line-geometry.h

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// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Routines for dealing with lines (intersections, etc.)
 *
 * Authors:
 *   Maximilian Albert <Anhalter42@gmx.de>
 *
 * Copyright (C) 2007 authors
 *
 * Released under GNU GPL v2+, read the file 'COPYING' for more information.
 */
 
#ifndef SEEN_LINE_GEOMETRY_H
#define SEEN_LINE_GEOMETRY_H
 
#include <2geom/point.h>
#include <optional>
 
#include "axis-manip.h" // FIXME: This is only for Box3D::epsilon; move that to a better location
#include "object/persp3d.h"
 
class SPDesktop;
typedef unsigned int guint32;
 
namespace Box3D {
 
class Line {
public:
    Line(Geom::Point const &start, Geom::Point const &vec, bool is_endpoint = true);
    Line(Line const &line);
    virtual ~Line() = default;
    Line &operator=(Line const &line);
    virtual std::optional<Geom::Point> intersect(Line const &line);
    inline Geom::Point direction () { return v_dir; }
    
    Geom::Point closest_to(Geom::Point const &pt); // returns the point on the line closest to pt 
 
    friend inline std::ostream &operator<< (std::ostream &out_file, const Line &in_line);
    std::optional<Geom::Point> intersection_with_viewbox (SPDesktop *desktop);
    inline bool lie_on_same_side (Geom::Point const &A, Geom::Point const &B) {
        /* If A is a point in the plane and n is the normal vector of the line then
           the sign of dot(A, n) specifies the half-plane in which A lies.
           Thus A and B lie on the same side if the dot products have equal sign. */
        return ((Geom::dot(A, normal) - d0) * (Geom::dot(B, normal) - d0)) > 0;
    }
 
    double lambda (Geom::Point const pt);
    inline Geom::Point point_from_lambda (double const lambda) { 
        return (pt + lambda * Geom::unit_vector (v_dir)); }
 
protected:
    void set_direction(Geom::Point const &dir);
    inline static bool pts_coincide (Geom::Point const pt1, Geom::Point const pt2)
    {
        return (Geom::L2 (pt2 - pt1) < epsilon);
    }
 
    Geom::Point pt;
    Geom::Point v_dir;
    Geom::Point normal;
    Geom::Coord d0;
};
 
inline double determinant (Geom::Point const &a, Geom::Point const &b)
{
    return (a[Geom::X] * b[Geom::Y] - a[Geom::Y] * b[Geom::X]);
}
std::pair<double, double> coordinates (Geom::Point const &v1, Geom::Point const &v2, Geom::Point const &w);
bool lies_in_sector (Geom::Point const &v1, Geom::Point const &v2, Geom::Point const &w);
bool lies_in_quadrangle (Geom::Point const &A, Geom::Point const &B, Geom::Point const &C, Geom::Point const &D, Geom::Point const &pt);
std::pair<Geom::Point, Geom::Point> side_of_intersection (Geom::Point const &A, Geom::Point const &B,
                                                          Geom::Point const &C, Geom::Point const &D,
                                                          Geom::Point const &pt, Geom::Point const &dir);
 
inline std::ostream &operator<< (std::ostream &out_file, const Line &in_line) {
    out_file << "Start: " << in_line.pt << "  Direction: " << in_line.v_dir;
    return out_file;
}
 
} // namespace Box3D
 
 
#endif /* !SEEN_LINE_GEOMETRY_H */
 
/*
  Local Variables:
  mode:c++
  c-file-style:"stroustrup"
  c-file-offsets:((innamespace . 0)(inline-open . 0))
  indent-tabs-mode:nil
  fill-column:99
  End:
*/
// vim: filetype=cpp:expandtab:shiftwidth=4:tabstop=8:softtabstop=4 :