anchor.diff:      glib
       libpng
       libspectre
  +    lzo
  +    opengl-dummy
  +    xorg.pixman
  +    zlib
  +  ]  ++ optionals opengl-dummy.glx [
       libx11
       libxcb
  -    lzo
  -    opengl-dummy
       xorg.libXext
       xorg.libXrender
  -    xorg.pixman
  -    zlib
     ];
   
     patches = [
  
positive.code:   inherit (lib)
      boolEn
      boolWt
      optionalString;
  in
  stdenv.mkDerivation rec {
  
negative.code:     "--disable-gallium"
      # Only one OpenGL backend may be selected at compile time
      # OpenGL X (gl), or OpenGL ES 2.0 (glesv2)
      "--${boolEn (!opengl-dummy.glesv2 && opengl-dummy.glx)}-gl"
      "--${boolEn opengl-dummy.glesv2}-glesv2"
      "--disable-cogl"  # recursive dependency
      # FIXME: fix directfb mirroring
  