MarshalDirectiveException when calling IContextCallback.ContextCallback on .NET 7

roboz0r commented 1 year ago

Actual behavior

Attempting to call IContextCallback.ContextCallback with the automatically generated function signature results in the exception:

System.Runtime.InteropServices.MarshalDirectiveException: 'Cannot marshal 'parameter #1': .NET Core does not support marshalling delegates to the _Delegate interface provided by the .NET Framework COM Type Library. To marshal a delegate as an interface, marshal it as an IDispatch pointer.'

Expected behavior

The call completes without error.

Repro steps

NativeMethods.txt content:
```
CoGetObjectContext
IContextCallback
```

NativeMethods.json content (if present):

{
"$schema": "https://aka.ms/CsWin32.schema.json",
"emitSingleFile": false,
"public": true,
"comInterop": {
"useIntPtrForComOutPointers": true
}
}

Any of your own code that should be shared?

I copied the generated interface code and added [MarshalAs(UnmanagedType.FunctionPtr)] to the parameter and it now seems to call successfully.

    [Guid("000001DA-0000-0000-C000-000000000046")]
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    [SupportedOSPlatform("windows5.0")]
    [GeneratedCode("Microsoft.Windows.CsWin32", "0.2.206-beta+27f494b7ea")]
    public interface IContextCallback
    {
        unsafe void ContextCallback(
          // PFNCONTEXTCALL pfnCallback,
          [MarshalAs(UnmanagedType.FunctionPtr)] PFNCONTEXTCALL pfnCallback,
          ComCallData* pParam,
          Guid* riid,
          int iMethod,
          object pUnk);
    }

Context

CsWin32 version: 0.2.206-beta
Win32Metadata version: 46.0.5-preview
Target Framework: net7.0-windows

AArnott commented 1 year ago

Thanks for the excellent bug report and for sharing the solution you found. I'll research it some and (likely) apply the fix you found to the generated code.

RibShark commented 3 months ago

The same bug seems to apply to IDirectDraw.EnumDisplayModes and the equivalents for the other DirectDraw versions, they need the MarshalAs attribute on the callback param.

microsoft / CsWin32