# File gtk/sample/gtk-demo/cairo-clip-rectangle.rb, line 19
    def draw(cr)
      cr.new_path
      cr.move_to(0.25, 0.25)
      cr.line_to(0.25, 0.75)
      cr.line_to(0.75, 0.75)
      cr.line_to(0.75, 0.25)
      cr.line_to(0.25, 0.25)
      cr.close_path
      
      cr.clip
      
      cr.move_to(0, 0)
      cr.line_to(1, 1)
      cr.stroke
    end