def _scroll_up(self, cli):
        " Scroll window up. "
        info = self.render_info

        if info.vertical_scroll > 0:
            # TODO: not entirely correct yet in case of line wrapping and long lines.
            if info.cursor_position.y >= info.window_height - 1 - info.configured_scroll_offsets.bottom:
                self.content.move_cursor_up(cli)

            self.vertical_scroll -= 1
Scroll window up.