MySQL 8.0.29
Source Code Documentation
ring_flip_visitor.h
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1#ifndef SQL_GIS_RING_FLIP_VISITOR_H_INCLUDED
2#define SQL_GIS_RING_FLIP_VISITOR_H_INCLUDED
3
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25
26#include <boost/geometry.hpp>
27#include <memory> // std::unique_ptr
28
29#include "sql/dd/types/spatial_reference_system.h" // dd::Spatial_reference_system
33
34namespace gis {
35
36/// A visitor that flips polygon rings so that exterior rings are in a
37/// counter-clockwise direction and interior rings in a clockwise direction.
38///
39/// Invalid polygon rings are not guaranteed to be flipped to the correct
40/// direction.
42 private:
43 /// Strategy used for geographic SRSs.
44 std::unique_ptr<boost::geometry::strategy::area::geographic<>>
46 /// Whether the geometry is invalid. That happens either if the ellipsoid of
47 /// a geographic SRS is invalid or if we encounter a ring with unknown
48 /// direction.
50
51 public:
52 /// Construct a new ring flip visitor.
53 ///
54 /// @param[in] semi_major The semi-major axis of the ellipsoid.
55 /// @param[in] semi_minor The semi-minor axis of the ellipsoid.
56 Ring_flip_visitor(double semi_major, double semi_minor) {
57 try {
59 new boost::geometry::strategy::area::geographic<>(
60 boost::geometry::srs::spheroid<double>(semi_major, semi_minor)));
61 m_invalid = false;
62 } catch (...) {
63 // Spheroid construction may fail if the axes are invalid.
64 m_invalid = true;
65 }
66 }
67
68 /// Check if anything wrong has been detected, either an invalid ellipsoid or
69 /// a ring with an unknown direction.
70 ///
71 /// Polygon rings which direction can't be determined are invalid. This is the
72 /// only way this visitor detects invalid rings. Other invalid rings, e.g.,
73 /// rings crossing themselves, are not necessarily detected.
74 ///
75 /// @retval true Invalid SRS ellipsoid or invalid polygon ring.
76 /// @retval false No invalid rings detected, but the geometry may still be
77 /// invalid.
78 bool invalid() const { return m_invalid; }
79
81 bool visit_enter(Polygon *py) override;
82 bool visit_enter(Multipolygon *py) override;
83
84 bool visit_enter(Multipoint *) override {
85 return true; // Don't descend into each point.
86 }
87
88 bool visit_enter(Multilinestring *) override {
89 return true; // Don't descend into each linestring.
90 }
91};
92
93} // namespace gis
94
95#endif // SQL_GIS_RING_FLIP_VISITOR_H_INCLUDED
A colletion of linestrings.
Definition: geometries.h:522
A collection of points.
Definition: geometries.h:483
A collection of polygons.
Definition: geometries.h:563
A visitor that implements the entire interface and does nothing.
Definition: geometry_visitor.h:121
bool visit_enter(Geometry *) override
Enters a compound geometry.
Definition: geometry_visitor.h:123
A polygon consisting of an outer ring and zero or more interior rings defining holes in the polygon.
Definition: geometries.h:348
A visitor that flips polygon rings so that exterior rings are in a counter-clockwise direction and in...
Definition: ring_flip_visitor.h:41
bool visit_enter(Polygon *py) override
Definition: ring_flip_visitor.cc:33
bool visit_enter(Multilinestring *) override
Definition: ring_flip_visitor.h:88
std::unique_ptr< boost::geometry::strategy::area::geographic<> > m_geographic_strategy
Strategy used for geographic SRSs.
Definition: ring_flip_visitor.h:45
bool visit_enter(Multipoint *) override
Definition: ring_flip_visitor.h:84
bool m_invalid
Whether the geometry is invalid.
Definition: ring_flip_visitor.h:49
bool invalid() const
Check if anything wrong has been detected, either an invalid ellipsoid or a ring with an unknown dire...
Definition: ring_flip_visitor.h:78
Ring_flip_visitor(double semi_major, double semi_minor)
Construct a new ring flip visitor.
Definition: ring_flip_visitor.h:56
This file declares the coordinate system specific subclasses of the geometry class hierarchy.
This file contains Boost.Geometry type traits declarations for Cartesian and geographic geometries.
The geometries implement a hierarchical visitor pattern.
Definition: area.cc:46