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++ // Copyright (c) 2017-2026 The Khronos Group Inc.
++ // Copyright (c) 2017-2019 Valve Corporation
++ // Copyright (c) 2017-2019 LunarG, Inc.
++ //
++ // SPDX-License-Identifier: Apache-2.0 OR MIT
++ //
++ // Initial Author: Mark Young <marky@lunarg.com>
++ //
++
++ #pragma once
++
++ #include "extra_algorithms.h"
++
++ #include <openxr/openxr.h>
++ #include <openxr/openxr_loader_negotiation.h>
++
++ #include <array>
++ #include <cmath>
++ #include <memory>
++ #include <mutex>
++ #include <string>
++ #include <unordered_map>
++ #include <vector>
++
++ class ApiLayerInterface;
++ struct XrGeneratedDispatchTableCore;
++ class LoaderInstance;
++
++ // Manage the single loader instance that is available.
++ namespace ActiveLoaderInstance {
++ // Set the active loader instance. This will fail if there is already an active loader instance.
++ XrResult Set(std::unique_ptr<LoaderInstance> loader_instance, const char* log_function_name);
++
++ // Returns true if there is an active loader instance.
++ bool IsAvailable();
++
++ // Get the active LoaderInstance.
++ XrResult Get(LoaderInstance** loader_instance, const char* log_function_name);
++
++ // Destroy the currently active LoaderInstance if there is one. This will make the loader able to create a new XrInstance if needed.
++ void Remove();
++ }; // namespace ActiveLoaderInstance
++
++ // Manages information needed by the loader for an XrInstance, such as what extensions are available and the dispatch table.
++ class LoaderInstance {
++ public:
++ // Factory method
++ static XrResult CreateInstance(PFN_xrGetInstanceProcAddr get_instance_proc_addr_term, PFN_xrCreateInstance create_instance_term,
++ PFN_xrCreateApiLayerInstance create_api_layer_instance_term,
++ std::vector<std::unique_ptr<ApiLayerInterface>> layer_interfaces,
++ const XrInstanceCreateInfo* createInfo, std::unique_ptr<LoaderInstance>* loader_instance);
++ static const std::array<XrExtensionProperties, 1>& LoaderSpecificExtensions();
++
++ virtual ~LoaderInstance();
++
++ XrInstance GetInstanceHandle() const { return _runtime_instance; }
++ const std::unique_ptr<XrGeneratedDispatchTableCore>& DispatchTable() const { return _dispatch_table; }
++ std::vector<std::unique_ptr<ApiLayerInterface>>& LayerInterfaces() { return _api_layer_interfaces; }
++ bool ExtensionIsEnabled(const std::string& extension) const;
++ XrDebugUtilsMessengerEXT DefaultDebugUtilsMessenger() const { return _messenger; }
++ void SetDefaultDebugUtilsMessenger(XrDebugUtilsMessengerEXT messenger) { _messenger = messenger; }
++ XrResult GetInstanceProcAddr(const char* name, PFN_xrVoidFunction* function);
++
++ private:
++ LoaderInstance(XrInstance instance, const XrInstanceCreateInfo* createInfo, PFN_xrGetInstanceProcAddr topmost_gipa,
++ std::vector<std::unique_ptr<ApiLayerInterface>> api_layer_interfaces);
++
++ private:
++ XrInstance _runtime_instance{XR_NULL_HANDLE};
++ PFN_xrGetInstanceProcAddr _topmost_gipa{nullptr};
++ std::vector<std::string> _enabled_extensions;
++ std::vector<std::unique_ptr<ApiLayerInterface>> _api_layer_interfaces;
++
++ std::unique_ptr<XrGeneratedDispatchTableCore> _dispatch_table;
++ // Internal debug messenger created during xrCreateInstance
++ XrDebugUtilsMessengerEXT _messenger{XR_NULL_HANDLE};
++ };