local infile = App.open_for_reading(filename)

  local infile = App.open_for_reading(App.save_dir..filename)
  if not infile then
    infile = App.open_for_reading(App.source_dir..filename)
  end

-- the source editor supports only files in the save dir, not even subdirectories

-- the source editor supports only files in the save dir backed by the source dir

  if not infile then
    infile = App.open_for_reading(App.source_dir..State.filename)
  end