How to get a printer property value in render filter in Win7?

Question

I'm developing a v4 printer driver and I added a custom PRINTER_PROPERTY to my gpd file as follows:

*Feature: Pdl
{
    *Name: "Printer Definition Language"
    *FeatureType: PRINTER_PROPERTY
    *PrintSchemaKeywordMap: "Pdl"
    *DefaultOption: ps
    *Option: ps
    {
        *Name:  "Postscript"
    }
    *Option: pcl
    {
        *Name:  "PCL"
    }
}

I'm able to read its value in win 8 using IPrinterPropertyBag interface, but what should I do in win 7?

Piece of code which works in Win8:

VARIANT qPropBag;
if (SUCCEEDED(m_pIPropertyBag->GetProperty(XPS_FP_QUEUE_PROPERTY_BAG, &qPropBag)))
{
    auto pdisp = (IDispatch*)qPropBag.ppdispVal;
    IPrinterPropertyBag * pBag;
    if (SUCCEEDED(pdisp->QueryInterface<IPrinterPropertyBag>(&pBag)))
    {
        BSTR val;
        if (SUCCEEDED(pBag->GetString(L"Config:Pdl", &val))) {
            sFormat = val;
        }

        pBag->Release();
    }
}

Answer 1

I found it by myself (and a help of MS guys ) and here is the code:

VARIANT helper;
if (SUCCEEDED(m_pIPropertyBag->GetProperty(L"IPrintCoreHelper", &helper))) {

    IPrintCoreHelper * m_pCoreHelper;
    if (SUCCEEDED(V_UNKNOWN(&helper)->QueryInterface(IID_IPrintCoreHelper, reinterpret_cast<VOID**>(&m_pCoreHelper)))) {
        PCSTR val;
        if (SUCCEEDED(m_pCoreHelper->GetOption(NULL, 0, "Pdl", &val)))
            strcpy(sFormat, val); // usage

        m_pCoreHelper->Release();
    }
}
VariantClear(&helper);