function test_select_text_using_mouse_starting_below_text()
  -- I'd like to test what happens when a mouse click is below some page of
  -- text, potentially even in the middle of a line.
  -- However, it's brittle to set up a text line boundary just right.
  -- So I'm going to just check things below the bottom of the final line of
  -- text when it's in the middle of the screen.
  -- final screen line ends in the middle of screen
  App.screen.init{width=50, height=60}
  Editor_state = edit.initialize_test_state()
  Editor_state.lines = load_array{'abcde'}
  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, 'ab', 'baseline:screen:1')
  y = y + Editor_state.line_height
  App.screen.check(y, 'cde', 'baseline:screen:2')
  -- press mouse above first line of text
  edit.run_after_mouse_press(Editor_state, 5,App.screen.height-5, 1)
  -- selection is past bottom-most text in screen
  check(Editor_state.selection1.line ~= nil, 'selection:line-not-nil')
  check_eq(Editor_state.selection1.line, 1, 'selection:line')
  check_eq(Editor_state.selection1.pos, 6, 'selection:pos')
end

-- result: pos, index of screen line

function Text.pos_at_end_of_screen_line(State, loc1)
  Text.populate_screen_line_starting_pos(State, loc1.line)
  local line_cache = State.line_cache[loc1.line]
  local most_recent_final_pos = utf8.len(State.lines[loc1.line].data)+1
  for i=#line_cache.screen_line_starting_pos,1,-1 do
    local spos = line_cache.screen_line_starting_pos[i]
    if spos <= loc1.pos then
      return most_recent_final_pos
    end
    most_recent_final_pos = spos-1
  end
  assert(false)
end

-- inefficient for some reason, so don't do it on every frame

  local line,pos = Text.to_pos(State, App.mouse_x(), App.mouse_y())
  return line, pos
end
function Text.to_pos(State, x,y)

  local x,y = App.mouse_x(), App.mouse_y()

  return State.screen_bottom1.line, Text.pos_at_end_of_screen_line(State, State.screen_bottom1)

  local screen_bottom1 = {line=nil, pos=nil}

    State.screen_bottom1 = {line=line_index, pos=nil}

    screen_bottom1.line = line_index

      y, State.screen_bottom1.pos = Text.draw(State, line_index, y, startpos)

      y, screen_bottom1.pos = Text.draw(State, line_index, y, startpos)

  State.screen_bottom1 = screen_bottom1

  print_and_log(('edit.mouse_press: cursor at %d,%d'):format(State.cursor1.line, State.cursor1.pos))

--?   print_and_log(('edit.mouse_press: cursor at %d,%d'):format(State.cursor1.line, State.cursor1.pos))

        break

        return

        break

        return

  -- still here? click is below all screen lines
  State.old_cursor1 = State.cursor1
  State.old_selection1 = State.selection1
  State.mousepress_shift = App.shift_down()
  State.selection1 = {
      line=State.screen_bottom1.line,
      pos=Text.pos_at_end_of_screen_line(State, State.screen_bottom1),
  }

  print_and_log(('edit.mouse_release: cursor at %d,%d'):format(State.cursor1.line, State.cursor1.pos))

--?   print_and_log(('edit.mouse_release: cursor at %d,%d'):format(State.cursor1.line, State.cursor1.pos))

    print_and_log('edit.mouse_release: no current drawing')

--?     print_and_log('edit.mouse_release: no current drawing')

          print_and_log(('edit.mouse_release: in line %d'):format(line_index))

--?           print_and_log(('edit.mouse_release: in line %d'):format(line_index))

          print_and_log(('edit.mouse_release: cursor now %d,%d'):format(State.cursor1.line, State.cursor1.pos))

--?           print_and_log(('edit.mouse_release: cursor now %d,%d'):format(State.cursor1.line, State.cursor1.pos))

    print_and_log(('edit.mouse_release: finally selection %s,%s cursor %d,%d'):format(tostring(State.selection1.line), tostring(State.selection1.pos), State.cursor1.line, State.cursor1.pos))

--?     print_and_log(('edit.mouse_release: finally selection %s,%s cursor %d,%d'):format(tostring(State.selection1.line), tostring(State.selection1.pos), State.cursor1.line, State.cursor1.pos))