# File gtk/sample/gtk-demo/cairo-gradient.rb, line 19
    def draw(cr)
      pat = Cairo::LinearPattern.new(0.0, 0.0,  0.0, 1.0)
      pat.add_color_stop_rgb(1, 0, 0, 0)
      pat.add_color_stop_rgb(0, 1, 0, 0)
      cr.rectangle(0, 0, 1, 1)
      cr.set_source(pat)
      cr.fill
      
      pat = Cairo::RadialPattern.new(0.45, 0.4, 0.1, 0.4, 0.4, 0.5)
      pat.add_color_stop_rgba(0, 1, 1, 1, 0.8)
      pat.add_color_stop_rgba(1, 0, 0, 0)
      cr.set_source(pat)
      cr.arc(0.5, 0.5, 0.3, 0, 2 * Math::PI)
      cr.fill
    end