thejerf--baijiSteamVR/docs/Source/Core/VideoBackends/Vulkan/VulkanOpenXR.h

// Copyright 2024 Dolphin Emulator Project
// SPDX-License-Identifier: GPL-2.0-or-later

#pragma once

#ifdef ENABLE_VR

#include <array>
#include <memory>
#include <string>
#include <vector>

// VulkanLoader.h must come first — it defines VK_NO_PROTOTYPES before vulkan.h.
#include "VideoBackends/Vulkan/VulkanLoader.h"

#define XR_USE_GRAPHICS_API_VULKAN
#include <openxr/openxr.h>
#include <openxr/openxr_platform.h>

#include "VideoCommon/VR/OpenXRManager.h"

namespace Vulkan
{
class VKTexture;
class VKFramebuffer;

// Holds the swapchain images for one eye.
// The VkImage objects are owned by the OpenXR runtime; VKTexture wraps them
// (without allocation) and VKFramebuffer provides a render pass for rendering.
struct XRVkEyeSwapchain
{
  XrSwapchain swapchain = XR_NULL_HANDLE;
  uint32_t width = 0;
  uint32_t height = 0;

  // One entry per swapchain image.
  std::vector<std::unique_ptr<VKTexture>> textures;
  std::vector<std::unique_ptr<VKFramebuffer>> framebuffers;
};

// Vulkan-specific OpenXR backend. Implements VR::IOpenXRSwapchain so that
// Presenter::RenderXFBToScreen() can acquire/release eye images and submit
// frames using only VideoCommon-visible types (AbstractFramebuffer*).
// Vulkan extensions required by the OpenXR runtime, queried before VkInstance/VkDevice creation.
struct VulkanExtensionRequirements
{
  std::vector<std::string> instance_extensions;
  std::vector<std::string> device_extensions;
};

class VulkanOpenXR : public VR::IOpenXRSwapchain
{
public:
  VulkanOpenXR();
  ~VulkanOpenXR() override;

  VulkanOpenXR(const VulkanOpenXR&) = delete;
  VulkanOpenXR& operator=(const VulkanOpenXR&) = delete;

  // Must be called BEFORE VulkanContext::CreateVulkanInstance().
  // Creates a temporary XrInstance, queries the Vulkan extensions required by the
  // OpenXR runtime, and stores the OpenXRManager in VR::g_openxr for later reuse.
  static bool PreQueryVulkanExtensions(VulkanExtensionRequirements& out_requirements);

  // Full initialization: creates Vulkan-bound XrSession, reference space, and
  // per-eye swapchains. If PreQueryVulkanExtensions() was called, reuses the
  // existing VR::g_openxr; otherwise creates a new one.
  bool Initialize();

  // Tears down swapchains and resets g_openxr.
  void Shutdown();

  // ---- IOpenXRSwapchain ----

  // Acquire the next swapchain image for the given eye.
  // Returns AbstractFramebuffer* (actually VKFramebuffer*) to render into.
  AbstractFramebuffer* AcquireEyeFramebuffer(uint32_t eye_index) override;

  // Release the current swapchain image back to the runtime.
  void ReleaseEyeTexture(uint32_t eye_index) override;

  // Build the XrCompositionLayerProjection and call xrEndFrame.
  bool SubmitFrame() override;

  uint32_t GetEyeWidth() const override { return m_eye_swapchains[0].width; }
  uint32_t GetEyeHeight() const override { return m_eye_swapchains[0].height; }

  const XRVkEyeSwapchain& GetEyeSwapchain(uint32_t eye) const { return m_eye_swapchains[eye]; }

private:
  // Creates XrSession with XrGraphicsBindingVulkanKHR.
  bool CreateSessionVulkan();

  // Allocates m_eye_swapchains and wraps images as VKTexture / VKFramebuffer.
  bool CreateSwapchains();

  void DestroySwapchains();

  std::array<XRVkEyeSwapchain, 2> m_eye_swapchains{};

  // Image index selected by xrAcquireSwapchainImage for the current frame.
  std::array<uint32_t, 2> m_acquired_image_index{0, 0};
  std::array<bool, 2> m_image_acquired{false, false};

  // Reused per-frame composition data (avoids per-frame heap allocation).
  std::array<XrCompositionLayerProjectionView, 2> m_projection_views{};
  XrCompositionLayerProjection m_projection_layer{XR_TYPE_COMPOSITION_LAYER_PROJECTION};
};

// Global Vulkan OpenXR instance — valid between VideoBackend::Initialize() and Shutdown().
extern std::unique_ptr<VulkanOpenXR> g_openxr_vk;

}  // namespace Vulkan

#endif  // ENABLE_VR