;

    slen = arrow_length(e, sflag);
    slen2 = slen * slen;
    spl->sflag = sflag, spl->sp = ps[startp];
    if (endp > startp && DIST2(ps[startp], ps[startp + 3]) < slen2) {
	startp += 3;
    }
    sp[0] = ps[startp + 3];
    sp[1] = ps[startp + 2];
    sp[2] = ps[startp + 1];
    sp[3] = spl->sp;	/* ensure endpoint starts inside */

    inside_context.a.p = &sp[3];
    inside_context.a.r = &slen2;
    bezier_clip(&inside_context, inside, sp, FALSE);

    ps[startp] = sp[3];
    ps[startp + 1] = sp[2];
    ps[startp + 2] = sp[1];
    ps[startp + 3] = sp[0];
    return startp;
}

/* arrowOrthoClip:
 * For orthogonal routing, we know each Bezier of spl is a horizontal or vertical
 * line segment. We need to guarantee the B-spline stays this way. At present, we shrink
 * the arrows if necessary to fit the last segment at either end. Alternatively, we could
 * maintain the arrow size by dropping the 3 points of spl, and adding a new spl encoding
 * the arrow, something "ex_0,y_0 x_1,y_1 x_1,y_1 x_1,y_1 x_1,y_1", when the last line
 * segment is x_1,y_1 x_2,y_2 x_3,y_3 x_0,y_0. With a good deal more work, we could guarantee
 * that the truncated spl clips to the arrow shape.
 */
void arrowOrthoClip(edge_t* e, pointf* ps, int startp, int endp, bezier* spl, int sflag, int eflag)
{
    pointf p, q, r, s, t;
    double d, tlen, hlen, maxd;

    if (sflag && eflag && (endp == startp)) { /* handle special case of two arrows on a single segment */
	p = ps[endp];
	q = ps[endp+3];
	tlen = arrow_length (e, sflag);
	hlen = arrow_length (e, eflag);
        d = DIST(p, q);
	if (hlen + tlen >= d) {
	    hlen = tlen = d/3.0;
	}
	if (p.y == q.y) { /* horz segment */
	    s.y = t.y = p.y;
	    if (p.x < q.x) {
		t.x = q.x - hlen;
		s.x = p.x + tlen;
	    }
	    else {
		t.x = q.x + hlen;
		s.x = p.x - tlen;
	    }
	}
	else {            /* vert segment */
	    s.x = t.x = p.x;
	    if (p.y < q.y) {
		t.y = q.y - hlen;
		s.y = p.y + tlen;
	    }
	    else {
		t.y = q.y + hlen;
		s.y = p.y - tlen;
	    }
	}
	ps[endp] = ps[endp + 1] = s;
	ps[endp + 2] = ps[endp + 3] = t;
	spl->eflag = eflag, spl->ep = p;
	spl->sflag = sflag, spl->sp = q;
	return;
    }
    if (eflag) {
	hlen = arrow_length(e, eflag);
	p = ps[endp];
	q = ps[endp+3];
        d = DIST(p, q);
	maxd = 0.9*d;
	if (hlen >= maxd) {   /* arrow too long */
	    hlen = maxd;
	}
	if (p.y == q.y) { /* horz segment */
	    r.y = p.y;
	    if (p.x < q.x) r.x = q.x - hlen;
	    else r.x = q.x + hlen;
	}
	else {            /* vert segment */
	    r.x = p.x;
	    if (p.y < q.y) r.y = q.y - hlen;
	    else r.y = q.y + hlen;
	}
	ps[endp + 1] = p;
	ps[endp + 2] = ps[endp + 3] = r;
	spl->eflag = eflag;
	spl->ep = q;
    }
    if (sflag) {
	tlen = arrow_length(e, sflag);
	p = ps[startp];
	q = ps[startp+3];
        d = DIST(p, q);
	maxd = 0.9*d;
	if (tlen >= maxd) {   /* arrow too long */
	    tlen = maxd;
	}
	if (p.y == q.y) { /* horz segment */
	    r.y = p.y;
	    if (p.x < q.x) r.x = p.x + tlen;
	    else r.x = p.x - tlen;
	}
	else {            /* vert segment */
	    r.x = p.x;
	    if (p.y < q.y) r.y = p.y + tlen;
	    else r.y = p.y - tlen;
	}
	ps[startp] = ps[startp + 1] = r;
	ps[startp + 2] = q;
	spl->sflag = sflag;
	spl->sp = p;
    }
}

static void arrow_type_normal(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
{
    pointf q, v, a[5];
    double arrowwidth;

    arrowwidth = 0.35;
    if (penwidth > 4)
        arrowwidth *= penwidth / 4;

    v.x = -u.y * arrowwidth;
    v.y = u.x * arrowwidth;
    q.x = p.x + u.x;
    q.y = p.y + u.y;
    if (flag & ARR_MOD_INV) {
	a[0] = a[4] = p;
	a[1].x = p.x - v.x;
	a[1].y = p.y - v.y;
	a[2] = q;
	a[3].x = p.x + v.x;
	a[3].y = p.y + v.y;
    } else {
	a[0] = a[4] = q;
	a[1].x = q.x - v.x;
	a[1].y = q.y - v.y;
	a[2] = p;
	a[3].x = q.x + v.x;
	a[3].y = q.y + v.y;
    }
    if (flag & ARR_MOD_LEFT)
	gvrender_polygon(job, a, 3, !(flag & ARR_MOD_OPEN));
    else if (flag & ARR_MOD_RIGHT)
	gvrender_polygon(job, &a[2], 3, !(flag & ARR_MOD_OPEN));
    else
	gvrender_polygon(job, &a[1], 3, !(flag & ARR_MOD_OPEN));
}

static void arrow_type_crow(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
{
    pointf m, q, v, w, a[9];
    double arrowwidth, shaftwidth;

    arrowwidth = 0.45;
    if (penwidth > (4 * arrowsize) && (flag & ARR_MOD_INV))
        arrowwidth *= penwidth / (4 * arrowsize);

    shaftwidth = 0;
    if (penwidth > 1 && (flag & ARR_MOD_INV))
	shaftwidth = 0.05 * (penwidth - 1) / arrowsize;   /* arrowsize to cancel the arrowsize term already in u */

    v.x = -u.y * arrowwidth;
    v.y = u.x * arrowwidth;
    w.x = -u.y * shaftwidth;
    w.y = u.x * shaftwidth;
    q.x = p.x + u.x;
    q.y = p.y + u.y;
    m.x = p.x + u.x * 0.5;
    m.y = p.y + u.y * 0.5;
    if (flag & ARR_MOD_INV) {  /* vee */
	a[0] = a[8] = p;
	a[1].x = q.x - v.x;
	a[1].y = q.y - v.y;
	a[2].x = m.x - w.x;
	a[2].y = m.y - w.y;
	a[3].x = q.x - w.x;
	a[3].y = q.y - w.y;
	a[4] = q;
	a[5].x = q.x + w.x;
	a[5].y = q.y + w.y;
	a[6].x = m.x + w.x;
	a[6].y = m.y + w.y;
	a[7].x = q.x + v.x;
	a[7].y = q.y + v.y;
    } else {                     /* crow */
	a[0] = a[8] = q;
	a[1].x = p.x - v.x;
	a[1].y = p.y - v.y;
	a[2].x = m.x - w.x;
	a[2].y = m.y - w.y;
	a[3].x = p.x;
	a[3].y = p.y;
	a[4] = p;
	a[5].x = p.x;
	a[5].y = p.y;
	a[6].x = m.x + w.x;
	a[6].y = m.y + w.y;
	a[7].x = p.x + v.x;
	a[7].y = p.y + v.y;
    }
    if (flag & ARR_MOD_LEFT)
	gvrender_polygon(job, a, 6, 1);
    else if (flag & ARR_MOD_RIGHT)
	gvrender_polygon(job, &a[3], 6, 1);
    else
	gvrender_polygon(job, a, 9, 1);
}

static void arrow_type_gap(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
{
    pointf q, a[2];

    q.x = p.x + u.x;
    q.y = p.y + u.y;
    a[0] = p;
    a[1] = q;
    gvrender_polyline(job, a, 2);
}

static void arrow_type_tee(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
{
    pointf m, n, q, v, a[4];

    v.x = -u.y;
    v.y = u.x;
    q.x = p.x + u.x;
    q.y = p.y + u.y;
    m.x = p.x + u.x * 0.2;
    m.y = p.y + u.y * 0.2;
    n.x = p.x + u.x * 0.6;
    n.y = p.y + u.y * 0.6;
    a[0].x = m.x + v.x;
    a[0].y = m.y + v.y;
    a[1].x = m.x - v.x;
    a[1].y = m.y - v.y;
    a[2].x = n.x - v.x;
    a[2].y = n.y - v.y;
    a[3].x = n.x + v.x;
    a[3].y = n.y + v.y;
    if (flag & ARR_MOD_LEFT) {
	a[0] = m;
	a[3] = n;
    } else if (flag & ARR_MOD_RIGHT) {
	a[1] = m;
	a[2] = n;
    }
    gvrender_polygon(job, a, 4, 1);
    a[0] = p;
    a[1] = q;
    gvrender_polyline(job, a, 2);
}

static void arrow_type_box(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
{
    pointf m, q, v, a[4];

    v.x = -u.y * 0.4;
    v.y = u.x * 0.4;
    m.x = p.x + u.x * 0.8;
    m.y = p.y + u.y * 0.8;
    q.x = p.x + u.x;
    q.y = p.y + u.y;
    a[0].x = p.x + v.x;
    a[0].y = p.y + v.y;
    a[1].x = p.x - v.x;
    a[1].y = p.y - v.y;
    a[2].x = m.x - v.x;
    a[2].y = m.y - v.y;
    a[3].x = m.x + v.x;
    a[3].y = m.y + v.y;
    if (flag & ARR_MOD_LEFT) {
	a[0] = p;
	a[3] = m;
    } else if (flag & ARR_MOD_RIGHT) {
	a[1] = p;
	a[2] = m;
    }
    gvrender_polygon(job, a, 4, !(flag & ARR_MOD_OPEN));
    a[0] = m;
    a[1] = q;
    gvrender_polyline(job, a, 2);
}

static void arrow_type_diamond(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
{
    pointf q, r, v, a[5];

    v.x = -u.y / 3.;
    v.y = u.x / 3.;
    r.x = p.x + u.x / 2.;
    r.y = p.y + u.y / 2.;
    q.x = p.x + u.x;
    q.y = p.y + u.y;
    a[0] = a[4] = q;
    a[1].x = r.x + v.x;
    a[1].y = r.y + v.y;
    a[2] = p;
    a[3].x = r.x - v.x;
    a[3].y = r.y - v.y;
    if (flag & ARR_MOD_LEFT)
	gvrender_polygon(job, &a[2], 3, !(flag & ARR_MOD_OPEN));
    else if (flag & ARR_MOD_RIGHT)
	gvrender_polygon(job, a, 3, !(flag & ARR_MOD_OPEN));
    else
	gvrender_polygon(job, a, 4, !(flag & ARR_MOD_OPEN));
}

static void arrow_type_dot(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
{
    double r;
    pointf AF[2];

    r = sqrt(u.x * u.x + u.y * u.y) / 2.;
    AF[0].x = p.x + u.x / 2. - r;
    AF[0].y = p.y + u.y / 2. - r;
    AF[1].x = p.x + u.x / 2. + r;
    AF[1].y = p.y + u.y / 2. + r;
    gvrender_ellipse(job, AF, 2, !(flag & ARR_MOD_OPEN));
}


/* Draw a concave semicircle using a single cubic bezier curve that touches p at its midpoint.
 * See http://digerati-illuminatus.blogspot.com.au/2008/05/approximating-semicircle-with-cubic.html for details.
 */
static void arrow_type_curve(GVJ_t* job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
{
    double arrowwidth = penwidth > 4 ? 0.5 * penwidth / 4 : 0.5;
    pointf q, v, w;
    pointf AF[4], a[2];

    q.x = p.x + u.x;
    q.y = p.y + u.y; 
    v.x = -u.y * arrowwidth; 
    v.y = u.x * arrowwidth;
    w.x = v.y; // same direction as u, same magnitude as v.
    w.y = -v.x;
    a[0] = p;
    a[1] = q;

    AF[0].x = p.x + v.x + w.x;
    AF[0].y = p.y + v.y + w.y;

    AF[3].x = p.x - v.x + w.x;
    AF[3].y = p.y - v.y + w.y;

    if (flag & ARR_MOD_INV) {  /* ----(-| */
        AF[1].x = p.x + 0.95 * v.x + w.x + w.x * 4.0 / 3.0;
        AF[1].y = AF[0].y + w.y * 4.0 / 3.0;

        AF[2].x = p.x - 0.95 * v.x + w.x + w.x * 4.0 / 3.0;
        AF[2].y = AF[3].y + w.y * 4.0 / 3.0;
    }
    else {  /* ----)-| */
        AF[1].x = p.x + 0.95 * v.x + w.x - w.x * 4.0 / 3.0;
        AF[1].y = AF[0].y - w.y * 4.0 / 3.0;

        AF[2].x = p.x - 0.95 * v.x + w.x - w.x * 4.0 / 3.0;
        AF[2].y = AF[3].y - w.y * 4.0 / 3.0;
    }

    gvrender_polyline(job, a, 2);
    if (flag & ARR_MOD_LEFT)
	Bezier(AF, 3, 0.5, NULL, AF);
    else if (flag & ARR_MOD_RIGHT)
	Bezier(AF, 3, 0.5, AF, NULL);
    gvrender_beziercurve(job, AF, sizeof(AF) / sizeof(pointf), FALSE, FALSE, FALSE);
}


static pointf arrow_gen_type(GVJ_t * job, pointf p, pointf u, double arrowsize, double penwidth, int flag)
{
    int f;
    arrowtype_t *arrowtype;

    f = flag & ((1 << BITS_PER_ARROW_TYPE) - 1);
    for (arrowtype = Arrowtypes; arrowtype->type; arrowtype++) {
	if (f == arrowtype->type) {
	    u.x *= arrowtype->lenfact * arrowsize;
	    u.y *= arrowtype->lenfact * arrowsize;
	    (arrowtype->gen) (job, p, u, arrowsize, penwidth, flag);
	    p.x = p.x + u.x;
	    p.y = p.y + u.y;
	    break;
	}
    }
    return p;
}

boxf arrow_bb(pointf p, pointf u, double arrowsize, int flag)
{
    double s;
    boxf bb;
    double ax,ay,bx,by,cx,cy,dx,dy;
    double ux2, uy2;

    /* generate arrowhead vector */
    u.x -= p.x;
    u.y -= p.y;
    /* the EPSILONs are to keep this stable as length of u approaches 0.0 */
    s = ARROW_LENGTH * arrowsize / (sqrt(u.x * u.x + u.y * u.y) + EPSILON);
    u.x += (u.x >= 0.0) ? EPSILON : -EPSILON;
    u.y += (u.y >= 0.0) ? EPSILON : -EPSILON;
    u.x *= s;
    u.y *= s;

    /* compute all 4 corners of rotated arrowhead bounding box */
    ux2 = u.x / 2.;
    uy2 = u.y / 2.;
    ax = p.x - uy2;
    ay = p.y - ux2;
    bx = p.x + uy2;
    by = p.y + ux2;
    cx = ax + u.x;
    cy = ay + u.y;
    dx = bx + u.x;
    dy = by + u.y;

    /* compute a right bb */
    bb.UR.x = MAX(ax, MAX(bx, MAX(cx, dx)));
    bb.UR.y = MAX(ay, MAX(by, MAX(cy, dy)));
    bb.LL.x = MIN(ax, MIN(bx, MIN(cx, dx)));
    bb.LL.y = MIN(ay, MIN(by, MIN(cy, dy)));
 
    return bb;
}

void arrow_gen(GVJ_t * job, emit_state_t emit_state, pointf p, pointf u, double arrowsize, double penwidth, int flag)
{
    obj_state_t *obj = job->obj;
    double s;
    int i, f;
    emit_state_t old_emit_state;

    old_emit_state = obj->emit_state;
    obj->emit_state = emit_state;

    /* Dotted and dashed styles on the arrowhead are ugly (dds) */
    /* linewidth needs to be reset */
    gvrender_set_style(job, job->gvc->defaultlinestyle);

    gvrender_set_penwidth(job, penwidth);

    /* generate arrowhead vector */
    u.x -= p.x;
    u.y -= p.y;
    /* the EPSILONs are to keep this stable as length of u approaches 0.0 */
    s = ARROW_LENGTH / (sqrt(u.x * u.x + u.y * u.y) + EPSILON);
    u.x += (u.x >= 0.0) ? EPSILON : -EPSILON;
    u.y += (u.y >= 0.0) ? EPSILON : -EPSILON;
    u.x *= s;
    u.y *= s;

    /* the first arrow head - closest to node */
    for (i = 0; i < NUMB_OF_ARROW_HEADS; i++) {
        f = (flag >> (i * BITS_PER_ARROW)) & ((1 << BITS_PER_ARROW) - 1);
	if (f == ARR_TYPE_NONE)
	    break;
        p = arrow_gen_type(job, p, u, arrowsize, penwidth, f);
    }

    obj->emit_state = old_emit_state;
}
