daniel-lynch--ovrplugin-openxr-shim/shim

libOVRPlugin.so shim (OVRPlugin v1.51 ABI -> OpenXR)

Drop-in replacement for RE4 VR's libOVRPlugin.so. It re-exports the ovrp_* C ABI the game calls and implements it on OpenXR + Vulkan instead of Meta's libvrapi.so.

Status: working. RE4 VR boots and is playable on a Quest 2 through this shim on Meta's OpenXR runtime — stereo rendering, head and controller tracking, buttons, grips, haptics, and save loading. Steam Frame is the next target; see ../HOST.md.

Export surface

The artifact exports 438/438 ovrp_* symbols, matching ../analysis/all_exports.txt exactly (0 missing, 0 extra), so any dlsym of any ovrp_ resolves even for the ~199 entry points RE4 never references.

Source	Exports	What
src/stubs.c (generated)	371	103 Unsupported (-1004), 67 no-op Success (0), 201 NotYetImplemented (-1005)
src/core.c	46	lifecycle, frame loop, poses, controller, system info
src/layers.c	7	SetupLayer / GetLayerTexture2 / stage count / eye layer desc
src/vk_session.c	2	the Vulkan instance/device extension queries
src/passthru.c	12	trampolines for calls the game makes that need no real impl

gen_stubs.sh regenerates src/stubs.c from ../analysis/all_exports.txt; functions prototyped in the header are skipped there (67 of them) and implemented in core.c. Regeneration is deterministic — re-running it on a clean tree produces no diff.

Layout

• include/ovrplugin_shim.h — the ovrp_* C ABI: types, structs, core prototypes. Independently written against the observed ABI, with _Static_asserts pinning the binary-verified struct sizes so a layout mistake fails the build rather than the device.
• src/xr_runtime.{c,h} — the OpenXR engine: instance/session lifecycle, the frame loop, swapchains, layer composition, foveation, perf levels.
• src/vk_session.c — Vulkan graphics binding, image enumeration, the tile-memory flush.
• src/layers.c — layer setup and eye layer geometry.
• src/xr_input.c — action sets and controller/haptics mapping.
• src/android_init.c — JavaVM/activity capture, xrInitializeLoaderKHR, Android instance create-info chaining.
• src/passthru.c — the author-only A/B diagnostic (see below).
• src/stubs.c — generated.

Roughly 48 distinct OpenXR entry points are used.

Build

The deployable artifact is Android arm64 — the game runs inside Horizon OS or Lepton:

../scripts/fetch_deps.sh      # OpenXR + Vulkan headers, NDK, JDK, build-tools
./build_android.sh            # -> build/arm64/libOVRPlugin.so

Needs the NDK (r27c) and patchelf (to add NEEDED libopenxr_loader.so). Then ../packaging/repack.sh swaps it into your own dumped APK.

Host build is compile-validation plus the desktop OpenXR harness, not a shipping artifact:

./build_host.sh               # -> ../build/host/{libOVRPlugin.so,harness}
../tools/desktop-harness/run.sh

Needs libvulkan and an OpenXR loader; without the loader it builds the objects and stops.

Debug: passthru forwarding (author-only diagnostic)

debug.re4vr.passthru=1 hands the whole OVRPlugin session to a real, SONAME-patched libOVRPlugin_real.so if one is present in the APK — an A/B harness for diffing native runtime behaviour against the shim. No such binary is included or distributed by this repo; you would have to place one from your own device dump, and without it the flag is inert. All other debug.re4vr.* props are likewise diagnostics.

Known gaps

• Depth layer submission is gated behind debug.re4vr.depth and off by default; Meta's runtime accepts but does not use plain KHR depth for reprojection.
• Input binds /interaction_profiles/oculus/touch_controller only.
• Several debug.re4vr.* paths are documented dead ends kept for reference (copy-ring, render-ahead, submithook); see ../docs/research/ for what each one ruled out.

See ../docs/research/SHIM-SCOPE.md for how the surface was scoped, ../TESTING.md for the test plan, and ../docs/README.md for the research trail.