[python-win32] win32com support for pointer in-parameters

[Jeremy Kloth]

I have been struggling with getting pointer parameters to work with the COM
interface for VirtualBox.  In particular, the IFramebuffer interface.  I
cannot seem to get the following to give the expected results:

interface IFramebuffer : IDispatch
{
    // snipped to just the interesting definition
    HRESULT RequestResize (
        [in] ULONG aScreenId,
        [in] ULONG aPixelFormat,
        [in] BYTE * aVRAM,
        [in] ULONG aBitsPerPixel,
        [in] ULONG aBytesPerLine,
        [in] ULONG aWidth,
        [in] ULONG aHeight,
        [out, retval] BOOL * aFinished
    );
};

The type for aVRAM ends up being (correctly) VT_BYREF | VT_UI1.
 Unfortunately PyIDispatch (incorrectly) converts the parameter to just
VT_UI1.  The offending code path is: PyGatewayBase::Invoke() ->
invoke_setup() -> PyCom_PyObjectFromVariant() -> VariantCopyInd().

My not so informed understanding is that pythoncom considers all VT_BYREF
parameters as out-type parameters whereas, in this case at least, it is not
always such.  Indeed, in this case, the aVRAM parameter needs to be the
*address* not the *value* for an object to implement IFramebuffer properly.

Note that the object implementing IFramebuffer is passed as argument to
another function much the same way as event listeners.

I believe the fix involves PyIDispatch somehow using the type information
to determine which parameters are not out-type and then to not dereference
those.

Any direction with this is greatly appreciated.

Jeremy Kloth
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