def pre_render
      @attr = @source.attr
      cp = get_color($datacolor, @source.color(), @source.bgcolor())
      @color_pair = @source.color_pair || cp
      @cp = FFI::NCurses.COLOR_PAIR(cp)
    end
def pre_render
      @attr = @source.attr
      cp = get_color($datacolor, @source.color(), @source.bgcolor())
      @color_pair = @source.color_pair || cp
      @cp = FFI::NCurses.COLOR_PAIR(cp)
    end
have the renderer get the latest colors from the widget.
 Override this if for some reason the renderer wishes to hardcode its own.
 But then the widgets colors would be changed ?