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// Boost.Geometry (aka GGL, Generic Geometry Library)
// Copyright (c) 2014, Oracle and/or its affiliates.
// Contributed and/or modified by Menelaos Karavelas, on behalf of Oracle
// Licensed under the Boost Software License version 1.0.
// http://www.boost.org/users/license.html
#ifndef BOOST_GEOMETRY_ALGORITHMS_DETAIL_IS_VALID_RING_HPP
#define BOOST_GEOMETRY_ALGORITHMS_DETAIL_IS_VALID_RING_HPP
#include <boost/geometry/core/closure.hpp>
#include <boost/geometry/core/cs.hpp>
#include <boost/geometry/core/point_order.hpp>
#include <boost/geometry/util/order_as_direction.hpp>
#include <boost/geometry/util/range.hpp>
#include <boost/geometry/algorithms/equals.hpp>
#include <boost/geometry/views/reversible_view.hpp>
#include <boost/geometry/views/closeable_view.hpp>
#include <boost/geometry/algorithms/area.hpp>
#include <boost/geometry/algorithms/intersects.hpp>
#include <boost/geometry/algorithms/detail/is_valid/has_spikes.hpp>
#include <boost/geometry/algorithms/detail/is_valid/has_duplicates.hpp>
#include <boost/geometry/strategies/area.hpp>
namespace boost { namespace geometry
{
#ifndef DOXYGEN_NO_DETAIL
namespace detail { namespace is_valid
{
// struct to check whether a ring is topologically closed
template <typename Ring, closure_selector Closure /* open */>
struct is_topologically_closed
{
static inline bool apply(Ring const&)
{
return true;
}
};
template <typename Ring>
struct is_topologically_closed<Ring, closed>
{
static inline bool apply(Ring const& ring)
{
return geometry::equals(range::front(ring), range::back(ring));
}
};
template <typename ResultType, bool IsInteriorRing /* false */>
struct ring_area_predicate
{
typedef std::greater<ResultType> type;
};
template <typename ResultType>
struct ring_area_predicate<ResultType, true>
{
typedef std::less<ResultType> type;
};
template <typename Ring, bool IsInteriorRing>
struct is_properly_oriented
{
typedef typename point_type<Ring>::type point_type;
typedef typename strategy::area::services::default_strategy
<
typename cs_tag<point_type>::type,
point_type
>::type strategy_type;
typedef detail::area::ring_area
<
order_as_direction<geometry::point_order<Ring>::value>::value,
geometry::closure<Ring>::value
> ring_area_type;
typedef typename default_area_result<Ring>::type area_result_type;
static inline bool apply(Ring const& ring)
{
typename ring_area_predicate
<
area_result_type, IsInteriorRing
>::type predicate;
// Check area
area_result_type const zero = area_result_type();
return predicate(ring_area_type::apply(ring, strategy_type()), zero);
}
};
template
<
typename Ring,
bool AllowDuplicates,
bool CheckSelfIntersections = true,
bool IsInteriorRing = false
>
struct is_valid_ring
{
static inline bool apply(Ring const& ring)
{
// return invalid if any of the following condition holds:
// (a) the ring's size is below the minimal one
// (b) the ring is not topologically closed
// (c) the ring has spikes
// (d) the ring has duplicate points (if AllowDuplicates is false)
// (e) the boundary of the ring has self-intersections
// (f) the order of the points is inconsistent with the defined order
//
// Note: no need to check if the area is zero. If this is the
// case, then the ring must have at least two spikes, which is
// checked by condition (c).
closure_selector const closure = geometry::closure<Ring>::value;
return
( boost::size(ring)
>= core_detail::closure::minimum_ring_size<closure>::value )
&& is_topologically_closed<Ring, closure>::apply(ring)
&& (AllowDuplicates || !has_duplicates<Ring, closure>::apply(ring))
&& !has_spikes<Ring, closure>::apply(ring)
&& !(CheckSelfIntersections && geometry::intersects(ring))
&& is_properly_oriented<Ring, IsInteriorRing>::apply(ring);
}
};
}} // namespace dispatch
#endif // DOXYGEN_NO_DETAIL
#ifndef DOXYGEN_NO_DISPATCH
namespace dispatch
{
// A Ring is a Polygon with exterior boundary only.
// The Ring's boundary must be a LinearRing (see OGC 06-103-r4,
// 6.1.7.1, for the definition of LinearRing)
//
// Reference (for polygon validity): OGC 06-103r4 (6.1.11.1)
template <typename Ring, bool AllowSpikes, bool AllowDuplicates>
struct is_valid<Ring, ring_tag, AllowSpikes, AllowDuplicates>
: detail::is_valid::is_valid_ring<Ring, AllowDuplicates>
{};
} // namespace dispatch
#endif // DOXYGEN_NO_DISPATCH
}} // namespace boost::geometry
#endif // BOOST_GEOMETRY_ALGORITHMS_DETAIL_IS_VALID_RING_HPP
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