DYT/Tool/OpenSceneGraph-3.6.5/include/geos/geom/Quadrant.h

/**********************************************************************
 *
 * GEOS - Geometry Engine Open Source
 * http://geos.osgeo.org
 *
 * Copyright (C) 2005-2006 Refractions Research Inc.
 * Copyright (C) 2001-2002 Vivid Solutions Inc.
 *
 * This is free software; you can redistribute and/or modify it under
 * the terms of the GNU Lesser General Public Licence as published
 * by the Free Software Foundation.
 * See the COPYING file for more information.
 *
 **********************************************************************
 *
 * Last port: geom/Quadrant.java rev. 1.8 (JTS-1.10)
 *
 **********************************************************************/


#pragma once

#include <geos/export.h>
#include <geos/geom/Quadrant.h>
#include <geos/geom/Coordinate.h>
#include <geos/util/IllegalArgumentException.h>

#include <string>
#include <sstream>

// Forward declarations
namespace geos {
namespace geom {
class Coordinate;
}
}

namespace geos {
namespace geom { // geos.geom

/** \brief
 * Utility functions for working with quadrants.
 *
 * The quadrants are numbered as follows:
 * <pre>
 * 1 | 0
 * --+--
 * 2 | 3
 * </pre>
 *
 */
class GEOS_DLL Quadrant {

public:

    static const int NE = 0;
    static const int NW = 1;
    static const int SW = 2;
    static const int SE = 3;

    /**
     * Returns the quadrant of a directed line segment
     * (specified as x and y displacements, which cannot both be 0).
     *
     * @throws IllegalArgumentException if the displacements are both 0
     */
    static int quadrant(double dx, double dy)
    {
        if(dx == 0.0 && dy == 0.0) {
            std::ostringstream s;
            s << "Cannot compute the quadrant for point ";
            s << "(" << dx << "," << dy << ")" << std::endl;
            throw util::IllegalArgumentException(s.str());
        }
        if(dx >= 0) {
            if(dy >= 0) {
                return NE;
            }
            else {
                return SE;
            }
        }
        else {
            if(dy >= 0) {
                return NW;
            }
            else {
                return SW;
            }
        }
    };

    /**
     * Returns the quadrant of a directed line segment from p0 to p1.
     *
     * @throws IllegalArgumentException if the points are equal
     */
    static int quadrant(const geom::CoordinateXY& p0, const geom::CoordinateXY& p1)
    {
        if(p1.x == p0.x && p1.y == p0.y) {
            throw util::IllegalArgumentException("Cannot compute the quadrant for two identical points " + p0.toString());
        }

        if(p1.x >= p0.x) {
            if(p1.y >= p0.y) {
                return NE;
            }
            else {
                return SE;
            }
        }
        else {
            if(p1.y >= p0.y) {
                return NW;
            }
            else {
                return SW;
            }
        }
    };

    /**
     * Returns true if the quadrants are 1 and 3, or 2 and 4
     */
    static bool isOpposite(int quad1, int quad2)
    {
        if(quad1 == quad2) {
            return false;
        }
        int diff = (quad1 - quad2 + 4) % 4;
        // if quadrants are not adjacent, they are opposite
        if(diff == 2) {
            return true;
        }
        return false;
    };

    /*
     * Returns the right-hand quadrant of the halfplane defined by
     * the two quadrants,
     * or -1 if the quadrants are opposite, or the quadrant if they
     * are identical.
     */
    static int commonHalfPlane(int quad1, int quad2);

    /**
     * Returns whether the given quadrant lies within the given halfplane
     * (specified by its right-hand quadrant).
     */
    static bool isInHalfPlane(int quad, int halfPlane);

    /**
     * Returns true if the given quadrant is 0 or 1.
     */
    static bool isNorthern(int quad)
    {
        return quad == NE || quad == NW;
    };

};


} // namespace geos.geom
} // namespace geos