end
function test_select_text_repeatedly_using_mouse_and_shift()
  io.write('\ntest_select_text_repeatedly_using_mouse_and_shift')
  App.screen.init{width=50, height=60}
  Lines = load_array{'abc', 'def', 'xyz'}
  Line_width = App.screen.width
  Cursor1 = {line=1, pos=1}
  Screen_top1 = {line=1, pos=1}
  Screen_bottom1 = {}
  Selection1 = {}
  App.draw()  -- populate line.y for each line in Lines
  local screen_left_margin = 25  -- pixels
  -- click on first location
  App.run_after_mousepress(screen_left_margin+8,Margin_top+5, '1')
  App.run_after_mouserelease(screen_left_margin+8,Margin_top+5, '1')
  -- hold down shift and click on a second location
  App.keypress('lshift')
  App.run_after_mousepress(screen_left_margin+20,Margin_top+5, '1')
  App.run_after_mouserelease(screen_left_margin+20,Margin_top+Line_height+5, '1')
  -- hold down shift and click at a third location
  App.keypress('lshift')
  App.run_after_mousepress(screen_left_margin+20,Margin_top+5, '1')
  App.run_after_mouserelease(screen_left_margin+8,Margin_top+Line_height+5, '1')
  App.keyrelease('lshift')
  -- selection is between first and third location. forget the second location, not the first.
  check_eq(Selection1.line, 1, 'F - test_select_text_repeatedly_using_mouse_and_shift/selection:line')
  check_eq(Selection1.pos, 2, 'F - test_select_text_repeatedly_using_mouse_and_shift/selection:pos')
  check_eq(Cursor1.line, 2, 'F - test_select_text_repeatedly_using_mouse_and_shift/cursor:line')
  check_eq(Cursor1.pos, 2, 'F - test_select_text_repeatedly_using_mouse_and_shift/cursor:pos')

Old_cursor1, Old_selection1, Mousepress_shift = nil  -- some extra state to compute selection between mousepress and mouserelease

        if App.shift_down() then
          Selection1 = {line=Cursor1.line, pos=Cursor1.pos}
        end
        Cursor1 = {line=line_index, pos=Text.to_pos_on_line(line, x, y)}
        if not App.shift_down() then
          Selection1 = {line=Cursor1.line, pos=Cursor1.pos}
        end

        -- delicate dance between cursor, selection and old cursor
        -- manual tests:
        --  regular press+release: sets cursor, clears selection
        --  shift press+release:
        --    sets selection to old cursor if not set otherwise leaves it untouched
        --    sets cursor
        --  press and hold to start a selection: sets selection on press, cursor on release
        --  press and hold, then press shift: ignore shift
        --    i.e. mousereleased should never look at shift state
        Old_cursor1 = Cursor1
        Old_selection1 = Selection1
        Mousepress_shift = App.shift_down()
        Selection1 = {line=line_index, pos=Text.to_pos_on_line(line, x, y)}

          if Text.eq1(Cursor1, Selection1) and not App.shift_down() then
            Selection1 = {}

          if Mousepress_shift then
            if Old_selection1.line == nil then
              Selection1 = Old_cursor1
            else
              Selection1 = Old_selection1
            end

          Old_cursor1, Old_selection1, Mousepress_shift = nil