Lazily load StubLluiPlugin

This removes warning about StubLluiPlugin being not found, when it wouldn't be anyhow usefull

Author: mcpiroman

scripts/DllManipulatorScript.cs

@@ -48,6 +48,9 @@ private void OnEnable()
             DontDestroyOnLoad(gameObject);
 
             var timer = System.Diagnostics.Stopwatch.StartNew();
+
+            LowLevelPluginManager.ResetStubPlugin();
+
             DllManipulator.SetUnityContext(Thread.CurrentThread.ManagedThreadId, Application.dataPath);
             DllManipulator.Options = Options;
 
@@ -75,8 +78,6 @@ private void OnEnable()
                 }
             }
 
-            LowLevelPluginManager.Initialize();
-
             if (DllManipulator.Options.loadingMode == DllLoadingMode.Preload)
                 DllManipulator.LoadAll();
 
@@ -94,7 +95,7 @@ private void OnDestroy()
 
                 DllManipulator.UnloadAll();
                 DllManipulator.ForgetAllDlls();
-                DllManipulator.ClearCrashLogs();
+                DllManipulator.ClearCrashLogs();         
             }
         }
     }

scripts/LowLevelPluginManager.cs

@@ -12,39 +12,51 @@
 namespace UnityNativeTool.Internal
 {
     [DisableMocking]
-    class LowLevelPluginManager
+    static class LowLevelPluginManager
     {
+        private static bool _triedLoadingStubPlugin = false;
         private static IntPtr _unityInterfacePtr = IntPtr.Zero;
-        public static void Initialize()
-        {
-            try
-            {
-                _unityInterfacePtr = GetUnityInterfacesPtr();
-                if (_unityInterfacePtr == IntPtr.Zero)
-                    throw new Exception($"{nameof(GetUnityInterfacesPtr)} returned null");
-            }
-            catch(DllNotFoundException)
-            {
-                Debug.LogWarning("StubLluiPlugin not found. UnityPluginLoad and UnityPluginUnload callbacks won't fire. You may comment out this warning if you don't care about these callbacks.");
-            }
-        }
 
         public static void OnDllLoaded(NativeDll dll)
         {
-            if (_unityInterfacePtr == IntPtr.Zero)
-                return;
+            if (_triedLoadingStubPlugin && _unityInterfacePtr == IntPtr.Zero)
+               return;
 
             var unityPluginLoadFunc = new NativeFunction("UnityPluginLoad", dll) {
                 delegateType = typeof(UnityPluginLoadDel)
             };
 
             DllManipulator.LoadTargetFunction(unityPluginLoadFunc, true);
-            if (unityPluginLoadFunc.@delegate != null)
+            if (unityPluginLoadFunc.@delegate == null)
+                return;
+
+            if (!_triedLoadingStubPlugin)
+            {
+                try
+                {
+                    _unityInterfacePtr = GetUnityInterfacesPtr();
+                    if (_unityInterfacePtr == IntPtr.Zero)
+                        throw new Exception($"{nameof(GetUnityInterfacesPtr)} returned null");
+                }
+                catch (DllNotFoundException)
+                {
+                    Debug.LogWarning("StubLluiPlugin not found. UnityPluginLoad and UnityPluginUnload callbacks won't fire. If you didn't install UnityNativeTool from .unitypackage or it didn't contain the compiled plugin, you'll need to compile it manually. Alternatively, you may comment out this warning if you don't care about these callbacks.");
+                }
+                finally
+                {
+                    _triedLoadingStubPlugin = true;
+                }
+            }
+
+            if (_unityInterfacePtr != IntPtr.Zero)
                 ((UnityPluginLoadDel)unityPluginLoadFunc.@delegate)(_unityInterfacePtr);
         }
 
         public static void OnBeforeDllUnload(NativeDll dll)
         {
+            if (_unityInterfacePtr == IntPtr.Zero)
+                return;
+
             var unityPluginUnloadFunc = new NativeFunction("UnityPluginUnload", dll) {
                 delegateType = typeof(UnityPluginUnloadDel)
             };
@@ -53,6 +65,12 @@ public static void OnBeforeDllUnload(NativeDll dll)
             if (unityPluginUnloadFunc.@delegate != null)
                 ((UnityPluginUnloadDel)unityPluginUnloadFunc.@delegate)();
         }
+        
+        public static void ResetStubPlugin()
+        {
+            _triedLoadingStubPlugin = false;
+            _unityInterfacePtr = IntPtr.Zero;
+        }
 
         delegate void UnityPluginLoadDel(IntPtr unityInterfaces);
         delegate void UnityPluginUnloadDel();