else
      assert(false)

  check_nil(p2.name, 'F - test_move_point/baseline/p2:name')

function test_move_point_on_manhattan_line()
  io.write('\ntest_move_point_on_manhattan_line')
  -- create a drawing with a manhattan line
  Filename = 'foo'
  App.screen.init{width=Margin_left+300, height=300}
  Lines = load_array{'```lines', '```', ''}
  Line_width = 256  -- drawing coordinates 1:1 with pixels
  Current_drawing_mode = 'manhattan'
  App.draw()
  App.run_after_mouse_press(Margin_left+5, Margin_top+Drawing_padding_top+6, 1)
  App.run_after_mouse_release(Margin_left+35, Margin_top+Drawing_padding_top+46, 1)
  local drawing = Lines[1]
  check_eq(#drawing.shapes, 1, 'F - test_move_point_on_manhattan_line/baseline/#shapes')
  check_eq(#drawing.points, 2, 'F - test_move_point_on_manhattan_line/baseline/#points')
  check_eq(drawing.shapes[1].mode, 'manhattan', 'F - test_move_point_on_manhattan_line/baseline/shape:1')
  App.draw()
  -- enter 'move' mode
  App.run_after_keychord('C-u')
  check_eq(Current_drawing_mode, 'move', 'F - test_move_point_on_manhattan_line/mode:1')
  -- move point
  App.mouse_move(Margin_left+26, Margin_top+Drawing_padding_top+44)
  App.update(0.05)
  -- line is no longer manhattan
  check_eq(drawing.shapes[1].mode, 'line', 'F - test_move_point_on_manhattan_line/baseline/shape:1')
end

        Drawing.relax_constraints(drawing, drawing.pending.target_point_index)

      if drawing.mode == 'manhattan' then
        drawing.mode = 'line'
      elseif drawing.mode == 'rectangle' or drawing.mode == 'square' then
        drawing.mode = 'polygon'
      end

      Drawing.relax_constraints(drawing, drawing.pending.target_point_index)

function Drawing.relax_constraints(drawing, p)
  for _,shape in ipairs(drawing.shapes) do
    if shape.mode == 'manhattan' then
      if shape.p1 == p then
        shape.mode = 'line'
      elseif shape.p2 == p then
        shape.mode = 'line'
      end
    elseif shape.mode == 'rectangle' or shape.mode == 'square' then
      for _,v in ipairs(shape.vertices) do
        if v == p then
          shape.mode = 'polygon'
        end
      end
    end
  end
end

    local drawing_index,drawing,_,p = Drawing.select_point_at_mouse()

    local drawing_index,drawing,i,p = Drawing.select_point_at_mouse()

      drawing.pending = {mode=Current_drawing_mode, target_point=p}

      drawing.pending = {mode=Current_drawing_mode, target_point=p, target_point_index=i}