halfsegment.h

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/*
 * The MIT License (MIT)
 * Copyright (c) <2016> <Mark McKenney>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 * */


#include <iostream>
#ifndef HALFSEGMENT_H
#define HALFSEGMENT_H

//#define DEBUG_PRINT

using namespace std;

inline bool leftHandturn( double p1x, double p1y, double p2x, double p2y, double p3x, double p3y )
{
    // returns true if when you start at p1, and walk towards p2, you have to make a left turn
    // at p2 in order to continue walking to p3
    return( ( ((p3y - p1y) * (p2x - p1x)) - ((p2y - p1y) * (p3x - p1x)) ) > 0 );
}


struct halfsegment {
    double dx, dy, sx, sy; 
        int la, lb; 
        int stripID; 
        // the region this seg nelongs to
    int regionID;
    int ola, olb;
    
halfsegment():dx( 0 ), dy(0), sx(0), sy(0), la(-1), lb(-1),
        stripID(-1), regionID( -1 ), ola( -1 ), olb( -1 )
    { }

halfsegment( const halfsegment &rhs ): dx(rhs.dx), dy(rhs.dy),
        sx(rhs.sx), sy(rhs.sy), 
        la(rhs.la), lb(rhs.lb), 
        stripID( rhs.stripID), regionID( rhs.regionID ),
        ola( rhs.ola ), olb( rhs.olb )
            { }


    bool isLeft( ) const {
        return( dx < sx || (dx == sx && dy < sy ) );
    }

        halfsegment getBrother( ) const {
        halfsegment tmp( *this );
        tmp.dx = sx;
        tmp.dy = sy;
        tmp.sx = dx;
        tmp.sy = dy;
        return tmp;
    }

    bool operator==( const halfsegment &rhs ) const {
        return dx == rhs.dx && dy == rhs.dy && sx == rhs.sx && sy == rhs.sy;
    }

    bool operator<( const halfsegment &rhs ) const {
        if( dx < rhs.dx || (dx == rhs.dx && dy < rhs.dy ) ) return true;
        else if( dx == rhs.dx && dy == rhs.dy ) {
            // dom points the same
            if( isLeft() != rhs.isLeft( ) ) return !isLeft();
            // both left or right hsegs
            else if( this->colinear( rhs ) && (sx < rhs.sx || (sx == rhs.sx && sy < rhs.sy)) ) return true;
            else if( leftHandturn( dx, dy, sx, sy, rhs.sx, rhs.sy ) ) return true;
        }
        return false;
    }
    
    inline bool colinear( const halfsegment &rhs) const {
        return 0 == ( ((rhs.dy - dy) * (sx - dx)) - ((sy - dy) * (rhs.dx - dx)) ) &&
            0 == ( ((rhs.sy - dy) * (sx - dx)) - ((sy - dy) * (rhs.sx - dx)) ) ;
    }
    
    double getYvalAtX( const double x ) const 
    {
        if( x == dx )   return dy;
        else if( x == sx ) return sy;
        return( ( (sy*x - sy*dx - dy*x + dy*dx) / float((sx-dx))) + dy );
    }

    friend ostream & operator<<( ostream & out, const halfsegment & rhs ) {
        cerr <<"[(" << rhs.dx << "," << rhs.dy << ")(" << rhs.sx << "," << rhs.sy << ") " << rhs.la << ", " <<  rhs.lb << ", " << rhs.regionID << " <" << rhs.ola <<","<<rhs.olb<<">"<< "]";
        return out;
    }

};
#endif