anchor.diff:      "--disable-gallium"
       # Only one OpenGL backend may be selected at compile time
       # OpenGL X (gl), or OpenGL ES 2.0 (glesv2)
  -    "--${boolEn (!gles2)}-gl"
  -    "--${boolEn gles2}-glesv2"
  -    "--disable-cogl" # recursive dependency
  +    "--${boolEn (!opengl-dummy.glexv2 && opengl-dummy.glx)}-gl"
  +    "--${boolEn opengl-dummy.glesv2}-glesv2"
  +    "--disable-cogl"  # recursive dependency
       # FIXME: fix directfb mirroring
       "--disable-directfb"
       "--disable-vg"
  -    "--${boolEn (mesa_noglu != null)}-egl"
  -    "--${boolEn (mesa_noglu != null)}-glx"
  -    "--disable-wgl"
  +    "--${boolEn (opengl-dummy.egl)}-egl"
  +    "--${boolEn (opengl-dummy.glx)}-glx"
  +    "--disable-wgl"  # Windows
       "--enable-script"
       "--enable-ft"
       "--enable-fc"
  
positive.code: let
    inherit (lib)
      boolEn
      optionalString;
  in
  stdenv.mkDerivation rec {
  
negative.code:     glib
      libpng
      libspectre
      libx11
      libxcb
      lzo
      opengl-dummy
      xorg.libXext
      xorg.libXrender
      xorg.pixman
  