function test_click_on_wrapping_line()
  io.write('\ntest_click_on_wrapping_line')
  -- display a wrapping line
  App.screen.init{width=80, height=80}
                  --  12345678901234
  Lines = load_array{"madam I'm adam"}
  Line_width = 75
  Cursor1 = {line=1, pos=1}
  Screen_top1 = {line=1, pos=1}
  Screen_bottom1 = {}
  App.draw()
  local y = Margin_top
  App.screen.check(y, 'madam ', 'F - test_click_on_wrapping_line/baseline/screen:1')
  y = y + Line_height
  App.screen.check(y, "I'm ada", 'F - test_click_on_wrapping_line/baseline/screen:2')
  y = y + Line_height
  -- click past end of second screen line
  App.draw()
  App.run_after_mouse_click(App.screen.width-2,y-2, 1)
  -- cursor moves to end of screen line
  check_eq(Cursor1.line, 1, 'F - test_click_on_wrapping_line/cursor:line')
  check_eq(Cursor1.pos, 13, 'F - test_click_on_wrapping_line/cursor:pos')
end
function test_click_past_end_of_wrapping_line()
  io.write('\ntest_click_past_end_of_wrapping_line')
  -- display a wrapping line
  App.screen.init{width=80, height=80}
                  --  12345678901234
  Lines = load_array{"madam I'm adam"}
  Line_width = 75
  Cursor1 = {line=1, pos=1}
  Screen_top1 = {line=1, pos=1}
  Screen_bottom1 = {}
  App.draw()
  local y = Margin_top
  App.screen.check(y, 'madam ', 'F - test_click_past_end_of_wrapping_line/baseline/screen:1')
  y = y + Line_height
  App.screen.check(y, "I'm ada", 'F - test_click_past_end_of_wrapping_line/baseline/screen:2')
  y = y + Line_height
  App.screen.check(y, 'm', 'F - test_click_past_end_of_wrapping_line/baseline/screen:3')
  y = y + Line_height
  -- click past the end of it
  App.draw()
  App.run_after_mouse_click(App.screen.width-2,y-2, 1)
  -- cursor moves to end of line
  check_eq(Cursor1.pos, 15, 'F - test_click_past_end_of_wrapping_line/cursor')  -- one more than the number of UTF-8 code-points
end

        return line.screen_line_starting_pos[screen_line_index+1]

        return line.screen_line_starting_pos[screen_line_index+1]-1