addHours method
Implementation
void addHours(int hours) {
final hr = ptr.ref.vtable
.elementAt(75)
.cast<Pointer<NativeFunction<HRESULT Function(Pointer, Int32 hours)>>>()
.value
.asFunction<int Function(Pointer, int hours)>()(ptr.ref.lpVtbl, hours);
if (FAILED(hr)) throw WindowsException(hr);
}