-- duplicate some logic from love.draw
    local top2 = Text.to2(Screen_top1)
--?     print(App.screen.height)
    local y = App.screen.height - math.floor(15*Zoom)
    while y >= 15 do
--?       print(y, top2.line)
      if Screen_top1.line == 1 and Screen_top1.pos == 1 then break end
      if Lines[Screen_top1.line].mode == 'text' then
        y = y - math.floor(15*Zoom)
      elseif Lines[Screen_top1.line].mode == 'drawing' then
        y = y - 20 - Drawing.pixels(Lines[Screen_top1.line].h)
      end
      top2 = Text.previous_screen_line(top2)
    end
    Screen_top1 = Text.to1(top2)
    Cursor1.line = Screen_top1.line
    Cursor1.pos = Screen_top1.pos
    Text.move_cursor_down_to_next_text_line_while_scrolling_again_if_necessary()
--?     print(Cursor1.line, Cursor1.pos, Screen_top1.line, Screen_top1.pos)

    Text.pageup()

    Screen_top1.line = Screen_bottom1.line
    Screen_top1.pos = Screen_bottom1.pos
--?     print('setting top to', Screen_top1.line, Screen_top1.pos)
    Cursor1.line = Screen_top1.line
    Cursor1.pos = Screen_top1.pos
    Text.move_cursor_down_to_next_text_line_while_scrolling_again_if_necessary()
--?     print('top now', Screen_top1.line)

    Text.pagedown()
  end
end
function Text.pageup()
  -- duplicate some logic from love.draw
  local top2 = Text.to2(Screen_top1)
--?   print(App.screen.height)
  local y = App.screen.height - math.floor(15*Zoom)
  while y >= 15 do
--?     print(y, top2.line)
    if Screen_top1.line == 1 and Screen_top1.pos == 1 then break end
    if Lines[Screen_top1.line].mode == 'text' then
      y = y - math.floor(15*Zoom)
    elseif Lines[Screen_top1.line].mode == 'drawing' then
      y = y - 20 - Drawing.pixels(Lines[Screen_top1.line].h)
    end
    top2 = Text.previous_screen_line(top2)

  Screen_top1 = Text.to1(top2)
  Cursor1.line = Screen_top1.line
  Cursor1.pos = Screen_top1.pos
  Text.move_cursor_down_to_next_text_line_while_scrolling_again_if_necessary()
--?   print(Cursor1.line, Cursor1.pos, Screen_top1.line, Screen_top1.pos)

function Text.pagedown()
  Screen_top1.line = Screen_bottom1.line
  Screen_top1.pos = Screen_bottom1.pos
--?   print('setting top to', Screen_top1.line, Screen_top1.pos)
  Cursor1.line = Screen_top1.line
  Cursor1.pos = Screen_top1.pos
  Text.move_cursor_down_to_next_text_line_while_scrolling_again_if_necessary()
--?   print('top now', Screen_top1.line)
end