Cursor_pos = Text.nearest_cursor_pos(Lines[Cursor_line].data, old_x)

          if Lines[Cursor_line].screen_line_starting_pos == nil then
            Cursor_pos = Text.nearest_cursor_pos(Lines[Cursor_line].data, old_x)
            break
          end
          local screen_line_starting_pos = Lines[Cursor_line].screen_line_starting_pos
          screen_line_starting_pos = screen_line_starting_pos[#screen_line_starting_pos]
          Top_screen_line_starting_pos = screen_line_starting_pos
          local s = string.sub(Lines[Cursor_line].data, screen_line_starting_pos)
          Cursor_pos = screen_line_starting_pos + Text.nearest_cursor_pos(s, old_x) - 1

    if previous line (above top of screen) wrapped, it scrolls up by only one screen line