private void page_right (int step = 1) {


            if ((- current_position) < ((grid.n_columns - 5.8)*130)) {

                pages.move (grid, current_position - 5*130*step, 0);

                current_position -= 5*130*step;

            }


        }
###########################################################################
    private void page_right (int step = 1) {

            if ((- current_position) < ((grid.n_columns - 5.8)*130)) {
                int val = 0;
                Timeout.add (20, () => {
                    if (val < 5*130) {
                        pages.move (grid, current_position - val, 0);
                        current_position -= val;
                        val += 2;
                        return true;
                    } else {
                        return false;
                    }
                });
            }

        }