FBPassthroughFeature.cs

//Copyright Icosa Foundation

using System;
using System.Runtime.InteropServices;
using AOT;
using UnityEditor;
using UnityEngine;
using UnityEngine.XR.OpenXR;
using UnityEngine.XR.OpenXR.Features;
#if UNITY_EDITOR
using UnityEditor.XR.OpenXR.Features;
#endif

namespace IcosaFoundation.OpenXR.Unity.FBPassthrough
{
    /// <summary>
    /// Example feature showing how to intercept a single OpenXR function.
    /// </summary>
    #if UNITY_EDITOR
    [OpenXRFeature(UiName = "Facebook Passthrough",
        BuildTargetGroups = new []{BuildTargetGroup.Standalone, BuildTargetGroup.WSA, BuildTargetGroup.Android},
        Company = "Icosa Foundation",
        Desc = "Implement XR_FB_passthrough without OVR SDK",
        OpenxrExtensionStrings = "XR_FB_passthrough",
        Version = "0.0.1",
        FeatureId = featureId)]
    #endif
    public class FBPassthroughFeature : OpenXRFeature
    {
        /// <summary>
        /// The feature id string. This is used to give the feature a well known id for reference.
        /// </summary>
        public const string featureId = "foundation.icosa.openxr-facebook-passthrough";

        /// <inheritdoc />
        protected override IntPtr HookGetInstanceProcAddr(IntPtr func)
        {
			return func;
        }

		private static ulong XrInstance = 0;
		private XrPassthroughFB activePassthrough = new XrPassthroughFB();
		private XrPassthroughLayerFB activeLayer = new XrPassthroughLayerFB();

        /// <inheritdoc />
        protected override bool OnInstanceCreate(ulong xrInstance)
        {
            // here's one way you can grab the instance
            XrInstance = xrInstance;
			var success = LoadBindings();
            return true;
        }

        /// <inheritdoc />
        protected override void OnSessionCreate(ulong xrSession)
        {
            // here's one way you can grab the session
            Debug.Log($"EXT: Got xrSession: {xrSession}");

			// Test activate
			var createSuccess = xrCreatePassthroughFB(
				xrSession,
				new XrPassthroughCreateInfoFB(XrPassthroughFlagsFB.IS_RUNNING_AT_CREATION_BIT_FB),
				out activePassthrough);
			var layerSuccess = xrCreatePassthroughLayerFB(xrSession, new XrPassthroughLayerCreateInfoFB(activePassthrough, XrPassthroughFlagsFB.IS_RUNNING_AT_CREATION_BIT_FB, XrPassthroughLayerPurposeFB.RECONSTRUCTION_FB), out activeLayer);
			
			XrCompositionLayerPassthroughFB layer = new XrCompositionLayerPassthroughFB(
				XrCompositionLayerFlags.BLEND_TEXTURE_SOURCE_ALPHA_BIT, activeLayer);
			// TODO: submit layer somehow
        }	

        protected override void OnSessionBegin (ulong xrSession)
        {
            Debug.Log($"EXT: xrBeginSession: {xrSession}");
        }

        protected override void OnSessionEnd(ulong xrSession)
        {
            Debug.Log($"EXT: about to xrEndSession: {xrSession}");
        }

		private delegate ulong GetInstanceProcAddrDelegate(ulong instance, string procName, out IntPtr procAddr);

		private static IntPtr GetFunction(string functionName)
		{
			var getInstanceProcAddr = Marshal.GetDelegateForFunctionPointer<GetInstanceProcAddrDelegate>(xrGetInstanceProcAddr);
			ulong result = getInstanceProcAddr(XrInstance, functionName, out var returnPtr);
			if (result < 0)
			{
				Debug.LogWarning($"Failed to find {functionName}");
				return IntPtr.Zero;
			}
			return returnPtr;
		}

#region OpenXR native bindings and types
// https://github.com/StereoKit/StereoKit/blob/master/Examples/StereoKitTest/Tools/PassthroughFBExt.cs

        enum XrStructureType : UInt64
		{
			XR_TYPE_PASSTHROUGH_CREATE_INFO_FB = 1000118001,
			XR_TYPE_PASSTHROUGH_LAYER_CREATE_INFO_FB = 1000118002,
			XR_TYPE_PASSTHROUGH_STYLE_FB = 1000118020,
			XR_TYPE_COMPOSITION_LAYER_PASSTHROUGH_FB = 1000118003,
		}

		enum XrPassthroughFlagsFB : UInt64
		{
			None = 0,
			IS_RUNNING_AT_CREATION_BIT_FB = 0x00000001
		}
		enum XrCompositionLayerFlags : UInt64
		{
			None = 0,
			CORRECT_CHROMATIC_ABERRATION_BIT = 0x00000001,
			BLEND_TEXTURE_SOURCE_ALPHA_BIT = 0x00000002,
			UNPREMULTIPLIED_ALPHA_BIT = 0x00000004,
		}
		enum XrPassthroughLayerPurposeFB : UInt32
		{
			RECONSTRUCTION_FB = 0,
			PROJECTED_FB = 1,
			TRACKED_KEYBOARD_HANDS_FB = 1000203001,
			MAX_ENUM_FB = 0x7FFFFFFF,
		}
		enum XrResult : UInt32
		{
			Success = 0,
		}

#pragma warning disable 0169 // handle is not "used", but required for interop
		struct XrPassthroughFB      { ulong handle; }
		struct XrPassthroughLayerFB { ulong handle; }
#pragma warning restore 0169

		[StructLayout(LayoutKind.Sequential)]
		struct XrPassthroughCreateInfoFB
		{
			private XrStructureType             type;
			public  IntPtr                      next;
			public  XrPassthroughFlagsFB        flags;

			public XrPassthroughCreateInfoFB(XrPassthroughFlagsFB passthroughFlags)
			{
				type  = XrStructureType.XR_TYPE_PASSTHROUGH_CREATE_INFO_FB;
				next  = IntPtr.Zero;
				flags = passthroughFlags;
			}
		}

		[StructLayout(LayoutKind.Sequential)]
		struct XrPassthroughLayerCreateInfoFB
		{
			private XrStructureType             type;
			public  IntPtr                      next;
			public  XrPassthroughFB             passthrough;
			public  XrPassthroughFlagsFB        flags;
			public  XrPassthroughLayerPurposeFB purpose;

			public XrPassthroughLayerCreateInfoFB(XrPassthroughFB passthrough, XrPassthroughFlagsFB flags, XrPassthroughLayerPurposeFB purpose)
			{
				type  = XrStructureType.XR_TYPE_PASSTHROUGH_LAYER_CREATE_INFO_FB;
				next  = IntPtr.Zero;
				this.passthrough = passthrough;
				this.flags       = flags;
				this.purpose     = purpose;
			}
		}

		[StructLayout(LayoutKind.Sequential)]
		struct XrPassthroughStyleFB
		{
			public XrStructureType             type;
			public IntPtr                      next;
			public float                       textureOpacityFactor;
			public Color                       edgeColor;
			public XrPassthroughStyleFB(float textureOpacityFactor, Color edgeColor)
			{
				type = XrStructureType.XR_TYPE_PASSTHROUGH_STYLE_FB;
				next = IntPtr.Zero;
				this.textureOpacityFactor = textureOpacityFactor;
				this.edgeColor            = edgeColor;
			}
		}
		[StructLayout(LayoutKind.Sequential)]
		struct XrCompositionLayerPassthroughFB
		{
			public XrStructureType             type;
			public IntPtr                      next;
			public XrCompositionLayerFlags     flags;
			public ulong                       space;
			public XrPassthroughLayerFB        layerHandle;
			public XrCompositionLayerPassthroughFB(XrCompositionLayerFlags flags, XrPassthroughLayerFB layerHandle)
			{
				type = XrStructureType.XR_TYPE_COMPOSITION_LAYER_PASSTHROUGH_FB;
				next = IntPtr.Zero;
				space = 0;
				this.flags = flags;
				this.layerHandle = layerHandle;
			}
		}

		delegate XrResult del_xrCreatePassthroughFB       (ulong session, [In] XrPassthroughCreateInfoFB createInfo, out XrPassthroughFB outPassthrough);
		delegate XrResult del_xrDestroyPassthroughFB      (XrPassthroughFB passthrough);
		delegate XrResult del_xrPassthroughStartFB        (XrPassthroughFB passthrough);
		delegate XrResult del_xrPassthroughPauseFB        (XrPassthroughFB passthrough);
		delegate XrResult del_xrCreatePassthroughLayerFB  (ulong session, [In] XrPassthroughLayerCreateInfoFB createInfo, out XrPassthroughLayerFB outLayer);
		delegate XrResult del_xrDestroyPassthroughLayerFB (XrPassthroughLayerFB layer);
		delegate XrResult del_xrPassthroughLayerPauseFB   (XrPassthroughLayerFB layer);
		delegate XrResult del_xrPassthroughLayerResumeFB  (XrPassthroughLayerFB layer);
		delegate XrResult del_xrPassthroughLayerSetStyleFB(XrPassthroughLayerFB layer, [In] XrPassthroughStyleFB style);

		del_xrCreatePassthroughFB        xrCreatePassthroughFB;
		del_xrDestroyPassthroughFB       xrDestroyPassthroughFB;
		del_xrPassthroughStartFB         xrPassthroughStartFB;
		del_xrPassthroughPauseFB         xrPassthroughPauseFB;
		del_xrCreatePassthroughLayerFB   xrCreatePassthroughLayerFB;
		del_xrDestroyPassthroughLayerFB  xrDestroyPassthroughLayerFB;
		del_xrPassthroughLayerPauseFB    xrPassthroughLayerPauseFB;
		del_xrPassthroughLayerResumeFB   xrPassthroughLayerResumeFB;
		del_xrPassthroughLayerSetStyleFB xrPassthroughLayerSetStyleFB;

		bool LoadBindings()
		{
			xrCreatePassthroughFB        = Marshal.GetDelegateForFunctionPointer<del_xrCreatePassthroughFB>       (GetFunction("xrCreatePassthroughFB"));
			xrDestroyPassthroughFB       = Marshal.GetDelegateForFunctionPointer<del_xrDestroyPassthroughFB>      (GetFunction("xrDestroyPassthroughFB"));
			xrPassthroughStartFB         = Marshal.GetDelegateForFunctionPointer<del_xrPassthroughStartFB>        (GetFunction("xrPassthroughStartFB"));
			xrPassthroughPauseFB         = Marshal.GetDelegateForFunctionPointer<del_xrPassthroughPauseFB>        (GetFunction("xrPassthroughPauseFB"));
			xrCreatePassthroughLayerFB   = Marshal.GetDelegateForFunctionPointer<del_xrCreatePassthroughLayerFB>  (GetFunction("xrCreatePassthroughLayerFB"));
			xrDestroyPassthroughLayerFB  = Marshal.GetDelegateForFunctionPointer<del_xrDestroyPassthroughLayerFB> (GetFunction("xrDestroyPassthroughLayerFB"));
			xrPassthroughLayerPauseFB    = Marshal.GetDelegateForFunctionPointer<del_xrPassthroughLayerPauseFB>   (GetFunction("xrPassthroughLayerPauseFB"));
			xrPassthroughLayerResumeFB   = Marshal.GetDelegateForFunctionPointer<del_xrPassthroughLayerResumeFB>  (GetFunction("xrPassthroughLayerResumeFB"));
			xrPassthroughLayerSetStyleFB = Marshal.GetDelegateForFunctionPointer<del_xrPassthroughLayerSetStyleFB>(GetFunction("xrPassthroughLayerSetStyleFB"));

			return
				xrCreatePassthroughFB        != null &&
				xrDestroyPassthroughFB       != null &&
				xrPassthroughStartFB         != null &&
				xrPassthroughPauseFB         != null &&
				xrCreatePassthroughLayerFB   != null &&
				xrDestroyPassthroughLayerFB  != null &&
				xrPassthroughLayerPauseFB    != null &&
				xrPassthroughLayerResumeFB   != null &&
				xrPassthroughLayerSetStyleFB != null;
		}
#endregion
    }
}