daniel-lynch--ovrplugin-openxr-shim/docs/research/related-work.md

Related work — how others run Quest games elsewhere, and why this shim is different

A survey of the projects in the same space, why none of them is what this repo is, and what (little) we'd adopt from them. Based on public repos + black-box surface inspection of publicly-distributed binaries — no decompilation of anyone's proprietary internals.

TL;DR

There is no public, open-source reimplementation of libOVRPlugin.so on OpenXR. A whole-of-GitHub search for ovrplugin returns three repos, none a shim. The one tool that runs VrApi/OVRPlugin Quest games on other headsets — Overport — does it by redistributing Meta's own newer OVRPlugin binary plus a vendor OpenXR loader, not by reimplementing anything. So this project (a clean-room, from-scratch ovrp_* engine on OpenXR) appears to be the only open implementation of that translation layer.

Overport (ovrport/app)

GPLv3, Kotlin/Compose, ~349★. Two halves, only one of which is open:

1. The patcher (open, in the repo). A Compose Multiplatform + ARSCLib app/CLI that rewrites a Quest APK: strips entitlements (via injected Frida scripts + a SKU/asset config), fixes the manifest, swaps icons/labels, and applies engine-specific smali patches. Its VR-library handling is three tiny patches:

   • CopyOVRPluginVrApiPatch — drop a bundled libOVRPlugin.so into any game that has libvrapi.so
   • RemoveVrApiPatch — delete the game's libvrapi.so
   • CopyLibrariesPatch — copy in the rest of the bundle

2. The translation libraries (closed, NOT in the repo). The libraries it injects are downloaded at patch time from the author's server (ovrp.crx.moe/api/v1/releases/index -> files.crx.moe/.../libraries.zip), version- managed separately. Source unpublished.

What's actually in libraries.zip (black-box surface inspection)

The bundle is Meta's / vendors' proprietary binaries, not original code:

File	What it is
libOVRPlugin.so (4.1 MB, 611 ovrp_ exports)	Meta's own OVRPlugin — internal build paths intact in .rodata (arvr/projects/integrations/OVRPlugin/Src/Util/CompositorOpenXR.cpp). A newer build than RE4VR's bundled one (986 KB, VrApi-era), specifically one with the OpenXR compositor backend.
libopenxr_loader_{meta,pico,yvr,generic}.so	Per-vendor OpenXR loaders; the patcher picks one for the target headset.
libovrplatformloader*.so, libpxrplatformloader.so	Entitlement/platform loaders (the Frida-mocked entitlement piece).

Overport's actual strategy (now unambiguous)

For a VrApi-era title it: replaces the game's old VrApi-routed Meta OVRPlugin with a newer Meta OVRPlugin that has an OpenXR backend, deletes libvrapi.so, drops in the target vendor's OpenXR loader, and bypasses entitlement with Frida. The newer Meta OVRPlugin's CompositorOpenXR path then talks to e.g. Pico's OpenXR runtime.

Consequences:

• It ships Meta's (and Pico's/YVR's) proprietary binaries verbatim. That is a very different — and far more exposed — legal posture than a clean-room reimplementation.
• It depends on the newer OVRPlugin's C ABI still matching what the old game's UE/Unity build calls. For an old VrApi-era UE4 title like RE4VR this is not guaranteed; the surface has drifted across OVRPlugin versions.
• There is no original translation code to learn from — the hard part is Meta's, and we already have RE4VR's real libOVRPlugin_real.so for reference.

Why this matters for us

Our shim is the open, clean-room alternative to the one piece Overport keeps closed (and which is, in fact, Meta's). It can't be replaced by their blob in a clean open product because their blob is Meta's binary. Their patcher, however, is genuinely useful prior art for the packaging layer (entitlement strip, manifest/engine smali patches) — see the off-Quest patches we adopt below.

Quake III Arena VR Edition (GUNNM-VR/...)

A source port, not a shim. Built on the open-source Quake3e engine + baseq3a, recompiled for Android/Quest with Vulkan, using #ifdef to select OpenXR (PCVR) or VRAPI (Quest) at compile time. This is the easy case and the exact opposite of ours: with engine source you just compile against whichever runtime. We can't recompile RE4VR (closed UE4 binary), so we must be a binary-compatible libOVRPlugin.so instead. Useful only as a contrast.

Off-Quest patches worth adopting (packaging layer)

For RE4VR on a real Quest we need none of these — the shim alone is sufficient (good confirmation). They become necessary only when porting the APK to a non-Quest Android VR device (Pico / Steam Frame / Monado-on-Android). Reimplemented in our own packaging in packaging/steamframe_patches.sh (see the steamframe-port branch):

Patch (Overport name)	Why off-Quest	Status
OculusUnrealPatch	UE gates the Oculus HMD path on Build.MANUFACTURER/MODEL; off-Quest it's false so our shim is never called. Spoof them in GameActivity smali.	adopt
RemoveUsesLibraryPatch	Strip <uses-(native-)library> entries (except libopenxr.google.so) that name Meta-only libs and would block install/launch elsewhere.	adopt
DisableControllerOffsetPatch	Touch->other-controller pose offset; our xr_input has no offset, so non-Touch controllers may be misplaced.	shim TODO (runtime, not packaging)
RemoveUnrealForceQuitPatch	Strip System.exit from AndroidThunkJava_ForceQuit so a failed off-Quest check can't hard-kill the app.	adopt (defensive)
FixUnrealCrashPatch	Creates a stub UnityPlayer.currentActivity so an engine-agnostic injected blob can find the Activity.	skip — our shim gets the Activity natively from Initialize5 + JNI.
MetaXRAudioPatch	Hex-NOPs libMetaXRAudioWwise/Unity.so.	N/A — RE4VR uses libovraudio64.so, not Meta XR Audio.
DisableSpaceWarp / ForcePassthrough	Config toggles.	N/A — RE4VR doesn't use AppSpaceWarp; equivalent to our debug.re4vr.* props.

Sources

• Overport patcher: https://github.com/ovrport/app (GPLv3)
• Overport library index: https://ovrp.crx.moe/api/v1/releases/index
• Quake III VR Edition: https://github.com/GUNNM-VR/Quake-III-Arena-VR-Edition
• Meta deprecates VrApi / "all-in on OpenXR": https://developers.meta.com/horizon/blog/oculus-all-in-on-openxr-deprecates-proprietary-apis/
• OVRPlugin vs VRAPI vs LibOVR: https://developers.meta.com/horizon/documentation/unity/os-openxr-vrapi/
• Allegations Meta's OVRPlugin blocks non-Meta runtimes (Voices of VR #1526): https://voicesofvr.com/1526-allegations-that-metas-ovrplugin-is-undermining-the-spirit-of-openxr-by-blocking-non-meta-headsets-on-pcvr/