# File lib_wpm/wpm.rb, line 1381
    def expand_string(key)
      if (@string_map.include? key) then
        properties = @string_map[key]
        widget = properties.create_widget

        text = ''
        widget.make_page do |page_text|
          text.concat(page_text)
        end

        return text
      end

      raise "not found a string widget of #{key.inspect}"
    end