voronoi.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 <neatogen/mem.h>
#include <neatogen/geometry.h>
#include <neatogen/edges.h>
#include <neatogen/hedges.h>
#include <neatogen/heap.h>
#include <neatogen/voronoi.h>
 
void voronoi(Site *(*nextsite)(void *context), void *context) {
    Site *newsite, *bot, *top, *temp, *p;
    Site *v;
    Point newintstar = {0};
    char pm;
    Halfedge *lbnd, *rbnd, *llbnd, *rrbnd, *bisector;
    Edge *e;
 
    edgeinit();
    siteinit();
    pq_t *pq = PQinitialize();
    bottomsite = nextsite(context);
    ELinitialize();
 
    newsite = nextsite(context);
    while (1) {
        if (!PQempty(pq))
            newintstar = PQ_min(pq);
 
        if (newsite != NULL &&
      (PQempty(pq) || newsite->coord.y < newintstar.y ||
       (newsite->coord.y ==newintstar.y && newsite->coord.x < newintstar.x))) {
            /* new site is smallest */
            lbnd = ELleftbnd(&newsite->coord);
            rbnd = ELright(lbnd);
            bot = rightreg(lbnd);
            e = gvbisect(bot, newsite);
            bisector = HEcreate(e, le);
            ELinsert(lbnd, bisector);
            if ((p = hintersect(lbnd, bisector)) != NULL) {
                PQdelete(pq, lbnd);
                PQinsert(pq, lbnd, p, dist(p, newsite));
            }
            lbnd = bisector;
            bisector = HEcreate(e, re);
            ELinsert(lbnd, bisector);
            if ((p = hintersect(bisector, rbnd)) != NULL)
                PQinsert(pq, bisector, p, dist(p, newsite));
            newsite = nextsite(context);
        } else if (!PQempty(pq)) {
            /* intersection is smallest */
            lbnd = PQextractmin(pq);
            llbnd = ELleft(lbnd);
            rbnd = ELright(lbnd);
            rrbnd = ELright(rbnd);
            bot = leftreg(lbnd);
            top = rightreg(rbnd);
            v = lbnd->vertex;
            makevertex(v);
            endpoint(lbnd->ELedge, lbnd->ELpm, v);
            endpoint(rbnd->ELedge, rbnd->ELpm, v);
            ELdelete(lbnd);
            PQdelete(pq, rbnd);
            ELdelete(rbnd);
            pm = le;
            if (bot->coord.y > top->coord.y) {
                temp = bot;
                bot = top;
                top = temp;
                pm = re;
            }
            e = gvbisect(bot, top);
            bisector = HEcreate(e, pm);
            ELinsert(llbnd, bisector);
            endpoint(e, re - pm, v);
            deref(v);
            if ((p = hintersect(llbnd, bisector)) != NULL) {
                PQdelete(pq, llbnd);
                PQinsert(pq, llbnd, p, dist(p, bot));
            }
            if ((p = hintersect(bisector, rrbnd)) != NULL) {
                PQinsert(pq, bisector, p, dist(p, bot));
            }
        } else
            break;
    }
 
    for (lbnd = ELright(ELleftend); lbnd != ELrightend; lbnd = ELright(lbnd)) {
        e = lbnd->ELedge;
        clip_line(e);
    }
 
    // `PQcleanup` relies on the number of sites, so should be discarded and
    // at least every time we use `vAdjust`. See note in adjust.c:cleanup().
    PQcleanup(pq);
}