sigc::signal<void, unsigned, const Row &> signal_row_added;
sigc::signal<void, unsigned, const Row &> signal_row_modified;
sigc::signal<void, unsigned> signal_row_removed;
sigc::signal<void, unsigned, const Row &> signal_row_added;
sigc::signal<void, unsigned, const Row &> signal_row_modified;
sigc::signal<void, unsigned> signal_row_removed;