multispline.c

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/*************************************************************************
 * 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
 * https://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors: Details at https://graphviz.org
 *************************************************************************/
 
#include <assert.h>
#include <cgraph/alloc.h>
#include <float.h>
#include <limits.h>
#include <neatogen/multispline.h>
#include <neatogen/delaunay.h>
#include <neatogen/neatoprocs.h>
#include <math.h>
#include <stdbool.h>
#include <stddef.h>
 
static bool spline_merge(node_t * n)
{
    (void)n;
    return false;
}
 
static bool swap_ends_p(edge_t * e)
{
    (void)e;
    return false;
}
 
static splineInfo sinfo = {.swapEnds = swap_ends_p,
                           .splineMerge = spline_merge};
 
typedef struct {
    int i, j;
} ipair;
 
typedef struct _tri {
    ipair v;
    struct _tri *nxttri;
} tri;
 
typedef struct {
    Ppoly_t poly;       /* base polygon used for routing an edge */
    tri **triMap;       /* triMap[j] is list of all opposite sides of 
                           triangles containing vertex j, represented
                           as the indices of the two points in poly */
} tripoly_t;
 
/*
 * Support for map from I x I -> I
 */
typedef struct {
    Dtlink_t link;              /* cdt data */
    int a[2];                   /* key */
    int t;
} item;
 
static int cmpItem(void *item1, void *item2) {
    const int *p1 = item1;
    const int *p2 = item2;
    if (p1[0] < p2[0]) return -1;
    if (p1[0] > p2[0]) return 1;
    if (p1[1] < p2[1]) return -1;
    if (p1[1] > p2[1]) return 1;
    return 0;
}
 
/* newItem:
 */
static void *newItem(item *objp, Dtdisc_t *disc) {
    item *newp = gv_alloc(sizeof(item));
 
    (void)disc;
    newp->a[0] = objp->a[0];
    newp->a[1] = objp->a[1];
    newp->t = objp->t;
 
    return newp;
}
 
static Dtdisc_t itemdisc = {
    .key = offsetof(item, a),
    .size = 2 * sizeof(int),
    .link = offsetof(item, link),
    .makef = (Dtmake_f)newItem,
    .freef = free,
    .comparf = cmpItem,
};
 
static void addMap(Dt_t * map, int a, int b, int t)
{
    item it;
    int tmp;
    if (a > b) {
        tmp = a;
        a = b;
        b = tmp;
    }
    it.a[0] = a;
    it.a[1] = b;
    it.t = t;
    dtinsert(map, &it);
}
 
/* mapSegToTri:
 * Create mapping from indices of side endpoints to triangle id 
 * We use a set rather than a bag because the segments used for lookup
 * will always be a side of a polygon and hence have a unique triangle.
 */
static Dt_t *mapSegToTri(surface_t * sf)
{
    Dt_t *map = dtopen(&itemdisc, Dtoset);
    int i, a, b, c;
    int *ps = sf->faces;
    for (i = 0; i < sf->nfaces; i++) {
        a = *ps++;
        b = *ps++;
        c = *ps++;
        addMap(map, a, b, i);
        addMap(map, b, c, i);
        addMap(map, c, a, i);
    }
    return map;
}
 
static int findMap(Dt_t * map, int a, int b)
{
    item it;
    item *ip;
    if (a > b) {
        int tmp = a;
        a = b;
        b = tmp;
    }
    it.a[0] = a;
    it.a[1] = b;
    ip = dtsearch(map, &it);
    assert(ip);
    return ip->t;
}
 
/*
 * Support for map from I -> I
 */
 
typedef struct {
    Dtlink_t link;              /* cdt data */
    int i;                      /* key */
    int j;
} Ipair;
 
static int cmpIpair(void *pair1, void *pair2) {
    const int *p1 = pair1;
    const int *p2 = pair2;
    if (*p1 < *p2) {
        return -1;
    }
    if (*p1 > *p2) {
        return 1;
    }
    return 0;
}
 
static void *newIpair(Ipair *objp, Dtdisc_t *disc) {
    Ipair *newp = gv_alloc(sizeof(Ipair));
 
    (void)disc;
    newp->i = objp->i;
    newp->j = objp->j;
 
    return newp;
}
 
static Dtdisc_t ipairdisc = {
    .key = offsetof(Ipair, i),
    .size = sizeof(int),
    .link = offsetof(Ipair, link),
    .makef = (Dtmake_f)newIpair,
    .freef = free,
    .comparf = cmpIpair,
};
 
static void vmapAdd(Dt_t * map, int i, int j)
{
    Ipair obj;
    obj.i = i;
    obj.j = j;
    dtinsert(map, &obj);
}
 
static int vMap(Dt_t * map, int i)
{
    Ipair *ip;
    ip = dtmatch(map, &i);
    return ip->j;
}
 
/* mapTri:
 * Map vertex indices from router_t to tripoly_t coordinates.
 */
static void mapTri(Dt_t * map, tri * tp)
{
    for (; tp; tp = tp->nxttri) {
        tp->v.i = vMap(map, tp->v.i);
        tp->v.j = vMap(map, tp->v.j);
    }
}
 
/* addTri:
 */
static tri *
addTri(int i, int j, tri * oldp)
{
    tri *tp = gv_alloc(sizeof(tri));
    tp->v.i = i;
    tp->v.j = j;
    tp->nxttri = oldp;
    return tp;
}
 
/* bisect:
 * Return the angle bisecting the angle pp--cp--np
 */
static double bisect(pointf pp, pointf cp, pointf np)
{
    double theta, phi;
    theta = atan2(np.y - cp.y, np.x - cp.x);
    phi = atan2(pp.y - cp.y, pp.x - cp.x);
    return (theta + phi) / 2.0;
}
 
/* raySeg:
 * Check if ray v->w intersects segment a--b.
 */
static int raySeg(pointf v, pointf w, pointf a, pointf b)
{
    int wa = wind(v, w, a);
    int wb = wind(v, w, b);
    if (wa == wb)
        return 0;
    if (wa == 0) {
        return wind(v, b, w) * wind(v, b, a) >= 0;
    } else {
        return wind(v, a, w) * wind(v, a, b) >= 0;
    }
}
 
/* raySegIntersect:
 * Find the point p where ray v->w intersects segment ai-bi, if any.
 * Return 1 on success, 0 on failure
 */
static int
raySegIntersect(pointf v, pointf w, pointf a, pointf b, pointf * p)
{
    if (raySeg(v, w, a, b))
        return line_intersect(v, w, a, b, p);
    else
        return 0;
}
 
/* triPoint:
 * Given the triangle vertex v, and point w so that v->w points
 * into the polygon, return where the ray v->w intersects the
 * polygon. The search uses all of the opposite sides of triangles
 * with v as vertex.
 * Return 0 on success; 1 on failure.
 */
static int
triPoint(tripoly_t * trip, int vx, pointf v, pointf w, pointf * ip)
{
    tri *tp;
 
    for (tp = trip->triMap[vx]; tp; tp = tp->nxttri) {
        if (raySegIntersect
            (v, w, trip->poly.ps[tp->v.i], trip->poly.ps[tp->v.j], ip))
            return 0;
    }
    return 1;
}
 
/* ctrlPtIdx:
 * Find the index of v in the points polys->ps.
 * We start at 1 since the point corresponding to 0 
 * will never be used as v.
 */
static int ctrlPtIdx(pointf v, Ppoly_t * polys)
{
    pointf w;
    for (size_t i = 1; i < polys->pn; i++) {
        w = polys->ps[i];
        if (w.x == v.x && w.y == v.y) {
            assert(i <= INT_MAX);
            return (int)i;
        }
    }
    return -1;
}
 
#define SEP 15
 
/* mkCtrlPts:
 * Generate mult points associated with v.
 * The points will lie on the ray bisecting the angle prev--v--nxt.
 * The first point will aways be v.
 * The rest are positioned equally spaced with maximum spacing SEP.
 * In addition, they all lie within the polygon trip->poly.
 * Parameter s gives the index after which a vertex lies on the
 * opposite side. This is necessary to get the "curvature" of the
 * path correct.
 */
static pointf *mkCtrlPts(int s, int mult, pointf prev, pointf v,
                           pointf nxt, tripoly_t * trip)
{
    int idx = ctrlPtIdx(v, &trip->poly);
    int i;
    double d, sep, theta, sinTheta, cosTheta;
    pointf q, w;
 
    if (idx < 0)
        return NULL;
 
    pointf *ps = gv_calloc(mult, sizeof(pointf));
    theta = bisect(prev, v, nxt);
    sinTheta = sin(theta);
    cosTheta = cos(theta);
    w.x = v.x + 100 * cosTheta;
    w.y = v.y + 100 * sinTheta;
    if (idx > s) {
        if (wind(prev, v, w) != 1) {
            sinTheta *= -1;
            cosTheta *= -1;
            w.x = v.x + 100 * cosTheta;
            w.y = v.y + 100 * sinTheta;
        }
    } else if (wind(prev, v, w) != -1) {
        sinTheta *= -1;
        cosTheta *= -1;
        w.x = v.x + 100 * cosTheta;
        w.y = v.y + 100 * sinTheta;
    }
 
    if (triPoint(trip, idx, v, w, &q)) {
        return 0;
    }
 
    d = DIST(q, v);
    if (d >= mult * SEP)
        sep = SEP;
    else
        sep = d / mult;
    if (idx < s) {
        for (i = 0; i < mult; i++) {
            ps[i].x = v.x + i * sep * cosTheta;
            ps[i].y = v.y + i * sep * sinTheta;
        }
    } else {
        for (i = 0; i < mult; i++) {
            ps[mult - i - 1].x = v.x + i * sep * cosTheta;
            ps[mult - i - 1].y = v.y + i * sep * sinTheta;
        }
    }
    return ps;
}
 
/*
 * Simple graph structure for recording the triangle graph.
 */
 
typedef struct {
    size_t ne;      // no. of edges.
    int *edges;     /* indices of edges adjacent to node. */
    pointf ctr;     /* center of triangle. */
} tnode;
 
typedef struct {
    int t, h;       /* indices of head and tail nodes */
    ipair seg;      /* indices of points forming shared segment */
    double dist;    /* length of edge; usually distance between centers */
} tedge;
 
typedef struct {
    tnode *nodes;
    size_t nnodes; // number of nodes
    tedge *edges;
    int nedges; // number of edges
} tgraph;
 
struct router_s {
    int pn;     /* no. of points */
    pointf *ps; /* all points in configuration */
    int *obs;   /* indices in obstacle i are obs[i]...obs[i+1]-1 */
    int *tris;  /* indices of triangle i are tris[3*i]...tris[3*i+2] */
    Dt_t *trimap; /* map from obstacle side (a,b) to index of adj. triangle */
    int tn;       /* no. of nodes in tg */
    tgraph *tg;   /* graph of triangles */
};
 
/* triCenter:
 * Given an array of points and 3 integer indices,
 * compute and return the center of the triangle.
 */
static pointf triCenter(pointf * pts, int *idxs)
{
    pointf a = pts[*idxs++];
    pointf b = pts[*idxs++];
    pointf c = pts[*idxs++];
    pointf p;
    p.x = (a.x + b.x + c.x) / 3.0;
    p.y = (a.y + b.y + c.y) / 3.0;
    return p;
}
 
#define MARGIN 32
 
/* bbox:
 * Compute bounding box of polygons, and return it
 * with an added margin of MARGIN.
 * Store total number of points in *np.
 */
static boxf bbox(Ppoly_t** obsp, int npoly, int *np)
{
    boxf bb;
    int i, cnt = 0;
    pointf p;
    Ppoly_t* obs;
 
    bb.LL.x = bb.LL.y = DBL_MAX;
    bb.UR.x = bb.UR.y = -DBL_MAX;
 
    for (i = 0; i < npoly; i++) {
        obs = *obsp++;
        for (size_t j = 0; j < obs->pn; j++) {
            p = obs->ps[j];
            bb.LL.x = fmin(bb.LL.x, p.x);
            bb.UR.x = fmax(bb.UR.x, p.x);
            bb.LL.y = fmin(bb.LL.y, p.y);
            bb.UR.y = fmax(bb.UR.y, p.y);
            cnt++;
        }
    }
 
    *np = cnt;
 
    bb.LL.x -= MARGIN;
    bb.LL.y -= MARGIN;
    bb.UR.x += MARGIN;
    bb.UR.y += MARGIN;
 
    return bb;
}
 
static int *mkTriIndices(surface_t * sf)
{
    int *tris = gv_calloc(3 * sf->nfaces, sizeof(int));
    memcpy(tris, sf->faces, 3 * sf->nfaces * sizeof(int));
    return tris;
}
 
/* sharedEdge:
 * Returns a pair of integer (x,y), x < y, where x and y are the
 * indices of the two vertices of the shared edge.
 */
static ipair sharedEdge(int *p, int *q)
{
    ipair pt;
    int tmp, p1, p2;
    p1 = *p;
    p2 = *(p + 1);
    if (p1 == *q) {
        if (p2 != *(q + 1) && p2 != *(q + 2)) {
            p2 = *(p + 2);
        }
    } else if (p1 == *(q + 1)) {
        if (p2 != *q && p2 != *(q + 2)) {
            p2 = *(p + 2);
        }
    } else if (p1 == *(q + 2)) {
        if (p2 != *q && p2 != *(q + 1)) {
            p2 = *(p + 2);
        }
    } else {
        p1 = *(p + 2);
    }
 
    if (p1 > p2) {
        tmp = p1;
        p1 = p2;
        p2 = tmp;
    }
    pt.i = p1;
    pt.j = p2;
    return pt;
}
 
/* addTriEdge:
 * Add an edge to g, with tail t, head h, and shared
 * segment seg.
 */
static void addTriEdge(tgraph *g, int t, int h, ipair seg) {
    g->edges = gv_recalloc(g->edges, g->nedges, g->nedges + 1,
                           sizeof(g->edges[0]));
    tedge *ep = g->edges + g->nedges;
    tnode *tp = g->nodes + t;
    tnode *hp = g->nodes + h;
 
    ep->t = t;
    ep->h = h;
    ep->dist = DIST(tp->ctr, hp->ctr);
    ep->seg = seg;
 
    tp->edges = gv_recalloc(tp->edges, tp->ne, tp->ne + 1,
                            sizeof(tp->edges[0]));
    tp->edges[tp->ne++] = g->nedges;
    hp->edges = gv_recalloc(hp->edges, hp->ne, hp->ne + 1,
                            sizeof(hp->edges[0]));
    hp->edges[hp->ne++] = g->nedges;
 
    g->nedges++;
}
 
static void freeTriGraph(tgraph * tg)
{
    for (size_t i = 0; i < tg->nnodes; ++i) {
        free(tg->nodes[i].edges);
    }
    free(tg->nodes);
    free(tg->edges);
    free(tg);
}
 
/* mkTriGraph:
 * Generate graph with triangles as nodes and an edge iff two triangles
 * share an edge.
 */
static tgraph *mkTriGraph(surface_t *sf, pointf *pts) {
    tnode *np;
    int j, i, ne = 0;
    int *jp;
 
    /* ne is twice no. of edges */
    for (i = 0; i < 3 * sf->nfaces; i++)
        if (sf->neigh[i] != -1)
            ne++;
 
    tgraph *g = gv_alloc(sizeof(tgraph));
 
    /* plus 2 for nodes added as endpoints of an edge */
    g->nnodes = sf->nfaces + 2;
    g->nodes = gv_calloc(g->nnodes, sizeof(tnode));
 
    for (i = 0; i < sf->nfaces; i++) {
        np = g->nodes + i;
        np->ctr = triCenter(pts, sf->faces + 3 * i);
    }
 
    for (i = 0; i < sf->nfaces; i++) {
        np = g->nodes + i;
        jp = sf->neigh + 3 * i;
        ne = 0;
        while (ne < 3 && (j = *jp++) != -1) {
            if (i < j) {
                ipair seg =
                    sharedEdge(sf->faces + 3 * i, sf->faces + 3 * j);
                addTriEdge(g, i, j, seg);
            }
            ne++;
        }
    }
 
    return g;
}
 
void freeRouter(router_t * rtr)
{
    free(rtr->ps);
    free(rtr->obs);
    free(rtr->tris);
    dtclose(rtr->trimap);
    freeTriGraph(rtr->tg);
    free(rtr);
}
 
router_t *mkRouter(Ppoly_t** obsp, int npoly)
{
    router_t *rtr = gv_alloc(sizeof(router_t));
    Ppoly_t* obs;
    boxf bb;
    int npts;
    surface_t *sf;
    /* points in obstacle i have indices obsi[i] through obsi[i+1]-1 in pts
     */
    int *obsi = gv_calloc(npoly + 1, sizeof(int));
    int i, ix = 4, six = 0;
 
    bb = bbox(obsp, npoly, &npts);
    npts += 4;                  /* 4 points of bounding box */
    pointf *pts = gv_calloc(npts, sizeof(pointf)); // all points are stored in pts
    int *segs = gv_calloc(2 * npts, sizeof(int)); // indices of points forming segments
 
    /* store bounding box in CCW order */
    pts[0] = bb.LL;
    pts[1].x = bb.UR.x;
    pts[1].y = bb.LL.y;
    pts[2] = bb.UR;
    pts[3].x = bb.LL.x;
    pts[3].y = bb.UR.y;
    for (i = 1; i <= 4; i++) {
        segs[six++] = i - 1;
        if (i < 4)
            segs[six++] = i;
        else
            segs[six++] = 0;
    }
 
    /* store obstacles in CW order and generate constraint segments */
    for (i = 0; i < npoly; i++) {
        obsi[i] = ix;
        obs = *obsp++;
        for (size_t j = 1; j <= obs->pn; j++) {
            segs[six++] = ix;
            if (j < obs->pn)
                segs[six++] = ix + 1;
            else
                segs[six++] = obsi[i];
            pts[ix++] = obs->ps[j - 1];
        }
    }
    obsi[i] = ix;
 
    /* copy points into coordinate arrays */
    double *x = gv_calloc(npts, sizeof(double));
    double *y = gv_calloc(npts, sizeof(double));
    for (i = 0; i < npts; i++) {
        x[i] = pts[i].x;
        y[i] = pts[i].y;
    }
    sf = mkSurface(x, y, npts, segs, npts);
    free(x);
    free(y);
    free(segs);
 
    rtr->ps = pts;
    rtr->pn = npts;
    rtr->obs = obsi;
    rtr->tris = mkTriIndices(sf);
    rtr->trimap = mapSegToTri(sf);
    rtr->tn = sf->nfaces;
    rtr->tg = mkTriGraph(sf, pts);
 
    freeSurface(sf);
    return rtr;
}
 
/* finishEdge:
 * Finish edge generation, clipping to nodes and adding arrowhead
 * if necessary, and adding edge labels
 */
static void finishEdge(edge_t* e, Ppoly_t spl, int flip) {
    if (flip) {
        for (size_t j = 0; j < spl.pn / 2; j++) {
            pointf tmp = spl.ps[spl.pn - 1 - j];
            spl.ps[spl.pn - 1 - j] = spl.ps[j];
            spl.ps[j] = tmp;
        }
    }
    if (Verbose > 1)
        fprintf(stderr, "spline %s %s\n", agnameof(agtail(e)), agnameof(aghead(e)));
    clip_and_install(e, aghead(e), spl.ps, spl.pn, &sinfo);
 
    addEdgeLabels(e);
}
 
#define EQPT(p,q) (((p).x==(q).x)&&((p).y==(q).y))
 
/* tweakEnd:
 * Hack because path routing doesn't know about the interiors
 * of polygons. If the first or last segment of the shortest path
 * lies along one of the polygon boundaries, the path may flip
 * inside the polygon. To avoid this, we shift the point a bit.
 *
 * If the edge p(=poly.ps[s])-q of the shortest path is also an
 * edge of the border polygon, move p slightly inside the polygon
 * and return it. If prv and nxt are the two vertices adjacent to
 * p in the polygon, let m be the midpoint of prv--nxt. We then
 * move a tiny bit along the ray p->m.
 *
 * Otherwise, return p unchanged.
 */
static Ppoint_t tweakEnd(Ppoly_t poly, size_t s, Ppoint_t q) {
    Ppoint_t prv, nxt, p;
 
    p = poly.ps[s];
    nxt = poly.ps[(s + 1) % poly.pn];
    if (s == 0)
        prv = poly.ps[poly.pn-1];
    else
        prv = poly.ps[s - 1];
    if (EQPT(q, nxt) || EQPT(q, prv) ){
        Ppoint_t m;
        m.x = (nxt.x + prv.x)/2.0 - p.x;
        m.y = (nxt.y + prv.y)/2.0 - p.y;
        const double d = hypot(m.x, m.y);
        p.x += 0.1*m.x/d;
        p.y += 0.1*m.y/d;
    }
    return p;
}
 
static void tweakPath(Ppoly_t poly, size_t t, Ppolyline_t pl) {
    pl.ps[0] = tweakEnd(poly, 0, pl.ps[1]);
    pl.ps[pl.pn-1] = tweakEnd (poly, t, pl.ps[pl.pn-2]);
}
 
 
/* genroute:
 * Generate splines for e and cohorts.
 * Edges go from 0 to t.
 * Return 0 on success.
 */
static int genroute(tripoly_t *trip, int t, edge_t *e, int doPolyline) {
    pointf eps[2];
    Pvector_t evs[2];
    pointf **cpts = NULL;               /* lists of control points */
    Ppoly_t poly;
    Ppolyline_t pl, spl;
    Ppolyline_t mmpl;
    Pedge_t *medges = NULL;
    int mult = ED_count(e);
    node_t* head = aghead(e);
    int rv = 0;
 
    poly.ps = NULL;
    pl.pn = 0;
    eps[0].x = trip->poly.ps[0].x, eps[0].y = trip->poly.ps[0].y;
    eps[1].x = trip->poly.ps[t].x, eps[1].y = trip->poly.ps[t].y;
    if (Pshortestpath(&(trip->poly), eps, &pl) < 0) {
        agwarningf("Could not create control points for multiple spline for edge (%s,%s)\n", agnameof(agtail(e)), agnameof(aghead(e)));
        rv = 1;
        goto finish;
    }
 
    if (pl.pn == 2) {
        makeStraightEdge(agraphof(head), e, doPolyline, &sinfo);
        goto finish;
    }
 
    evs[0].x = evs[0].y = 0;
    evs[1].x = evs[1].y = 0;
 
    if (mult == 1 || Concentrate) {
        poly = trip->poly;
        medges = gv_calloc(poly.pn, sizeof(Pedge_t));
        for (size_t j = 0; j < poly.pn; j++) {
            medges[j].a = poly.ps[j];
            medges[j].b = poly.ps[(j + 1) % poly.pn];
        }
        assert(t >= 0);
        tweakPath(poly, (size_t)t, pl);
        if (Proutespline(medges, poly.pn, pl, evs, &spl) < 0) {
            agwarningf("Could not create control points for multiple spline for edge (%s,%s)\n", agnameof(agtail(e)), agnameof(aghead(e)));
            rv = 1;
            goto finish;
        }
        finishEdge(e, spl, aghead(e) != head);
        free(medges);
 
        return 0;
    }
    
    const size_t pn = 2 * (pl.pn - 1);
 
    cpts = gv_calloc(pl.pn - 2, sizeof(pointf *));
    for (size_t i = 0; i + 2 < pl.pn; i++) {
        cpts[i] =
            mkCtrlPts(t, mult+1, pl.ps[i], pl.ps[i + 1], pl.ps[i + 2], trip);
        if (!cpts[i]) {
            agwarningf("Could not create control points for multiple spline for edge (%s,%s)\n", agnameof(agtail(e)), agnameof(aghead(e)));
            rv = 1;
            goto finish;
        }
    }
 
    poly.ps = gv_calloc(pn, sizeof(pointf));
    poly.pn = pn;
 
    for (int i = 0; i < mult; i++) {
        poly.ps[0] = eps[0];
        for (size_t j = 1; j + 1 < pl.pn; j++) {
            poly.ps[j] = cpts[j - 1][i];
        }
        poly.ps[pl.pn - 1] = eps[1];
        for (size_t j = 1; j + 1 < pl.pn; j++) {
            poly.ps[pn - j] = cpts[j - 1][i + 1];
        }
        if (Pshortestpath(&poly, eps, &mmpl) < 0) {
            agwarningf("Could not create control points for multiple spline for edge (%s,%s)\n", agnameof(agtail(e)), agnameof(aghead(e)));
            rv = 1;
            goto finish;
        }
 
        if (doPolyline) {
            make_polyline (mmpl, &spl);
        }
        else {
            medges = gv_calloc(poly.pn, sizeof(Pedge_t));
            for (size_t j = 0; j < poly.pn; j++) {
                medges[j].a = poly.ps[j];
                medges[j].b = poly.ps[(j + 1) % poly.pn];
            }
            tweakPath(poly, pl.pn - 1, mmpl);
            if (Proutespline(medges, poly.pn, mmpl, evs, &spl) < 0) {
                agwarningf("Could not create control points for multiple spline for edge (%s,%s)\n", 
                    agnameof(agtail(e)), agnameof(aghead(e)));
                rv = 1;
                goto finish;
            }
        }
        finishEdge(e, spl, aghead(e) != head);
 
        e = ED_to_virt(e);
    }
 
finish :
    if (cpts) {
        for (size_t i = 0; i + 2 < pl.pn; i++)
            free(cpts[i]);
        free(cpts);
    }
    free(medges);
    free(poly.ps);
    return rv;
}
 
#define NSMALL -0.0000000001
 
/* inCone:
 * Returns true iff q is in the convex cone a-b-c
 */
static int
inCone (pointf a, pointf b, pointf c, pointf q)
{
  return area2(q,a,b) >= NSMALL && area2(q,b,c) >= NSMALL;
}
 
static pointf north = {0, 1};
static pointf northeast = {1, 1};
static pointf east = {1, 0};
static pointf southeast = {1, -1};
static pointf south = {0, -1};
static pointf southwest = {-1, -1};
static pointf west = {-1, 0};
static pointf northwest = {-1, 1};
 
/* addEndpoint:
 * Add node to graph representing spline end point p inside obstruction obs_id.
 * For each side of obstruction, add edge from p to corresponding triangle.
 * The node id of the new node in the graph is v_id.
 * If p lies on the side of its node (sides != 0), we limit the triangles
 * to those within 45 degrees of each side of the natural direction of p.
 */
static void addEndpoint(router_t * rtr, pointf p, node_t* v, int v_id, int sides)
{
    int obs_id = ND_lim(v);
    int starti = rtr->obs[obs_id];
    int endi = rtr->obs[obs_id + 1];
    pointf* pts = rtr->ps;
    int i, t;
    pointf vr, v0, v1;
 
    switch (sides) {
    case TOP :
        vr = add_pointf (p, north);
        v0 = add_pointf (p, northwest);
        v1 = add_pointf (p, northeast);
        break;
    case TOP|RIGHT :
        vr = add_pointf (p, northeast);
        v0 = add_pointf (p, north);
        v1 = add_pointf (p, east);
        break;
    case RIGHT :
        vr = add_pointf (p, east);
        v0 = add_pointf (p, northeast);
        v1 = add_pointf (p, southeast);
        break;
    case BOTTOM|RIGHT :
        vr = add_pointf (p, southeast);
        v0 = add_pointf (p, east);
        v1 = add_pointf (p, south);
        break;
    case BOTTOM :
        vr = add_pointf (p, south);
        v0 = add_pointf (p, southeast);
        v1 = add_pointf (p, southwest);
        break;
    case BOTTOM|LEFT :
        vr = add_pointf (p, southwest);
        v0 = add_pointf (p, south);
        v1 = add_pointf (p, west);
        break;
    case LEFT :
        vr = add_pointf (p, west);
        v0 = add_pointf (p, southwest);
        v1 = add_pointf (p, northwest);
        break;
    case TOP|LEFT :
        vr = add_pointf (p, northwest);
        v0 = add_pointf (p, west);
        v1 = add_pointf (p, north);
        break;
    case 0 :
        break;
    default :
        assert (0);
        break;
    }
 
    rtr->tg->nodes[v_id].ne = 0;
    rtr->tg->nodes[v_id].ctr = p;
    for (i = starti; i < endi; i++) {
        ipair seg;
        seg.i = i;
        if (i < endi - 1)
            seg.j = i + 1;
        else
            seg.j = starti;
        t = findMap(rtr->trimap, seg.i, seg.j);
        if (sides && !inCone (v0, p, v1, pts[seg.i]) && !inCone (v0, p, v1, pts[seg.j]) && !raySeg(p,vr,pts[seg.i],pts[seg.j]))
            continue;
        addTriEdge(rtr->tg, v_id, t, seg);
    }
    assert(rtr->tg->nodes[v_id].ne > 0 && "no edges were added");
}
 
/* edgeToSeg:
 * Given edge from i to j, find segment associated
 * with the edge.
 *
 * This lookup could be made faster by modifying the 
 * shortest path algorithm to store the edges rather than
 * the nodes.
 */
static ipair edgeToSeg(tgraph * tg, int i, int j)
{
    ipair ip = {0, 0};
    tnode *np = tg->nodes + i;
    tedge *ep;
 
    for (size_t k = 0; k < np->ne; k++) {
        ep = tg->edges + np->edges[k];
        if (ep->t == j || ep->h == j)
            return ep->seg;
    }
 
    assert(0);
    return ip;
}
 
static void
freeTripoly (tripoly_t* trip)
{
    tri* tp;
    tri* nxt;
 
    free (trip->poly.ps);
    for (size_t i = 0; i < trip->poly.pn; i++) {
        for (tp = trip->triMap[i]; tp; tp = nxt) {
            nxt = tp->nxttri;
            free (tp);
        }
    }
    free (trip->triMap);
    free (trip);
}
 
/* Auxiliary data structure used to translate a path of rectangles
 * into a polygon. Each side_t represents a vertex on one side of
 * the polygon. v is the index of the vertex in the global router_t,
 * and ts is a linked list of the indices of segments of sides opposite
 * to v in some triangle on the path. These lists will be translated
 * to polygon indices by mapTri, and stored in tripoly_t.triMap.
 */
typedef struct {
    int v;
    tri *ts;
} side_t;
 
/* mkPoly:
 * Construct simple polygon from shortest path from t to s in g.
 * dad gives the indices of the triangles on path.
 * sx used to store index of s in points.
 * index of t is always 0
 */
static tripoly_t *mkPoly(router_t * rtr, int *dad, int s, int t,
                         pointf p_s, pointf p_t, int *sx)
{
    tripoly_t *ps;
    int nxt;
    ipair p;
    size_t nt = 0;
    int idx;
    int cnt1 = 0;
    int cnt2 = 0;
    pointf *pts;
    /* maps vertex index used in router_t to vertex index used in tripoly */
    Dt_t *vmap;
 
    /* count number of triangles in path */
    for (nxt = dad[t]; nxt != s; nxt = dad[nxt]) {
        nt++;
        assert (nxt != dad[nxt] && "infinite loop due to 'nxt' not changing");
    }
 
    side_t *side1 = gv_calloc(nt + 4, sizeof(side_t));
    side_t *side2 = gv_calloc(nt + 4, sizeof(side_t));
 
    nxt = dad[t];
    p = edgeToSeg(rtr->tg, nxt, t);
    side1[cnt1].ts = addTri(-1, p.j, NULL);
    side1[cnt1++].v = p.i;
    side2[cnt2].ts = addTri(-1, p.i, NULL);
    side2[cnt2++].v = p.j;
 
    t = nxt;
    for (nxt = dad[t]; nxt >= 0; nxt = dad[nxt]) {
        p = edgeToSeg(rtr->tg, t, nxt);
        if (p.i == side1[cnt1 - 1].v) {
            side1[cnt1 - 1].ts =
                addTri(side2[cnt2 - 1].v, p.j, side1[cnt1 - 1].ts);
            side2[cnt2 - 1].ts =
                addTri(side1[cnt1 - 1].v, p.j, side2[cnt2 - 1].ts);
            side2[cnt2].ts =
                addTri(side2[cnt2 - 1].v, side1[cnt1 - 1].v, NULL);
            side2[cnt2++].v = p.j;
        } else if (p.i == side2[cnt2 - 1].v) {
            side1[cnt1 - 1].ts =
                addTri(side2[cnt2 - 1].v, p.j, side1[cnt1 - 1].ts);
            side2[cnt2 - 1].ts =
                addTri(side1[cnt1 - 1].v, p.j, side2[cnt2 - 1].ts);
            side1[cnt1].ts =
                addTri(side2[cnt2 - 1].v, side1[cnt1 - 1].v, NULL);
            side1[cnt1++].v = p.j;
        } else if (p.j == side1[cnt1 - 1].v) {
            side1[cnt1 - 1].ts =
                addTri(side2[cnt2 - 1].v, p.i, side1[cnt1 - 1].ts);
            side2[cnt2 - 1].ts =
                addTri(side1[cnt1 - 1].v, p.i, side2[cnt2 - 1].ts);
            side2[cnt2].ts =
                addTri(side2[cnt2 - 1].v, side1[cnt1 - 1].v, NULL);
            side2[cnt2++].v = p.i;
        } else {
            side1[cnt1 - 1].ts =
                addTri(side2[cnt2 - 1].v, p.i, side1[cnt1 - 1].ts);
            side2[cnt2 - 1].ts =
                addTri(side1[cnt1 - 1].v, p.i, side2[cnt2 - 1].ts);
            side1[cnt1].ts =
                addTri(side2[cnt2 - 1].v, side1[cnt1 - 1].v, NULL);
            side1[cnt1++].v = p.i;
        }
        t = nxt;
    }
    side1[cnt1 - 1].ts = addTri(-2, side2[cnt2 - 1].v, side1[cnt1 - 1].ts);
    side2[cnt2 - 1].ts = addTri(-2, side1[cnt1 - 1].v, side2[cnt2 - 1].ts);
 
    /* store points in pts starting with t in 0, 
     * then side1, then s, then side2 
     */
    vmap = dtopen(&ipairdisc, Dtoset);
    vmapAdd(vmap, -1, 0);
    vmapAdd(vmap, -2, cnt1 + 1);
    pointf *pps = pts = gv_calloc(nt + 4, sizeof(pointf));
    tri **trim = gv_calloc(nt + 4, sizeof(tri*));
    *pps++ = p_t;
    idx = 1;
    for (int i = 0; i < cnt1; i++) {
        vmapAdd(vmap, side1[i].v, idx);
        *pps++ = rtr->ps[side1[i].v];
        trim[idx++] = side1[i].ts;
    }
    *pps++ = p_s;
    idx++;
    for (int i = cnt2 - 1; i >= 0; i--) {
        vmapAdd(vmap, side2[i].v, idx);
        *pps++ = rtr->ps[side2[i].v];
        trim[idx++] = side2[i].ts;
    }
 
    for (size_t i = 0; i < nt + 4; i++) {
        mapTri(vmap, trim[i]);
    }
 
    ps = gv_alloc(sizeof(tripoly_t));
    ps->poly.pn = nt + 4;  /* nt triangles gives nt+2 points plus s and t */
    ps->poly.ps = pts;
    ps->triMap = trim;
 
    free (side1);
    free (side2);
    dtclose(vmap);
    *sx = cnt1 + 1;             /* index of s in ps */
    return ps;
}
 
/* resetGraph:
 * Remove edges and nodes added for current edge routing
 */
static void resetGraph(tgraph *g, int ncnt, int ecnt,
                       size_t *original_edge_count) {
    int i;
    tnode *np = g->nodes;
    g->nedges = ecnt;
    for (i = 0; i < ncnt; i++) {
        np->ne = original_edge_count[i];
        np++;
    }
}
 
#define PQTYPE int
#define PQVTYPE float
 
#define PQ_TYPES
#include <neatogen/fPQ.h>
#undef PQ_TYPES
 
typedef struct {
    PQ pq;
    PQVTYPE *vals;
    int *idxs;
} PPQ;
 
#define N_VAL(pq,n) ((PPQ*)pq)->vals[n]
#define N_IDX(pq,n) ((PPQ*)pq)->idxs[n]
 
#define PQ_CODE
#include <neatogen/fPQ.h>
#undef PQ_CODE
 
#define N_DAD(n) dad[n]
#define E_WT(e) (e->dist)
#define UNSEEN (-FLT_MAX)
 
/* triPath:
 * Find the shortest path with lengths in g from
 * v0 to v1. The returned vector (dad) encodes the
 * shorted path from v1 to v0. That path is given by
 * v1, dad[v1], dad[dad[v1]], ..., v0.
 */
static int *
triPath(tgraph * g, int n, int v0, int v1, PQ * pq)
{
    int i, adjn;
    double d;
    tnode *np;
    tedge *e;
    int *dad = gv_calloc(n, sizeof(int));
 
    for (i = 0; i < pq->PQsize; i++)
        N_VAL(pq, i) = UNSEEN;
 
    PQinit(pq);
    N_DAD(v0) = -1;
    N_VAL(pq, v0) = 0;
    if (PQinsert(pq, v0))
        return NULL;
 
    while ((i = PQremove(pq)) != -1) {
        N_VAL(pq, i) *= -1;
        if (i == v1)
            break;
        np = g->nodes + i;
        for (size_t j = 0; j < np->ne; j++) {
            e = g->edges + np->edges[j];
            if (e->t == i)
                adjn = e->h;
            else
                adjn = e->t;
            if (N_VAL(pq, adjn) < 0) {
                d = -(N_VAL(pq, i) + E_WT(e));
                if (N_VAL(pq, adjn) == UNSEEN) {
                    N_VAL(pq, adjn) = d;
                    N_DAD(adjn) = i;
                    if (PQinsert(pq, adjn)) {
                       free(dad);
                       return NULL;
                    }
                } else if (N_VAL(pq, adjn) < d) {
                    PQupdate(pq, adjn, d);
                    N_DAD(adjn) = i;
                }
            }
        }
    }
    return dad;
}
 
/* makeMultiSpline:
 * FIX: we don't really use the shortest path provided by ED_path,
 * so avoid in neato spline code.
 * Return 0 on success.
 */
int makeMultiSpline(edge_t* e, router_t * rtr, int doPolyline) {
    Ppolyline_t line = ED_path(e);
    node_t *t = agtail(e);
    node_t *h = aghead(e);
    pointf t_p = line.ps[0];
    pointf h_p = line.ps[line.pn - 1];
    tripoly_t *poly;
    int idx;
    int *sp;
    int t_id = rtr->tn;
    int h_id = rtr->tn + 1;
    int ecnt = rtr->tg->nedges;
    PPQ pq;
    int ret;
 
    // record the number of edges in each node, so we can drop the added ones
    // later
    size_t *original_edge_count = gv_calloc(rtr->tg->nnodes,
                                            sizeof(original_edge_count[0]));
    for (size_t i = 0; i < rtr->tg->nnodes; ++i)
        original_edge_count[i] = rtr->tg->nodes[i].ne;
 
        /* Add endpoints to triangle graph */
    addEndpoint(rtr, t_p, t, t_id, ED_tail_port(e).side);
    addEndpoint(rtr, h_p, h, h_id, ED_head_port(e).side);
 
        /* Initialize priority queue */
    PQgen(&pq.pq, rtr->tn + 2, -1);
    PQTYPE *idxs = gv_calloc(pq.pq.PQsize + 1, sizeof(PQTYPE));
    PQVTYPE *vals = gv_calloc(pq.pq.PQsize + 1, sizeof(PQVTYPE));
    vals[0] = 0;
    pq.vals = vals + 1;
    pq.idxs = idxs + 1;
 
        /* Find shortest path of triangles */
    sp = triPath(rtr->tg, rtr->tn+2, h_id, t_id, (PQ *) & pq);
 
    free(vals);
    free(idxs);
    PQfree(&(pq.pq), 0);
 
        /* Use path of triangles to generate guiding polygon */
    if (sp) {
        poly = mkPoly(rtr, sp, h_id, t_id, h_p, t_p, &idx);
        free(sp);
 
        /* Generate multiple splines using polygon */
        ret = genroute(poly, idx, e, doPolyline);
        freeTripoly (poly);
    }
    else ret = -1;
 
    resetGraph(rtr->tg, rtr->tn, ecnt, original_edge_count);
    free(original_edge_count);
    return ret;
}