inpoly.c

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/* $Id$ $Revision$ */
/* 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/
 *************************************************************************/

/* 
 * in_poly
 * 
 * Test if a point is inside a polygon.
 * The polygon must be convex with vertices in CW order.
 */

#include <stdlib.h>
#include "vispath.h"
#include "pathutil.h"

#ifdef DMALLOC
#include "dmalloc.h"
#endif

int in_poly(Ppoly_t poly, Ppoint_t q)
{
    int i, i1;                  /* point index; i1 = i-1 mod n */
    int n;
    Ppoint_t *P;

    P = poly.ps;
    n = poly.pn;
    for (i = 0; i < n; i++) {
        i1 = (i + n - 1) % n;
        if (wind(P[i1],P[i],q) == 1) return FALSE;
    }
    return TRUE;
}