vr: add OpenXR headset output, VR tracker and VR controller input behind --vr (#1726)

src/libs/hmd2.h

@@ -12,6 +12,17 @@ inline constexpr uint64_t OUTPUT_MODE_89_91HZ  = 0x2000c;
 inline constexpr uint64_t OUTPUT_MODE_119_88HZ = 0x2000f;
 inline constexpr int32_t ERROR_REPROJECTION_NOT_INITIALIZED = -1972240373; // 0x8a72000b
 
+// Virtual ER15 field of view per eye: 55/42.5/51.2/51.2 degrees. "Out" is the temporal side and
+// "in" the nasal side. These tangents describe that geometry, not bit-exact firmware output.
+inline constexpr float FOV_TAN_OUT    = 1.4281480312f;
+inline constexpr float FOV_TAN_IN     = 0.9163311720f;
+inline constexpr float FOV_TAN_TOP    = 1.2437491417f;
+inline constexpr float FOV_TAN_BOTTOM = 1.2437491417f;
+
+// Each eye sits half the lens separation to the side of the head.
+inline constexpr uint8_t LENS_SEPARATION_MM = 63;
+inline constexpr float   EYE_OFFSET_M       = LENS_SEPARATION_MM / 2000.0f;
+
 struct ReprojectionState {
 	std::atomic<uint64_t> output_mode {0};
 	std::atomic<uint32_t> timing_us {3000};
@@ -19,6 +30,24 @@ struct ReprojectionState {
 
 [[nodiscard]] ReprojectionState* GetReprojectionState();
 
+struct SceFVector3 {
+	float x;
+	float y;
+	float z;
+};
+
+// The headset video-out port registers SceHmd2ReprojectionBuffer objects. The eye texture of their
+// first layer is the surface the game flips; both eyes sit side by side in it.
+struct ReprojectionSurface {
+	uint64_t address;
+	uint32_t width;
+	uint32_t height;
+	uint64_t pixel_format; // SceVideoOutPixelFormat
+};
+
+[[nodiscard]] bool GetReprojectionSurface(const void*          reprojection_buffer,
+                                          ReprojectionSurface& out);
+
 } // namespace Libs::Hmd2
 
 #endif // EMULATOR_SRC_LIBS_HMD2_H_