# File gtk/sample/gtk-demo/cairo-text-align-center.rb, line 21
    def draw(cr)
      cr.select_font_face("Sans",
                          Cairo::FONT_SLANT_NORMAL,
                          Cairo::FONT_WEIGHT_NORMAL)
      
      cr.set_font_size(0.2)
      extents = cr.text_extents(TEXT)
      x = 0.5 - (extents.width / 2 + extents.x_bearing)
      y = 0.5 - (extents.height / 2 + extents.y_bearing)
      
      cr.move_to(x, y)
      cr.show_text(TEXT)
      
      # draw helping lines
      cr.set_source_rgba(1, 0.2, 0.2, 0.6)
      cr.arc(x, y, 0.05, 0, 2 * Math::PI)
      cr.fill
      cr.move_to(0.5, 0)
      cr.rel_line_to(0, 1)
      cr.move_to(0, 0.5)
      cr.rel_line_to(1, 0)
      cr.stroke
    end