Initial public release: OVRPlugin→OpenXR interoperability shim

An independent reimplementation of Meta's libOVRPlugin ABI on top of OpenXR, so
VrApi-era Meta Quest VR titles can run on non-Meta OpenXR runtimes (Monado,
Steam Frame) instead of being locked to Meta hardware. Original code only — no
Meta/Epic/Capcom binaries, headers, or assets. Includes a desktop harness that
drives the shim against Monado headless.

Scope/legal: interoperability; entitlement handling is out of scope. See README
for the legal/scope section and docs/ for the research trail and design notes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01D6sFYGXZPsq3v7xtcDES6g

shim/build_host.sh

@@ -0,0 +1,54 @@
+#!/usr/bin/env bash
+# build_host.sh — desktop (x86_64 Linux) build of the shim + the OpenXR test harness.
+# Mirrors build_android.sh but targets the host so the OpenXR path can be driven against
+# Monado's simulated HMD on a PC (see tools/desktop-harness/). NOT the shipping artifact —
+# that's build_android.sh (arm64). Needs: a C compiler, libvulkan, and the OpenXR loader
+# (Debian: libvulkan-dev libopenxr-loader1 libopenxr-dev). Run tools/desktop-harness/run.sh
+# after this to launch it headless against monado-service.
+set -euo pipefail
+SHIM="$(cd "$(dirname "$0")" && pwd)"
+ROOT="$(cd "$SHIM/.." && pwd)"
+OUT="$ROOT/build/host"
+mkdir -p "$OUT"
+
+CC="${CC:-cc}"
+# _GNU_SOURCE: glibc gates dladdr/CLOCK_MONOTONIC behind it (the NDK exposes them by default).
+INC="-I$SHIM/include -I$SHIM/third_party/openxr -I$SHIM/third_party/vulkan"
+CFLAGS="-std=c11 -Wall -D_GNU_SOURCE -fPIC -O2 -g $INC"
+
+echo "== compiling shim sources (host) =="
+OBJS=()
+for f in "$SHIM"/src/*.c; do
+  o="$OUT/$(basename "${f%.c}").o"
+  "$CC" $CFLAGS -c "$f" -o "$o"
+  OBJS+=("$o")
+done
+
+# The shim's xr* calls resolve against the system OpenXR loader; Vulkan against libvulkan.
+# Detect the loader via ldconfig, falling back to a direct file probe (ldconfig reads
+# /etc/ld.so.cache, which some sandboxes block -> false negative).
+have_loader() {
+  ldconfig -p 2>/dev/null | grep -q libopenxr_loader && return 0
+  for d in /usr/lib /usr/lib/x86_64-linux-gnu /lib/x86_64-linux-gnu /usr/local/lib; do
+    [ -e "$d/libopenxr_loader.so" ] || [ -e "$d/libopenxr_loader.so.1" ] && return 0
+  done
+  return 1
+}
+if ! have_loader; then
+  echo "WARN: libopenxr_loader not found — install libopenxr-loader1 libopenxr-dev to link/run."
+  echo "      (objects built OK; skipping the .so + harness link.)"
+  exit 0
+fi
+
+echo "== linking libOVRPlugin.so (host) =="
+"$CC" -shared -o "$OUT/libOVRPlugin.so" "${OBJS[@]}" -lopenxr_loader -lvulkan -lpthread -ldl
+echo "built: $OUT/libOVRPlugin.so"
+
+echo "== building harness =="
+"$CC" -std=c11 -Wall -D_GNU_SOURCE -O2 -g -I"$SHIM/include" -I"$SHIM/third_party/vulkan" \
+   "$ROOT/tools/desktop-harness/harness.c" \
+   -o "$OUT/harness" \
+   -L"$OUT" -lOVRPlugin -lvulkan -lm -Wl,-rpath,"$OUT"
+echo "built: $OUT/harness"
+echo
+echo "run it headless against Monado:  tools/desktop-harness/run.sh"