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1// Boost.Geometry (aka GGL, Generic Geometry Library)
2
3// Copyright (c) 2007-2015 Barend Gehrels, Amsterdam, the Netherlands.
4// Copyright (c) 2008-2015 Bruno Lalande, Paris, France.
5// Copyright (c) 2009-2015 Mateusz Loskot, London, UK.
6// Copyright (c) 2013-2015 Adam Wulkiewicz, Lodz, Poland.
7
8// This file was modified by Oracle on 2015.
9// Modifications copyright (c) 2015 Oracle and/or its affiliates.
10
11// Contributed and/or modified by Menelaos Karavelas, on behalf of Oracle
12
13// Use, modification and distribution is subject to the Boost Software License,
14// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
15// http://www.boost.org/LICENSE_1_0.txt)
16
17#ifndef BOOST_GEOMETRY_ALGORITHMS_DETAIL_POINT_IS_EQUAL_OR_SPIKE_HPP
18#define BOOST_GEOMETRY_ALGORITHMS_DETAIL_POINT_IS_EQUAL_OR_SPIKE_HPP
19
20#include <boost/geometry/algorithms/detail/direction_code.hpp>
21#include <boost/geometry/algorithms/detail/recalculate.hpp>
22#include <boost/geometry/policies/robustness/robust_point_type.hpp>
23#include <boost/geometry/strategies/side.hpp>
24#include <boost/geometry/util/condition.hpp>
25#include <boost/geometry/util/math.hpp>
26
27namespace boost { namespace geometry
28{
29
30
31#ifndef DOXYGEN_NO_DETAIL
32namespace detail
33{
34
35// Checks if a point ("last_point") causes a spike w.r.t.
36// the specified two other points (segment_a, segment_b)
37//
38// x-------x------x
39// a lp b
40//
41// Above, lp generates a spike w.r.t. segment(a,b)
42// So specify last point first, then (a,b)
43// The segment's orientation does matter: if lp is to the right of b
44// no spike is reported
45template <typename Point1, typename Point2, typename Point3>
46static inline bool point_is_spike_or_equal(Point1 const& last_point,
47 Point2 const& segment_a,
48 Point3 const& segment_b)
49{
50 typedef typename strategy::side::services::default_strategy
51 <
52 typename cs_tag<Point1>::type
53 >::type side_strategy;
54
55 int const side = side_strategy::apply(last_point, segment_a, segment_b);
56 if (side == 0)
57 {
58 // Last point is collinear w.r.t previous segment.
59 // Check if it is equal
60 int const sgn_x1 = sign_of_difference<0>(last_point, segment_b);
61 int const sgn_y1 = sign_of_difference<1>(last_point, segment_b);
62 if (sgn_x1 == 0 && sgn_y1 == 0)
63 {
64 return true;
65 }
66
67 // Check if it moves forward
68 int const sgn_x2 = sign_of_difference<0>(segment_b, segment_a);
69 int const sgn_y2 = sign_of_difference<1>(segment_b, segment_a);
70
71 return sgn_x1 != sgn_x2 || sgn_y1 != sgn_y2;
72 }
73 return false;
74}
75
76template
77<
78 typename Point1,
79 typename Point2,
80 typename Point3,
81 typename RobustPolicy
82>
83static inline bool point_is_spike_or_equal(Point1 const& last_point,
84 Point2 const& segment_a,
85 Point3 const& segment_b,
86 RobustPolicy const& robust_policy)
87{
88 if (point_is_spike_or_equal(last_point, segment_a, segment_b))
89 {
90 return true;
91 }
92
93 if (BOOST_GEOMETRY_CONDITION(! RobustPolicy::enabled))
94 {
95 return false;
96 }
97
98 // Try using specified robust policy
99 typedef typename geometry::robust_point_type
100 <
101 Point1,
102 RobustPolicy
103 >::type robust_point_type;
104
105 robust_point_type last_point_rob, segment_a_rob, segment_b_rob;
106 geometry::recalculate(last_point_rob, last_point, robust_policy);
107 geometry::recalculate(segment_a_rob, segment_a, robust_policy);
108 geometry::recalculate(segment_b_rob, segment_b, robust_policy);
109
110 return point_is_spike_or_equal
111 (
112 last_point_rob,
113 segment_a_rob,
114 segment_b_rob
115 );
116}
117
118
119} // namespace detail
120#endif
121
122}} // namespace boost::geometry
123
124
125#endif // BOOST_GEOMETRY_ALGORITHMS_DETAIL_POINT_IS_EQUAL_OR_SPIKE_HPP