Display_settings.y = sy_of_screen_top_in_cursor_pane() - Margin_top  -- don't hide under column headers

    Display_settings.y = up_edge_sy(Cursor_pane.col, Cursor_pane.row) + y_of_schema1(pane, pane.screen_top1)
    Display_settings.y = Display_settings.y - Margin_top  -- don't hide under column headers

-- y coordinate of screen_top if a pane is editable
function sy_of_screen_top_in_cursor_pane()
  local pane = Surface[Cursor_pane.col][Cursor_pane.row]
  local result = up_edge_sy(Cursor_pane.col, Cursor_pane.row)
--?   print(('updating viewport y; cursor pane starts at %d; screen top is at %d,%d'):format(result, pane.screen_top1.line, pane.screen_top1.pos))
  if pane.screen_top1.line == 1 and pane.screen_top1.pos == 1 then

-- y offset of a given (line, pos)
function y_of_schema1(pane, loc)
  local result = 0
--?   print(('updating viewport y; cursor pane starts at %d; screen top is at %d,%d'):format(result, loc.line, loc.pos))
  if loc.line == 1 and loc.pos == 1 then

  for i=1,pane.screen_top1.line-1 do

  for i=1,loc.line-1 do

function screen_top_of_y_in_cursor_pane()

-- return (line, pos) of the screen line starting at or just below a
-- given a y offset
function schema1_of_y(pane, y)