Function is_empty

plugins/videobasedtracker/DirectShowCameraLib/WinVariant.h:263–265

/// @brief Determines if the variant passed is "empty"
template <typename T>
inline detail::enable_for_variants_t<T, bool> is_empty(T const &v) {
    return (v.vt == VT_EMPTY);
}

/// @overload
/// For wrapped variants. Also returns true if the wrapper itself is empty.