Small threading fix, delay to main thread (#19)

* Small threading fix, delay to main thread

Previously when calling a function on a worker thread and encountering a load error, pausing would trigger a exception as we use the Unity API on a worker thread. 

This is only for Lazy mode, where the thread safety is not yet fully implemented.

* Extract DispatchOnMainThread

Author: rogerbarton

scripts/DllManipulator.cs

@@ -503,7 +503,7 @@ internal static void LoadTargetFunction(NativeFunction nativeFunction, bool igno
                     if (!ignoreLoadError)
                     {
                         dll.loadingError = true;
-                        Prop_EditorApplication_isPaused.Value?.SetValue(null, true);
+                        DispatchOnMainThread(() => { Prop_EditorApplication_isPaused.Value?.SetValue(null, true); });
                         throw new NativeDllException($"Could not load DLL \"{dll.name}\" at path \"{dll.path}\".");
                     }
 
@@ -529,7 +529,7 @@ internal static void LoadTargetFunction(NativeFunction nativeFunction, bool igno
                     if (!ignoreLoadError)
                     {
                         dll.symbolError = true;
-                        Prop_EditorApplication_isPaused.Value?.SetValue(null, true);
+                        DispatchOnMainThread(() => { Prop_EditorApplication_isPaused.Value?.SetValue(null, true); });
                         throw new NativeDllException($"Could not get address of symbol \"{nativeFunction.identity.symbol}\" in DLL \"{dll.name}\" at path \"{dll.path}\".");
                     }
 
@@ -568,6 +568,18 @@ private static void InvokeCustomTriggers(List<Tuple<MethodInfo, bool>> triggers,
                     methodInfo.Invoke(null, args);
             }
         }
+        
+        /// <summary>
+        /// Ensure the action is executed on the main thread. Executes immediately if on the main thread already,
+        /// otherwise the action is added to a queue <see cref="DllManipulatorScript.MainThreadTriggerQueue"/>
+        /// </summary>
+        private static void DispatchOnMainThread(Action action)
+        {
+            if(Thread.CurrentThread.ManagedThreadId == _unityMainThreadId)
+                action();
+            else
+                DllManipulatorScript.MainThreadTriggerQueue.Enqueue(action);
+        }
 
         /// <summary>
         /// Logs native function's call to file. If that file exists, it is overwritten. One file is maintained for each thread.