print('=>', Cursor_line, Cursor_pos, Screen_bottom_line)

      print('scroll up preserving cursor')

      print('screen top after:', Screen_top_line, Top_screen_line_starting_pos)

  local y = Screen_height - math.floor(15*Zoom) -- for Cursor_line

  local cursor_pos_screen_lines = Text.pos_at_start_of_cursor_screen_line()
  print('cursor pos '..tostring(Cursor_pos)..' is on the #'..tostring(cursor_pos_screen_lines)..' screen line down')
  local y = Screen_height - cursor_pos_screen_lines*math.floor(15*Zoom)
  -- duplicate some logic from love.draw

    y = y - math.floor(15*Zoom)
    if Lines[Screen_top_line].mode == 'drawing' then
      y = y - Drawing.pixels(Lines[Screen_top_line].h)

    print('y', y)
    local h = 0
    if Lines[Screen_top_line-1].mode == 'drawing' then
      h = 20 + Drawing.pixels(Lines[Screen_top_line-1].h)
    elseif Lines[Screen_top_line-1].screen_line_starting_pos == nil then
      h = h + math.floor(15*Zoom)  -- text height
    else
      local n = #Lines[Screen_top_line-1].screen_line_starting_pos
      h = h + n*math.floor(15*Zoom)  -- text height
    end
    print('height:', h)
    if y - h < 0 then
      break

    y = y - h