Polyfill LUA_RIDX_MAINTHREAD;

Instead of using a static variable.

src/api/headset.c

@@ -76,9 +76,8 @@ static HeadsetRenderData headsetRenderData;
 
 static void renderHelper(void* userdata) {
   HeadsetRenderData* renderData = userdata;
+  lua_State* L = renderData->L;
 #ifdef LOVR_HEADSET_HELPER_USES_REGISTRY
-  // Emscripten and Oculus Mobile path
-  lua_State* L = luax_getmainstate();
   lua_getglobal(L, "_lovrHeadsetRenderError");
   bool noError = lua_isnil(L, -1);
   lua_pop(L, 1);
@@ -91,9 +90,6 @@ static void renderHelper(void* userdata) {
     lua_pop(L, 1); // pop luax_getstack
   }
 #else
-  // Normal path
-  lua_State* L = renderData->L;
-  lua_pushvalue(L, -1);
   lua_call(L, 0, 0);
 #endif
 }
@@ -279,8 +275,12 @@ static int l_lovrHeadsetRenderTo(lua_State* L) {
   }
 
   headsetRenderData.ref = luaL_ref(L, LUA_REGISTRYINDEX);
-#endif
+  lua_rawgeti(L, LUA_REGISTRYINDEX, LUA_RIDX_MAINTHREAD);
+  headsetRenderData.L = lua_tothread(L, -1);
+  lua_pop(L, 1);
+#else
   headsetRenderData.L = L;
+#endif
   lovrHeadsetDriver->renderTo(renderHelper, &headsetRenderData);
   return 0;
 }

src/luax.c

@@ -301,12 +301,9 @@ int luax_pushLovrHeadsetRenderError(lua_State *L) {
   return haveRenderError;
 }
 
-static lua_State *luax_mainstate;
-
-lua_State *luax_getmainstate() {
-  return luax_mainstate;
-}
-
-void luax_setmainstate(lua_State *L) {
-  luax_mainstate = L;
+#if LUA_VERSION_NUM < 502
+void luax_setmainthread(lua_State *L) {
+  lua_pushthread(L);
+  lua_rawseti(L, LUA_REGISTRYINDEX, LUA_RIDX_MAINTHREAD);
 }
+#endif

src/luax.h

@@ -28,5 +28,10 @@ void luax_pushconf(lua_State* L);
 int luax_setconf(lua_State* L);
 Color luax_checkcolor(lua_State* L, int index);
 int luax_pushLovrHeadsetRenderError(lua_State *L);
-lua_State *luax_getmainstate(void);
-void luax_setmainstate(lua_State *L);
+
+#if LUA_VERSION_NUM < 502
+#define LUA_RIDX_MAINTHREAD 1
+void luax_setmainthread(lua_State* L);
+#else
+#define luax_setmainthread
+#endif

src/main.c

@@ -70,7 +70,7 @@ int main(int argc, char** argv) {
 
   do {
     lua_State* L = luaL_newstate();
-    luax_setmainstate(L);
+    luax_setmainthread(L);
     luaL_openlibs(L);
 
     lua_State* T = lovrInit(L, argc, argv);
@@ -92,7 +92,6 @@ int main(int argc, char** argv) {
     restart = lua_type(T, -1) == LUA_TSTRING && !strcmp(lua_tostring(T, -1), "restart");
     status = lua_tonumber(T, -1);
     lua_close(L);
-    luax_setmainstate(NULL);
 #endif
   } while (restart);