RendererHandle.h

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// ----------------------------------------------------------------------------
// -                        Open3D: www.open3d.org                            -
// ----------------------------------------------------------------------------
// Copyright (c) 2018-2023 www.open3d.org
// SPDX-License-Identifier: MIT
// ----------------------------------------------------------------------------
 
#pragma once
 
#include <fmt/format.h>
 
#include <array>
#include <cstdint>
#include <functional>
#include <type_traits>
 
namespace open3d {
 
namespace visualization {
namespace rendering {
 
// If you add entry here, don't forget to update TypeToString!
enum class EntityType : std::uint16_t {
    None = 0,
 
    View,
    Scene,
 
    Geometry,
    Light,
    IndirectLight,
    Skybox,
    Camera,
    Material,
    MaterialInstance,
    Texture,
    RenderTarget,
 
    VertexBuffer,
    IndexBuffer,
 
    Count
};
 
// RenderEntityHandle - handle type for entities inside Renderer
// Can be used in STL containers as key
struct REHandle_abstract {
    static const char* TypeToString(EntityType type);
 
    static const std::uint16_t kBadId = 0;
    const EntityType type = EntityType::None;
 
    inline size_t Hash() const {
        return static_cast<std::uint16_t>(type) << 16 | id;
    }
 
    bool operator==(const REHandle_abstract& other) const {
        return id == other.id && type == other.type;
    }
 
    bool operator!=(const REHandle_abstract& other) const {
        return !operator==(other);
    }
 
    bool operator<(const REHandle_abstract& other) const {
        return Hash() < other.Hash();
    }
 
    explicit operator bool() const { return id != kBadId; }
 
    REHandle_abstract() : type(EntityType::None), id(kBadId) {}
 
    std::uint16_t GetId() const { return id; }
 
protected:
    REHandle_abstract(const EntityType aType, const std::uint16_t aId)
        : type(aType), id(aId) {}
 
    static std::array<std::uint16_t, static_cast<size_t>(EntityType::Count)>
            uid_table;
 
    std::uint16_t id = kBadId;
};
 
std::ostream& operator<<(std::ostream& os, const REHandle_abstract& uid);
 
// REHandle is used for specification of handle types to prevent
// errors with passing, assigning or comparison of different kinds of handles
template <EntityType entityType>
struct REHandle : public REHandle_abstract {
    static const REHandle kBad;
 
    static REHandle Next() {
        const auto index = static_cast<std::uint16_t>(entityType);
        auto id = ++uid_table[index];
        if (id == REHandle_abstract::kBadId) {
            uid_table[index] = REHandle_abstract::kBadId + 1;
            id = REHandle_abstract::kBadId + 1;
        }
 
        return std::move(REHandle(id));
    }
 
    static REHandle Concretize(const REHandle_abstract& abstract) {
        if (abstract.type != entityType) {
            // assert("Incompatible render uid types!\n");
            return REHandle();
        }
 
        return REHandle(abstract.GetId());
    }
 
    REHandle() : REHandle_abstract(entityType, REHandle_abstract::kBadId) {}
    REHandle(const REHandle& other) : REHandle_abstract(entityType, other.id) {}
    // Don't use this constructor unless you know what you are doing
    explicit REHandle(std::uint16_t id) : REHandle_abstract(entityType, id) {}
 
    REHandle& operator=(const REHandle& other) {
        id = other.id;
        return *this;
    }
};
 
template <EntityType entityType>
const REHandle<entityType> REHandle<entityType>::kBad;
 
typedef REHandle<EntityType::View> ViewHandle;
typedef REHandle<EntityType::Scene> SceneHandle;
typedef REHandle<EntityType::Geometry> GeometryHandle;
typedef REHandle<EntityType::Light> LightHandle;
typedef REHandle<EntityType::IndirectLight> IndirectLightHandle;
typedef REHandle<EntityType::Skybox> SkyboxHandle;
typedef REHandle<EntityType::Camera> CameraHandle;
typedef REHandle<EntityType::Material> MaterialHandle;
typedef REHandle<EntityType::MaterialInstance> MaterialInstanceHandle;
typedef REHandle<EntityType::Texture> TextureHandle;
typedef REHandle<EntityType::RenderTarget> RenderTargetHandle;
typedef REHandle<EntityType::VertexBuffer> VertexBufferHandle;
typedef REHandle<EntityType::IndexBuffer> IndexBufferHandle;
 
}  // namespace rendering
}  // namespace visualization
}  // namespace open3d
 
namespace std {
template <>
class hash<open3d::visualization::rendering::REHandle_abstract> {
public:
    size_t operator()(const open3d::visualization::rendering::REHandle_abstract&
                              uid) const {
        return uid.Hash();
    }
};
}  // namespace std
 
namespace fmt {
template <typename T>
struct formatter<
        T,
        std::enable_if_t<std::is_base_of<open3d::visualization::rendering::
                                                 REHandle_abstract,
                                         T>::value,
                         char>> {
    template <typename FormatContext>
    auto format(const open3d::visualization::rendering::REHandle_abstract& uid,
                FormatContext& ctx) -> decltype(ctx.out()) {
        return format_to(ctx.out(), "[{}, {}, hash: {}]",
                         open3d::visualization::rendering::REHandle_abstract::
                                 TypeToString(uid.type),
                         uid.GetId(), uid.Hash());
    }
 
    template <typename ParseContext>
    constexpr auto parse(ParseContext& ctx) -> decltype(ctx.begin()) {
        return ctx.begin();
    }
};
}  // namespace fmt