anchor.diff:  		(fullscreen nil)
   		(no-frame nil)
   		(alpha-size 8)
  -		(depth-size 32)
  -		(stencil-size 32)
  +		depth-size
  +		stencil-size
   		(red-size 8)
   		(green-size 8)
   		(blue-size 8)
  
positive.code: 
  		  (sdl2:gl-set-attr :context-profile-mask 1)
  		  (sdl2:gl-set-attr :alpha-size alpha-size)
  		  (sdl2:gl-set-attr :depth-size depth-size)
  		  (sdl2:gl-set-attr :stencil-size stencil-size)
  		  (sdl2:gl-set-attr :red-size red-size)
  		  (sdl2:gl-set-attr :green-size green-size)
  		  (sdl2:gl-set-attr :blue-size blue-size)
  
negative.code: 	       (fullscreen nil)
  	       (no-frame nil)
  	       (alpha-size 8)
  	       depth-size
  	       stencil-size
  	       (red-size 8)
  	       (green-size 8)
  	       (blue-size 8)
  