local cursor_sy = up_edge_sy(Cursor_pane.col, Cursor_pane.row) + y_of_schema1(pane, pane.cursor1)
--?   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)
  if not eq(old_top, pane.screen_top1) and eq(old_top, {line=1, pos=1}) and pane.top > Header_height and cursor_sy - Display_settings.y > App.screen.height - Header_height  - Line_height then
    -- pan the surface instead of scrolling within the pane
    pane.screen_top1 = old_top
    bring_cursor_of_cursor_pane_in_view('down')
    Surface.cursor_on_screen_check = true  -- cursor was on screen before keystroke, so it should remain on screen after
    return
  end

* select a pane that extends past bottom of viewport, hit ctrl+e, position cursor near bottom of pane, hit down arrow a few times. cursor continues to remain on screen, panning surface as necessary.

* select a pane that starts at or above top of and extends past bottom of viewport, hit ctrl+e, position cursor near bottom of pane, hit down arrow a few times. cursor continues to remain on screen, panning surface as necessary.
* select a pane that starts halfway down and extends past bottom of viewport, hit ctrl+e, position cursor near bottom of pane, hit down arrow a few times. cursor continues to remain on screen, panning surface as necessary.