How do I call functions that receive floating point values using IDispatch.Invoke?

Question

I\'m having trouble calling a function that has a floating point argument and a floating point result, using IDispatch.Invoke.

Here\'s a minimal reproductio

Answer 1

Well, that was a head-scratcher. The documentation for this "method" is very misleading, it is not a method. It behaves more like an indexed property and requires the DISPATCH_METHOD | DISPATCH_PROPERTYGET flags. CComPtr doesn't support that, you'll need to spin this by hand. This code worked:

    CComVariant result;
    CComVariant centimeters((float)2.0);
    DISPID dispid;
    LPOLESTR name = L"CentimetersToPoints";
    HRESULT hr = wordapp->GetIDsOfNames(IID_NULL, &name, 1, LOCALE_USER_DEFAULT, &dispid);
    assert(SUCCEEDED(hr));

    DISPPARAMS dispparams = { &centimeters, NULL, 1, 0};
    hr = wordapp->Invoke(dispid, IID_NULL, LOCALE_USER_DEFAULT,
            DISPATCH_METHOD | DISPATCH_PROPERTYGET, &dispparams, &result, nullptr, nullptr);
    assert(SUCCEEDED(hr));