--?   print(eq(old_top, pane.screen_top1), eq(old_top, {line=1, pos=1}), pane.top, cursor_sy, cursor_sy - Display_settings.y, App.screen.height - Header_height - Line_height)

--?     print(('screen top changed from (%d,%d) to (%d,%d)'):format(old_top.line, old_top.pos, pane.screen_top1.line, pane.screen_top1.pos))
--?     print('updating viewport based on screen top')
--?     print('from', Display_settings.y, y_of_schema1(pane, pane.screen_top1))

--?     print('to', Display_settings.y)