docs: def textwidth(self, text, config):
          """Calculates the width of the specified text.
          """
          surface = cairo.SVGSurface(None, 1280, 200)
          ctx = cairo.Context(surface)
          ctx.select_font_face(config['font_face'],
                               cairo.FONT_SLANT_NORMAL,
                               cairo.FONT_WEIGHT_BOLD)
          ctx.set_font_size(int(config['font_size']))
          return ctx.text_extents(text)[2] + 2