Callback from OnRenderEvent?

Unity Engine
1

Comrades, tell me what’s the matter. There is a code like this:

Side - Unity (c#)

public class TestClass : MonoBehaviour
{
[UnmanagedFunctionPointer(CallingConvention.StdCall)]
delegate bool Delegate_InitializeNativeDLL(IntPtr ptr);

[UnmanagedFunctionPointer(CallingConvention.StdCall)]
delegate IntPtr Delegate_GetRenderEvent();

static InitializeNativeDLL _InitializeCore;

static GetRenderEvent _GetRenderEvent;


static private IntPtr pointerDll   = IntPtr.Zero;

private void Start()
{
............
skipped loading library with (LoadLibrary)
............
               IntPtr func;
               func = GetProcAddress(pointerDll, "InitializeNativeDLL");
               if (func != null)
                   _InitializeNativeDLL= Marshal.GetDelegateForFunctionPointer<Delegate_InitializeNativeDLL>(func);

               func = GetProcAddress(pointerDll, "GetRenderEventFunc");
               if (func  != null)
                   _GetRenderEvent = Marshal.GetDelegateForFunctionPointer<Delegate_GetRenderEvent>(func);

_InitializeNativeDLL(  Marshal.GetFunctionPointerForDelegate<Delegate_GetRenderEvent>(_Callback_FromNative))


// Run function!!!!!!!!!!
update_func(1);
}

static void _Callback_FromNative(IntPtr data)
{
         Debug.Log("Run UnityFunc from native side");
}


static public void update_func(int mode)
{
         GL.IssuePluginEvent(_GetRenderEvent(), mode);
}

private void OnDestroy()
{
           FreeLibrary(pointerDll);
}

Side - Native (C++)

typedef void (*_v_function_pv)(void*);

_v_function_pv _callbackTest = nullptr;

extern "C"
{
   UNITY_INTERFACE_EXPORT bool InitializeNativeDLL(void* _Callback_In)
   {
       _callbackTest = (_v_function_pv)_Callback_In;
       return true;
   }

// Plugin function to handle a specific rendering event
static void UNITY_INTERFACE_API OnRenderEvent(int eventID)
{
 _callbackTest (nullptr);
}

// Freely defined function to pass a callback to plugin-specific scripts
extern "C" UnityRenderingEvent UNITY_INTERFACE_EXPORT UNITY_INTERFACE_API
GetRenderEventFunc()
{
   return OnRenderEvent;
}

At the first start (Start) everything goes fine. DebugLog gives “Run UnityFunc from native side”. But when you want to re-launch (click on play) the editor freezes. You have to force it to terminate and restart Unity.

But, if I remove this line from the native side

// Plugin function to handle a specific rendering event
static void UNITY_INTERFACE_API OnRenderEvent (int eventID)
{
  // _callbackTest (nullptr);
}

then everything works fine, nothing crashes.
Even if you run _callbackTest (nullptr) with the InitializeNativeDLL function. Everything is OK. But it is worth moving to OnRenderEvent (int eventID) problems begin. Although the first launch goes well.

2

I’ve never used the UnmanagedFunctionPointerAttribute with Unity so I don’t have experience with it.

Have you tried doing the interop with the native plugin system, i.e, the DLLImportAttribute?

Here’s how I do it for my native C games in KurtMaster2D:

Once I got the signatures and ownership of memory correct, it works on Windows, Mac, iOS and Android flawlessly.

3

Thanks:), I will try to implement it through DLLImportAttribute.

4

Here’s also one more interop linkage thing I saw posted recently by user @Zer0Cool :

It might prove handy in your integrations, not sure. It is to call C# functions directly from C++, and again I caveat that I did not believe you could do that until reading the above, and personally I have not tried it myself, so YMMV.