fs2open.github.com/code/graphics/openxr.cpp

#include "openxr_internal.h"

#include "camera/camera.h"
#include "graphics/2d.h"
#include "globalincs/version.h"
#include "mod_table/mod_table.h"
#include "render/3d.h"
#include "starfield/starfield.h"

#define XR_MAKE_VERSION_SHORT(major, minor, patch) \
    ((((major) & 0x3ffU) << 20) | (((minor) & 0x3ffU) << 10) | ((patch) & 0x3ffU))

bool openxr_req = false;
bool openxr_initialized = false;
bool openxr_recieve = false;

XrInstance xr_instance;
XrSystemId xr_system;
XrSession xr_session;
XrSpace xr_space;
XrTime xr_time;
XrDebugUtilsMessengerEXT xr_debugMessenger;
std::array<std::unique_ptr<XrSwapchainHandler>, 2> xr_swapchains;
std::array<XrView, 2> xr_views;
vec3d xr_offset = ZERO_VECTOR;
XrFrameState xr_state;
OpenXRFBStage xr_stage = OpenXRFBStage::NONE;
float xr_scale = 1.0f;

std::unique_ptr<star[]> Stars_XRBuffer;

static XrBool32 handleXRError(XrDebugUtilsMessageSeverityFlagsEXT severity, XrDebugUtilsMessageTypeFlagsEXT type, const XrDebugUtilsMessengerCallbackDataEXT* callbackData, void* /*userData*/) {
	SCP_string message;
	switch (type)
	{
	case XR_DEBUG_UTILS_MESSAGE_TYPE_GENERAL_BIT_EXT:
		message = "OpenXR: general\n%s";
		break;
	case XR_DEBUG_UTILS_MESSAGE_TYPE_VALIDATION_BIT_EXT:
		message = "OpenXR: validation\n%s";
		break;
	case XR_DEBUG_UTILS_MESSAGE_TYPE_PERFORMANCE_BIT_EXT:
		message = "OpenXR: performance\n%s";
		break;
	case XR_DEBUG_UTILS_MESSAGE_TYPE_CONFORMANCE_BIT_EXT:
		message = "OpenXR: conformance\n%s";
		break;
	}

	switch (severity)
	{
	case XR_DEBUG_UTILS_MESSAGE_SEVERITY_VERBOSE_BIT_EXT:
	case XR_DEBUG_UTILS_MESSAGE_SEVERITY_INFO_BIT_EXT:
		Information(LOCATION, message.c_str(), callbackData->message);
		break;
	case XR_DEBUG_UTILS_MESSAGE_SEVERITY_WARNING_BIT_EXT:
		Warning(LOCATION, message.c_str(), callbackData->message);
		break;
	case XR_DEBUG_UTILS_MESSAGE_SEVERITY_ERROR_BIT_EXT:
		Error(LOCATION, message.c_str(), callbackData->message);
		break;
	}

	return XR_FALSE;
}

void openxr_prepare(float hudscale) {
	Hud_global_scale = hudscale;
	openxr_req = true;
}

static bool openxr_init_instance() {
	auto extensions = gr_openxr_get_extensions();

	const gameversion::version& fso_version = gameversion::get_executable_version();
	const gameversion::version& mod_version(Mod_version);

#if !defined(NDEBUG)
	extensions.emplace_back("XR_EXT_debug_utils");
#endif

	XrInstanceCreateInfo instanceCreateInfo {
		XR_TYPE_INSTANCE_CREATE_INFO,
		nullptr,
		0,
		XrApplicationInfo {
			"", //Modname
			//Mod version. Should not contain negative numbers or only 0's.
			XR_MAKE_VERSION_SHORT(mod_version.major < 1 ? 1U : static_cast<uint32_t>(mod_version.major),
				mod_version.minor < 0 ? 0U : static_cast<uint32_t>(mod_version.minor),
				mod_version.build < 0 ? 0U : static_cast<uint32_t>(mod_version.build)),
			"FreeSpace Open",
			XR_MAKE_VERSION_SHORT(static_cast<uint32_t>(fso_version.major), static_cast<uint32_t>(fso_version.minor), static_cast<uint32_t>(fso_version.build)),
			XR_CURRENT_API_VERSION
		},
		0,
		nullptr,
		static_cast<uint32_t>(extensions.size()),
		extensions.data()
	};

	strncpy_s(instanceCreateInfo.applicationInfo.applicationName, Mod_title.empty() ? "FreeSpace Open" : Mod_title.c_str(), XR_MAX_APPLICATION_NAME_SIZE);

	if (xrCreateInstance(&instanceCreateInfo, &xr_instance) != XR_SUCCESS) {
		return false;
	}

#if !defined(NDEBUG)
	XrDebugUtilsMessengerCreateInfoEXT debugMessengerCreateInfo {
		XR_TYPE_DEBUG_UTILS_MESSENGER_CREATE_INFO_EXT,
		nullptr,
		XR_DEBUG_UTILS_MESSAGE_SEVERITY_INFO_BIT_EXT | XR_DEBUG_UTILS_MESSAGE_SEVERITY_WARNING_BIT_EXT | XR_DEBUG_UTILS_MESSAGE_SEVERITY_ERROR_BIT_EXT,
		XR_DEBUG_UTILS_MESSAGE_TYPE_GENERAL_BIT_EXT | XR_DEBUG_UTILS_MESSAGE_TYPE_VALIDATION_BIT_EXT | XR_DEBUG_UTILS_MESSAGE_TYPE_PERFORMANCE_BIT_EXT | XR_DEBUG_UTILS_MESSAGE_TYPE_CONFORMANCE_BIT_EXT,
		handleXRError,
		nullptr
	};

	openxr_callExtensionFunction<PFN_xrCreateDebugUtilsMessengerEXT>("xrCreateDebugUtilsMessengerEXT", xr_instance, &debugMessengerCreateInfo, &xr_debugMessenger);
#endif

	return true;
}

static bool openxr_init_system() {
	XrSystemGetInfo systemGetInfo {
	XR_TYPE_SYSTEM_GET_INFO,
	nullptr,
	XR_FORM_FACTOR_HEAD_MOUNTED_DISPLAY
	};

	if (xrGetSystem(xr_instance, &systemGetInfo, &xr_system) != XR_SUCCESS) {
		xr_system = XR_NULL_SYSTEM_ID;
		return false;
	}

	return true;
}

static bool openxr_init_swapchains() {
	uint32_t configurationViewsCount = 2;
	SCP_vector<XrViewConfigurationView> configurationViews(configurationViewsCount, { XR_TYPE_VIEW_CONFIGURATION_VIEW, nullptr, 0, 0, 0, 0, 0, 0 });

	if (xrEnumerateViewConfigurationViews(xr_instance, xr_system, XR_VIEW_CONFIGURATION_TYPE_PRIMARY_STEREO, configurationViewsCount, &configurationViewsCount, configurationViews.data()) != XR_SUCCESS) {
		return false;
	}

	uint32_t formatCount = 0;
	if (xrEnumerateSwapchainFormats(xr_session, 0, &formatCount, nullptr) != XR_SUCCESS) {
		return false;
	}

	SCP_vector<int64_t> formats(formatCount);
	if (xrEnumerateSwapchainFormats(xr_session, formatCount, &formatCount, formats.data()) != XR_SUCCESS) {
		return false;
	}

	int64_t chosenFormat = gr_openxr_get_swapchain_format(formats);

	std::array<XrSwapchain, 2> swapchains;
	for (uint32_t i = 0; i < 2; i++)
	{
		XrSwapchainCreateInfo swapchainCreateInfo {
			XR_TYPE_SWAPCHAIN_CREATE_INFO,
			nullptr,
			0,
			XR_SWAPCHAIN_USAGE_TRANSFER_DST_BIT,
			chosenFormat,
			1,
			configurationViews[i].recommendedImageRectWidth,
			configurationViews[i].recommendedImageRectHeight,
			1,
			1,
			1
		};

		if (xrCreateSwapchain(xr_session, &swapchainCreateInfo, &swapchains[i]) != XR_SUCCESS) {
			return false;
		}

		xr_swapchains[i].reset(new XrSwapchainHandler {
			swapchains[i],
			chosenFormat,
			configurationViews[i].recommendedImageRectWidth,
			configurationViews[i].recommendedImageRectHeight
		});
	}

	if (!gr_openxr_acquire_swapchain_buffers()) {
		return false;
	}

	return true;
}

static bool openxr_init_space() {
	XrReferenceSpaceCreateInfo spaceCreateInfo {
		XR_TYPE_REFERENCE_SPACE_CREATE_INFO,
		nullptr,
		XR_REFERENCE_SPACE_TYPE_LOCAL,
		XrPosef{ XrQuaternionf{ 0, 0, 0, 1 }, XrVector3f{ 0, 0, 0 } },
	};

	if (xrCreateReferenceSpace(xr_session, &spaceCreateInfo, &xr_space) != XR_SUCCESS) {
		return false;
	}

	return true;
}

static void openxr_init_post() {
	XrViewLocateInfo viewLocateInfo {
		XR_TYPE_VIEW_LOCATE_INFO,
		nullptr,
		XR_VIEW_CONFIGURATION_TYPE_PRIMARY_STEREO,
		xr_time,
		xr_space
	};

	XrViewState viewState {
		XR_TYPE_VIEW_STATE,
		nullptr,
		0
	};

	xr_views.fill({ XR_TYPE_VIEW, nullptr, XrPosef{}, XrFovf{} });
	uint32_t views;
	xrLocateViews(
		xr_session,
		&viewLocateInfo,
		&viewState,
		2,
		&views,
		xr_views.data()
	);

	VIEWER_ZOOM_DEFAULT = COCKPIT_ZOOM_DEFAULT = (fabsf(xr_views[0].fov.angleLeft) + fabsf(xr_views[0].fov.angleRight) + fabsf(xr_views[1].fov.angleLeft) + fabsf(xr_views[1].fov.angleRight)) / (2.0f * PROJ_FOV_FACTOR);

	
}

void openxr_init(float scale) {
	xr_scale = scale;

	if (!openxr_init_instance())
		return;

	if (!openxr_init_system())
		return;

	if (!gr_openxr_test_capabilities())
		return;

	//Non OpenGL backends, like vulkan, may need to query certain extensions to be enabled here as well

	if (!gr_openxr_create_session())
		return;
	
	if (!openxr_init_swapchains())
		return;

	if (!openxr_init_space())
		return;

	openxr_initialized = true;

	while (openxr_initialized && !openxr_recieve) {
		os_poll();
	}

	openxr_init_post();
}

void openxr_close() {
	xrDestroySpace(xr_space);
	for (auto& sc : xr_swapchains)
		sc.release();
	xrDestroySession(xr_session);

#if !defined(NDEBUG)
	openxr_callExtensionFunction<PFN_xrDestroyDebugUtilsMessengerEXT>("xrDestroyDebugUtilsMessengerEXT", xr_debugMessenger);
#endif

	xrDestroyInstance(xr_instance);
}

bool openxr_enabled() {
	return openxr_initialized && openxr_recieve;
}

bool openxr_requested() {
	return openxr_req;
}

void openxr_start_mission() {
	if (!openxr_initialized)
		return;

	xr_offset = ZERO_VECTOR;
	for (uint32_t i = 0; i < 2; i++) {
		const auto& pos = xr_views[i].pose.position;
		xr_offset += vec3d{ {pos.x * xr_scale, pos.y * xr_scale, pos.z * -xr_scale} };
	}
	xr_offset /= 2;

	if (!static_cast<bool>(Stars_XRBuffer))
		Stars_XRBuffer = make_unique<star[]>(MAX_STARS);

	extern std::unique_ptr<star[]> Stars;
	std::copy(Stars.get(), Stars.get() + MAX_STARS, Stars_XRBuffer.get());
}

void openxr_poll() {
	if (!openxr_initialized)
		return;

	XrEventDataBuffer eventData;
	eventData.type = XR_TYPE_EVENT_DATA_BUFFER;

	XrResult result = xrPollEvent(xr_instance, &eventData);
	if (result == XR_EVENT_UNAVAILABLE) {
		//No event
	}
	else if (result != XR_SUCCESS) {
		openxr_initialized = false;
		openxr_close();
	}
	else {
		switch (eventData.type)
		{
		case XR_TYPE_EVENT_DATA_INSTANCE_LOSS_PENDING:
			openxr_initialized = false;
			openxr_close();
			break;
		case XR_TYPE_EVENT_DATA_SESSION_STATE_CHANGED:
		{
			auto event = (XrEventDataSessionStateChanged*)&eventData;

			xr_time = event->time;

			switch (event->state)
			{
			case XR_SESSION_STATE_IDLE:
				openxr_recieve = false;
				break;
			case XR_SESSION_STATE_READY:
			{
				XrSessionBeginInfo sessionBeginInfo{
					XR_TYPE_SESSION_BEGIN_INFO,
					nullptr,
					XR_VIEW_CONFIGURATION_TYPE_PRIMARY_STEREO
				};

				if (xrBeginSession(xr_session, &sessionBeginInfo) != XR_SUCCESS) {
					openxr_initialized = false;
					openxr_close();
				}
			}
			/*fallthrough*/
			case XR_SESSION_STATE_SYNCHRONIZED:
			case XR_SESSION_STATE_VISIBLE:
			case XR_SESSION_STATE_FOCUSED:
				openxr_recieve = true;
				break;
			case XR_SESSION_STATE_STOPPING:
				xrEndSession(xr_session);
			/*fallthrough*/
			case XR_SESSION_STATE_LOSS_PENDING:
			case XR_SESSION_STATE_EXITING:
				openxr_initialized = false;
				openxr_close();
				break;
			default:
				break;
			}
			break;
		}
		default:
			break;
		}
	}
}

OpenXRTrackingInfo openxr_start_stereo_frame() {
	if (!openxr_initialized)
		return OpenXRTrackingInfo{};

	xr_stage = OpenXRFBStage::FIRST;

	openxr_start_frame();

	OpenXRTrackingInfo info{};

	for (uint32_t i = 0; i < 2; i++) {
		const auto& pos = xr_views[i].pose.position;
		const auto& ori = xr_views[i].pose.orientation;
		info.eyes[i].offset = vec3d{ {pos.x * xr_scale, pos.y * xr_scale, pos.z * -xr_scale} } - xr_offset;

		matrix asymmetric_fov, orientation;
		angles fix_asymmetric_fov{ 0, 0, xr_views[i].fov.angleLeft + xr_views[i].fov.angleRight };
		vm_quaternion_to_matrix(&orientation, ori.x, ori.y, -ori.z, -ori.w);
		vm_angles_2_matrix(&asymmetric_fov, &fix_asymmetric_fov);
		vm_matrix_x_matrix(&info.eyes[i].orientation, &orientation, &asymmetric_fov);
	}

	return info;
}

//Internal Helper functions

void openxr_start_frame() {
	XrFrameWaitInfo frameWaitInfo {
		XR_TYPE_FRAME_WAIT_INFO,
		nullptr
	};
	xr_state = XrFrameState {
		XR_TYPE_FRAME_STATE,
		nullptr,
		0,
		0,
		0
	};

	xrWaitFrame(xr_session, &frameWaitInfo, &xr_state);

	XrViewLocateInfo viewLocateInfo {
		XR_TYPE_VIEW_LOCATE_INFO,
		nullptr,
		XR_VIEW_CONFIGURATION_TYPE_PRIMARY_STEREO,
		xr_state.predictedDisplayTime,
		xr_space
	};

	xr_time = xr_state.predictedDisplayTime;

	XrViewState viewState {
		XR_TYPE_VIEW_STATE,
		nullptr,
		0
	};

	xr_views.fill({ XR_TYPE_VIEW, nullptr, XrPosef{}, XrFovf{} });

	uint32_t views;
	xrLocateViews(
		xr_session,
		&viewLocateInfo,
		&viewState,
		2,
		&views,
		xr_views.data()
	);

	XrFrameBeginInfo beginFrameInfo{ XR_TYPE_FRAME_BEGIN_INFO, nullptr };
	xrBeginFrame(xr_session, &beginFrameInfo);
}