// main_grid
tgrid* main_grid = dynamic_cast<tgrid*>(pref_node.find("pref_main_grid", true));

// THIS WORKS
tlabel& value_label = find_widget<tlabel>(main_grid, "value", false);

// NEXT USECASE
setup_single_toggle("value_toggle"
        , preferences::get(option["field"], option["default"].to_bool())
        , boost::bind(set_ptr, option["field"].str(), _1)
        , main_grid);

// DEFINITION OF ABOVE
template <typename T>
void tpreferences::setup_single_toggle(
          const std::string& widget_id
        , const bool start_value
        , boost::function<void(bool)> callback
        , T& window)
{
    ttoggle_button& widget =
        find_widget<ttoggle_button>(&window, widget_id, false);

    widget.set_value(start_value);

    connect_signal_mouse_left_click(widget, boost::bind(
          &tpreferences::single_toggle_callback<T>
        , this, widget_id
        , callback, boost::ref(window)));
}

// ERROR
C:\Users\\Documents\wesnoth-git\src\gui\dialogs\preferences_dialog.cpp|165|error: no matching function for call to 'find_widget(gui2::tgrid**, const string&, bool)'|