// Copyright (c) 2015 Barend Gehrels, Amsterdam, the Netherlands.
-// This file was modified by Oracle on 2017, 2018.
-// Modifications copyright (c) 2017-2018 Oracle and/or its affiliates.
+// This file was modified by Oracle on 2017-2021.
+// Modifications copyright (c) 2017-2021 Oracle and/or its affiliates.
// Contributed and/or modified by Adam Wulkiewicz, on behalf of Oracle
#define BOOST_GEOMETRY_ALGORITHMS_IS_CONVEX_HPP
-#include <boost/variant/apply_visitor.hpp>
-#include <boost/variant/static_visitor.hpp>
-#include <boost/variant/variant_fwd.hpp>
+#include <boost/range/empty.hpp>
#include <boost/geometry/algorithms/detail/equals/point_point.hpp>
+#include <boost/geometry/algorithms/detail/dummy_geometries.hpp>
+#include <boost/geometry/algorithms/detail/visit.hpp>
#include <boost/geometry/core/access.hpp>
#include <boost/geometry/core/closure.hpp>
#include <boost/geometry/core/cs.hpp>
#include <boost/geometry/core/coordinate_dimension.hpp>
+#include <boost/geometry/core/exterior_ring.hpp>
#include <boost/geometry/core/point_type.hpp>
+#include <boost/geometry/core/interior_rings.hpp>
+#include <boost/geometry/core/visit.hpp>
+#include <boost/geometry/geometries/adapted/boost_variant.hpp> // For backward compatibility
#include <boost/geometry/geometries/concepts/check.hpp>
#include <boost/geometry/iterators/ever_circling_iterator.hpp>
#include <boost/geometry/strategies/default_strategy.hpp>
-#include <boost/geometry/strategies/side.hpp>
-#include <boost/geometry/views/detail/normalized_view.hpp>
+#include <boost/geometry/strategies/is_convex/cartesian.hpp>
+#include <boost/geometry/strategies/is_convex/geographic.hpp>
+#include <boost/geometry/strategies/is_convex/spherical.hpp>
+#include <boost/geometry/views/detail/closed_clockwise_view.hpp>
namespace boost { namespace geometry
struct ring_is_convex
{
- template <typename Ring, typename SideStrategy>
- static inline bool apply(Ring const& ring, SideStrategy const& strategy)
+ template <typename Ring, typename Strategies>
+ static inline bool apply(Ring const& ring, Strategies const& strategies)
{
- typename SideStrategy::equals_point_point_strategy_type
- eq_pp_strategy = strategy.get_equals_point_point_strategy();
-
std::size_t n = boost::size(ring);
- if (boost::size(ring) < core_detail::closure::minimum_ring_size
- <
- geometry::closure<Ring>::value
- >::value)
+ if (n < detail::minimum_ring_size<Ring>::value)
{
// (Too) small rings are considered as non-concave, is convex
return true;
// Walk in clockwise direction, consider ring as closed
// (though closure is not important in this algorithm - any dupped
// point is skipped)
- typedef detail::normalized_view<Ring const> view_type;
- view_type view(ring);
+ using view_type = detail::closed_clockwise_view<Ring const>;
+ view_type const view(ring);
- typedef geometry::ever_circling_range_iterator<view_type const> it_type;
+ using it_type = geometry::ever_circling_range_iterator<view_type const>;
it_type previous(view);
it_type current(view);
current++;
+ auto const equals_strategy = strategies.relate(dummy_point(), dummy_point());
+
std::size_t index = 1;
- while (equals::equals_point_point(*current, *previous, eq_pp_strategy)
+ while (equals::equals_point_point(*current, *previous, equals_strategy)
&& index < n)
{
current++;
it_type next = current;
next++;
- while (equals::equals_point_point(*current, *next, eq_pp_strategy))
+ while (equals::equals_point_point(*current, *next, equals_strategy))
{
next++;
}
+ auto const side_strategy = strategies.side();
+
// We have now three different points on the ring
// Walk through all points, use a counter because of the ever-circling
// iterator
for (std::size_t i = 0; i < n; i++)
{
- int const side = strategy.apply(*previous, *current, *next);
+ int const side = side_strategy.apply(*previous, *current, *next);
if (side == 1)
{
// Next is on the left side of clockwise ring:
// Advance next to next different point
// (because there are non-equal points, this loop is not infinite)
next++;
- while (equals::equals_point_point(*current, *next, eq_pp_strategy))
+ while (equals::equals_point_point(*current, *next, equals_strategy))
{
next++;
}
};
+struct polygon_is_convex
+{
+ template <typename Polygon, typename Strategies>
+ static inline bool apply(Polygon const& polygon, Strategies const& strategies)
+ {
+ return boost::empty(interior_rings(polygon))
+ && ring_is_convex::apply(exterior_ring(polygon), strategies);
+ }
+};
+
+struct multi_polygon_is_convex
+{
+ template <typename MultiPolygon, typename Strategies>
+ static inline bool apply(MultiPolygon const& multi_polygon, Strategies const& strategies)
+ {
+ auto const size = boost::size(multi_polygon);
+ return size == 0 // For consistency with ring_is_convex
+ || (size == 1 && polygon_is_convex::apply(range::front(multi_polygon), strategies));
+ }
+};
+
+
}} // namespace detail::is_convex
#endif // DOXYGEN_NO_DETAIL
typename Geometry,
typename Tag = typename tag<Geometry>::type
>
-struct is_convex : not_implemented<Tag>
-{};
+struct is_convex
+{
+ template <typename Strategies>
+ static inline bool apply(Geometry const&, Strategies const&)
+ {
+ // Convexity is not defined for PointLike and Linear geometries.
+ // We could implement this because the following definitions would work:
+ // - no line segment between two points on the interior or boundary ever goes outside.
+ // - convex_hull of geometry is equal to the original geometry, this implies equal
+ // topological dimension.
+ // For MultiPoint we'd have to check whether or not an arbitrary number of equal points
+ // is stored.
+ // MultiPolygon we'd have to check for continuous chain of Linestrings which would require
+ // the use of relate(pt, seg) or distance(pt, pt) strategy.
+ return false;
+ }
+};
template <typename Box>
struct is_convex<Box, box_tag>
{
- template <typename Strategy>
- static inline bool apply(Box const& , Strategy const& )
+ template <typename Strategies>
+ static inline bool apply(Box const& , Strategies const& )
{
// Any box is convex (TODO: consider spherical boxes)
+ // TODO: in spherical and geographic the answer would be "false" most of the time.
+ // Assuming that:
+ // - it even makes sense to consider Box in spherical and geographic in this context
+ // because it's not a Polygon, e.g. it can degenerate to a Point.
+ // - line segments are defined by geodesics and box edges by parallels and meridians
+ // - we use this definition: A convex polygon is a simple polygon (not self-intersecting)
+ // in which no line segment between two points on the boundary ever goes outside the
+ // polygon.
+ // Then a geodesic segment would go into the exterior of a Box for all horizontal edges
+ // of a Box unless it was one of the poles (edge degenerated to a point) or equator and
+ // longitude difference was lesser than 360 (otherwise depending on the CS there would be
+ // no solution or there would be two possible solutions - segment going through one of
+ // the poles, at least in case of oblate spheroid, either way the answer would probably
+ // be "false").
return true;
}
};
-template <typename Box>
-struct is_convex<Box, ring_tag> : detail::is_convex::ring_is_convex
+template <typename Ring>
+struct is_convex<Ring, ring_tag> : detail::is_convex::ring_is_convex
+{};
+
+template <typename Polygon>
+struct is_convex<Polygon, polygon_tag> : detail::is_convex::polygon_is_convex
+{};
+
+template <typename MultiPolygon>
+struct is_convex<MultiPolygon, multi_polygon_tag> : detail::is_convex::multi_polygon_is_convex
{};
} // namespace dispatch
#endif // DOXYGEN_NO_DISPATCH
-namespace resolve_variant {
+namespace resolve_strategy {
-template <typename Geometry>
+template
+<
+ typename Strategies,
+ bool IsUmbrella = strategies::detail::is_umbrella_strategy<Strategies>::value
+>
struct is_convex
{
- template <typename Strategy>
+ template <typename Geometry>
+ static bool apply(Geometry const& geometry, Strategies const& strategies)
+ {
+ return dispatch::is_convex<Geometry>::apply(geometry, strategies);
+ }
+};
+
+template <typename Strategy>
+struct is_convex<Strategy, false>
+{
+ template <typename Geometry>
static bool apply(Geometry const& geometry, Strategy const& strategy)
{
- concepts::check<Geometry>();
- return dispatch::is_convex<Geometry>::apply(geometry, strategy);
+ using strategies::is_convex::services::strategy_converter;
+ return dispatch::is_convex
+ <
+ Geometry
+ >::apply(geometry, strategy_converter<Strategy>::get(strategy));
}
+};
- static bool apply(Geometry const& geometry, geometry::default_strategy const&)
+template <>
+struct is_convex<default_strategy, false>
+{
+ template <typename Geometry>
+ static bool apply(Geometry const& geometry, default_strategy const& )
{
- typedef typename strategy::side::services::default_strategy
+ typedef typename strategies::is_convex::services::default_strategy
<
- typename cs_tag<Geometry>::type
- >::type side_strategy;
+ Geometry
+ >::type strategy_type;
- return apply(geometry, side_strategy());
+ return dispatch::is_convex<Geometry>::apply(geometry, strategy_type());
}
};
-template <BOOST_VARIANT_ENUM_PARAMS(typename T)>
-struct is_convex<boost::variant<BOOST_VARIANT_ENUM_PARAMS(T)> >
+} // namespace resolve_strategy
+
+namespace resolve_dynamic {
+
+template <typename Geometry, typename Tag = typename tag<Geometry>::type>
+struct is_convex
{
template <typename Strategy>
- struct visitor: boost::static_visitor<bool>
+ static bool apply(Geometry const& geometry, Strategy const& strategy)
{
- Strategy const& m_strategy;
-
- visitor(Strategy const& strategy) : m_strategy(strategy) {}
+ concepts::check<Geometry>();
+ return resolve_strategy::is_convex<Strategy>::apply(geometry, strategy);
+ }
+};
- template <typename Geometry>
- bool operator()(Geometry const& geometry) const
+template <typename Geometry>
+struct is_convex<Geometry, dynamic_geometry_tag>
+{
+ template <typename Strategy>
+ static inline bool apply(Geometry const& geometry, Strategy const& strategy)
+ {
+ bool result = false;
+ traits::visit<Geometry>::apply([&](auto const& g)
{
- return is_convex<Geometry>::apply(geometry, m_strategy);
- }
- };
+ result = is_convex<util::remove_cref_t<decltype(g)>>::apply(g, strategy);
+ }, geometry);
+ return result;
+ }
+};
+// NOTE: This is a simple implementation checking if a GC contains single convex geometry.
+// Technically a GC could store e.g. polygons touching with edges and together creating a convex
+// region. To check this we'd require relate() strategy and the algorithm would be quite complex.
+template <typename Geometry>
+struct is_convex<Geometry, geometry_collection_tag>
+{
template <typename Strategy>
- static inline bool apply(boost::variant<BOOST_VARIANT_ENUM_PARAMS(T)> const& geometry,
- Strategy const& strategy)
+ static inline bool apply(Geometry const& geometry, Strategy const& strategy)
{
- return boost::apply_visitor(visitor<Strategy>(strategy), geometry);
+ bool result = false;
+ bool is_first = true;
+ detail::visit_breadth_first([&](auto const& g)
+ {
+ result = is_first
+ && is_convex<util::remove_cref_t<decltype(g)>>::apply(g, strategy);
+ is_first = false;
+ return result;
+ }, geometry);
+ return result;
}
};
-} // namespace resolve_variant
+} // namespace resolve_dynamic
// TODO: documentation / qbk
template<typename Geometry>
inline bool is_convex(Geometry const& geometry)
{
- return resolve_variant::is_convex
+ return resolve_dynamic::is_convex
<
Geometry
>::apply(geometry, geometry::default_strategy());
template<typename Geometry, typename Strategy>
inline bool is_convex(Geometry const& geometry, Strategy const& strategy)
{
- return resolve_variant::is_convex<Geometry>::apply(geometry, strategy);
+ return resolve_dynamic::is_convex<Geometry>::apply(geometry, strategy);
}
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