-- This little bit of state ensures we don't mess with a pane's screen_top
  -- if it was just used to update the viewport.
  Editable_cursor_pane_updated_screen_top = false

          if should_update_screen_top(column_index, pane_index, pane) then
            if body_sy < Display_settings.y then
              pane.screen_top1, y_offset = schema1_of_y(pane, Display_settings.y - body_sy)
            else
              pane.screen_top1 = {line=1, pos=1}
            end

          if body_sy < Display_settings.y then
            pane.screen_top1, y_offset = schema1_of_y(pane, Display_settings.y - body_sy)
          else
            pane.screen_top1 = {line=1, pos=1}

function plan_draw_but_dont_clobber_screen_top_in_cursor_pane()

function plan_draw_maybe_updating_screen_top_in_cursor_pane(update_screen_top_in_cursor_pane)

          if should_update_screen_top(column_index, pane_index, pane, {ignore_editable_cursor_pane=true}) then

          if should_update_screen_top(column_index, pane_index, update_screen_top_in_cursor_pane) then

function should_update_screen_top(column_index, pane_index, pane, options)

function should_update_screen_top(column_index, pane_index, including_cursor_pane)

  -- update the cursor pane either if it's not editable, or
  -- if it was explicitly requested
  if not pane.editable then return true end
  if options == nil then return true end
  if not options.ignore_editable_cursor_pane then return true end
  if not Editable_cursor_pane_updated_screen_top then return true end
  return false

  return including_cursor_pane

            maybe_update_screen_top_of_cursor_pane(pane, old_top)

            local cursor_pane_updated_screen_top = maybe_update_screen_top_of_cursor_pane(pane, old_top)

            plan_draw_but_dont_clobber_screen_top_in_cursor_pane()

            plan_draw_maybe_updating_screen_top_in_cursor_pane(not cursor_pane_updated_screen_top)

  Editable_cursor_pane_updated_screen_top = not eq(old_top, pane.screen_top1)
  if Editable_cursor_pane_updated_screen_top then

  local update = not eq(old_top, pane.screen_top1)
  if update then

  return update