function test_up_arrow_skips_drawing()
  -- some lines of text with a drawing intermixed
  local drawing_width = 50
  App.screen.init{width=Editor_state.left+drawing_width, height=100}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc',               -- height 15
                                  '```lines', '```',   -- height 25
                                  'ghi'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=3, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'baseline/screen:1')
  y = y + Editor_state.line_height
  local drawing_height = Drawing_padding_height + drawing_width/2  -- default
  y = y + drawing_height
  App.screen.check(y, 'ghi', 'baseline/screen:3')
  check(Editor_state.cursor_x, 'baseline/cursor_x')
  -- after hitting the up arrow the cursor moves up by 2 lines, skipping the drawing
  edit.run_after_keychord(Editor_state, 'up')
  check_eq(Editor_state.cursor1.line, 1, 'cursor')
end
function test_up_arrow_scrolls_up_by_one_line()
end
function test_down_arrow_skips_drawing()
  -- some lines of text with a drawing intermixed
  local drawing_width = 50
  App.screen.init{width=Editor_state.left+drawing_width, height=100}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abc',               -- height 15
                                  '```lines', '```',   -- height 25
                                  'ghi'}
  Text.redraw_all(Editor_state)
  Editor_state.cursor1 = {line=1, pos=1}
  Editor_state.screen_top1 = {line=1, pos=1}
  Editor_state.screen_bottom1 = {}
  edit.draw(Editor_state)
  local y = Editor_state.top
  App.screen.check(y, 'abc', 'baseline/screen:1')
  y = y + Editor_state.line_height
  local drawing_height = Drawing_padding_height + drawing_width/2  -- default
  y = y + drawing_height
  App.screen.check(y, 'ghi', 'baseline/screen:3')
  check(Editor_state.cursor_x, 'baseline/cursor_x')
  -- after hitting the down arrow the cursor moves down by 2 lines, skipping the drawing
  edit.run_after_keychord(Editor_state, 'down')
  check_eq(Editor_state.cursor1.line, 3, 'cursor')
end
function test_down_arrow_scrolls_down_by_one_line()

        State.cursor1 = {line=new_cursor_line, posB=nil}
        Text.populate_screen_line_starting_pos(State, State.cursor1.line)
        local prev_line_cache = State.line_cache[State.cursor1.line]
        local prev_screen_line_starting_pos = prev_line_cache.screen_line_starting_pos[#prev_line_cache.screen_line_starting_pos]
        local prev_screen_line_starting_byte_offset = Text.offset(State.lines[State.cursor1.line].data, prev_screen_line_starting_pos)
        local s = string.sub(State.lines[State.cursor1.line].data, prev_screen_line_starting_byte_offset)
        State.cursor1.pos = prev_screen_line_starting_pos + Text.nearest_cursor_pos(s, State.cursor_x, State.left) - 1
        break
      end
        State.cursor1 = {line=new_cursor_line, pos=nil}
        Text.populate_screen_line_starting_pos(State, State.cursor1.line)
        -- previous text line found, pick its final screen line
--?         print('has multiple screen lines')
        local screen_line_starting_pos = State.line_cache[State.cursor1.line].screen_line_starting_pos
--?         print(#screen_line_starting_pos)
        screen_line_starting_pos = screen_line_starting_pos[#screen_line_starting_pos]
        local screen_line_starting_byte_offset = Text.offset(State.lines[State.cursor1.line].data, screen_line_starting_pos)
        local s = string.sub(State.lines[State.cursor1.line].data, screen_line_starting_byte_offset)
        State.cursor1.pos = screen_line_starting_pos + Text.nearest_cursor_pos(s, State.cursor_x, State.left) - 1
        break
      end