src/2geom/intersection.h

	intersection.h revision 76addc201c409e81eaaa73fe27cc0f79c4db097c
/**
 * \file
 * \brief Intersection utilities
 *//*
 * Authors:
 *   Krzysztof Kosiński <tweenk.pl@gmail.com>
 *
 * Copyright 2015 Authors
 *
 * This library is free software; you can redistribute it and/or
 * modify it either under the terms of the GNU Lesser General Public
 * License version 2.1 as published by the Free Software Foundation
 * (the "LGPL") or, at your option, under the terms of the Mozilla
 * Public License Version 1.1 (the "MPL"). If you do not alter this
 * notice, a recipient may use your version of this file under either
 * the MPL or the LGPL.
 *
 * You should have received a copy of the LGPL along with this library
 * in the file COPYING-LGPL-2.1; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 * You should have received a copy of the MPL along with this library
 * in the file COPYING-MPL-1.1
 *
 * The contents of this file are subject to the Mozilla Public License
 * Version 1.1 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY
 * OF ANY KIND, either express or implied. See the LGPL or the MPL for
 * the specific language governing rights and limitations.
 */

#ifndef SEEN_LIB2GEOM_INTERSECTION_H
#define SEEN_LIB2GEOM_INTERSECTION_H

#include <2geom/coord.h>
#include <2geom/point.h>

namespace Geom {


/** @brief Intersection between two shapes.
 */
template <typename TimeA = Coord, typename TimeB = TimeA>
class Intersection
{
public:
    /** @brief Construct from shape references and time values.
     * By default, the intersection point will be halfway between the evaluated
     * points on the two shapes. */
    template <typename TA, typename TB>
    Intersection(TA const &sa, TB const &sb, TimeA const &ta, TimeB const &tb)
        : first(ta)
        , second(tb)
        , _point(lerp(0.5, sa.pointAt(ta), sb.pointAt(tb)))
    {}

    /// Additionally report the intersection point.
    Intersection(TimeA const &ta, TimeB const &tb, Point const &p)
        : first(ta)
        , second(tb)
        , _point(p)
    {}

    /// Intersection point, as calculated by the intersection algorithm.
    Point point() const {
        return _point;
    }
    /// Implicit conversion to Point.
    operator Point() const {
        return _point;
    }

    friend inline void swap(Intersection &a, Intersection &b) {
        using std::swap;
        swap(a.first, b.first);
        swap(a.second, b.second);
        swap(a._point, b._point);
    }

public:
    /// First shape and time value.
    TimeA first;
    /// Second shape and time value.
    TimeB second;
private:
    // Recalculation of the intersection point from the time values is in many cases
    // less precise than the value obtained directly from the intersection algorithm,
    // so we need to store it.
    Point _point;
};


// TODO: move into new header
template <typename T>
struct ShapeTraits {
    typedef Coord TimeType;
    typedef Interval IntervalType;
    typedef T AffineClosureType;
    typedef Intersection<> IntersectionType;
};


} // namespace Geom

#endif // SEEN_LIB2GEOM_INTERSECTION_H
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