Editable_cursor_pane_updated_screen_top = not eq(old_top, pane.screen_top1)
    if Editable_cursor_pane_updated_screen_top then
--?       print('updating viewport based on screen top')
      Display_settings.y = up_edge_sy(Cursor_pane.col, Cursor_pane.row) + y_of_schema1(pane, pane.screen_top1)
--?       print(('display settings.y is now %d'):format(Display_settings.y))
      Surface.cursor_on_screen_check = true  -- cursor was on screen before keystroke, so it should remain on screen after
    end

    maybe_update_screen_top_of_cursor_pane(pane, old_top)

  end
end
function maybe_update_screen_top_of_cursor_pane(pane, old_top)
  Editable_cursor_pane_updated_screen_top = not eq(old_top, pane.screen_top1)
  if Editable_cursor_pane_updated_screen_top then
--?     print('updating viewport based on screen top')
    Display_settings.y = up_edge_sy(Cursor_pane.col, Cursor_pane.row) + y_of_schema1(pane, pane.screen_top1)
--?     print(('display settings.y is now %d'):format(Display_settings.y))
    Surface.cursor_on_screen_check = true  -- cursor was on screen before keystroke, so it should remain on screen after