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#pragma once
#include <mbgl/util/type_list.hpp>
#include <mbgl/util/indexed_tuple.hpp>
#include <array>
#include <cstddef>
#define MBGL_DEFINE_ATTRIBUTE(type_, n_, name_) \
struct name_ { \
using Type = ::mbgl::gfx::AttributeType<type_, n_>; \
static auto name() { \
return #name_; \
} \
}
namespace mbgl {
namespace gfx {
template <typename T, std::size_t N>
class AttributeType {
public:
using ValueType = T;
static constexpr size_t Dimensions = N;
using Value = std::array<T, N>;
};
// Attribute binding requires member offsets. The only standard way to
// obtain an offset is the offsetof macro. The offsetof macro has defined
// behavior only for standard layout types. That rules out std::tuple and
// any other solution that relies on chained inheritance. Manually implemented
// variadic specialization looks like the only solution. Fortunately, we
// only use a maximum of five attributes.
namespace detail {
template <class...>
class Vertex;
template <>
class Vertex<> {
public:
using VertexType = Vertex<>;
};
template <class A1>
class Vertex<A1> {
public:
A1 a1;
using VertexType = Vertex<A1>;
static const std::size_t attributeOffsets[1];
};
template <class A1, class A2>
class Vertex<A1, A2> {
public:
A1 a1;
A2 a2;
using VertexType = Vertex<A1, A2>;
static const std::size_t attributeOffsets[2];
};
template <class A1, class A2, class A3>
class Vertex<A1, A2, A3> {
public:
A1 a1;
A2 a2;
A3 a3;
using VertexType = Vertex<A1, A2, A3>;
static const std::size_t attributeOffsets[3];
};
template <class A1, class A2, class A3, class A4>
class Vertex<A1, A2, A3, A4> {
public:
A1 a1;
A2 a2;
A3 a3;
A4 a4;
using VertexType = Vertex<A1, A2, A3, A4>;
static const std::size_t attributeOffsets[4];
};
template <class A1, class A2, class A3, class A4, class A5>
class Vertex<A1, A2, A3, A4, A5> {
public:
A1 a1;
A2 a2;
A3 a3;
A4 a4;
A5 a5;
using VertexType = Vertex<A1, A2, A3, A4, A5>;
static const std::size_t attributeOffsets[5];
};
template <class A1>
const std::size_t Vertex<A1>::attributeOffsets[1] = {
offsetof(VertexType, a1)
};
template <class A1, class A2>
const std::size_t Vertex<A1, A2>::attributeOffsets[2] = {
offsetof(VertexType, a1),
offsetof(VertexType, a2)
};
template <class A1, class A2, class A3>
const std::size_t Vertex<A1, A2, A3>::attributeOffsets[3] = {
offsetof(VertexType, a1),
offsetof(VertexType, a2),
offsetof(VertexType, a3)
};
template <class A1, class A2, class A3, class A4>
const std::size_t Vertex<A1, A2, A3, A4>::attributeOffsets[4] = {
offsetof(VertexType, a1),
offsetof(VertexType, a2),
offsetof(VertexType, a3),
offsetof(VertexType, a4)
};
template <class A1, class A2, class A3, class A4, class A5>
const std::size_t Vertex<A1, A2, A3, A4, A5>::attributeOffsets[5] = {
offsetof(VertexType, a1),
offsetof(VertexType, a2),
offsetof(VertexType, a3),
offsetof(VertexType, a4),
offsetof(VertexType, a5)
};
template <class... As>
class Vertex<TypeList<As...>> {
public:
using VertexType = Vertex<typename As::Type::Value...>;
};
} // namespace detail
template <class A>
using Vertex = typename detail::Vertex<A>::VertexType;
} // namespace gfx
} // namespace mbgl
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