Hi,

There appears to be a problem with marshalling a specific usage of a
System.Drawing.Color reference parameter from an unmanaged caller.

I have a .NET control exposing an interface as (managed C++):

public __gc __interface IManagedUIElement
   {
   void ElemBackColor([Out] System::Drawing::Color color)
   ...
   }

__sealed __gc class MyControl
   public System::Windows::Forms::UserControl,
   public IManagedUIElement
   {
   ...
   }

My control is calling a native dll (passing a pointer to it's CCW). The
native code then requests the IManagedUIElement interface and calls the
method ElemBackColor.

The COM equivalent interface is (IDL):

   interface IManagedUIElement : IUnknown {
   HRESULT ElemBackColor([out] OLE_COLOR* color);
   ...
   }

and the native code calls with:

         OLE_COLOR color;
         mp->ElemBackColor(&color);

This doesn't work (in fact Visual Studio hangs when stepping in within
the debugger and has to be killed with the Task Manager) as it appears
that the CCW marshaller isn't correctly handling the method parameter.

According to MSDN, the marshaller marshals System.Drawing.Color to
OLE_COLOR as one of a number of special cases. I have verified that this
marshalling happens correctly for all managed to unmanaged calls and for
[in] parameters of unmanaged to managed calls. The case that appears to
be broken is [out] parameters (and by extension [out,retval] parameters
and property gets).

It is also possible that the Type Library Exporter doesn't know about
this special case as the exported type library doesn't mention OLE_COLOR
at all - I had to roll my own IDL.

Here's hoping anyone can help me out with a workaround or confirmation.

Thanks,