anchor.diff:  
   let
     inherit (lib)
  -    boolEn
  +    boolYn
       optionals;
   
     sources = {
  
positive.code:   };
  
    nativeBuildInputs = [
      python3
      yasm
    ];
  
    buildInputs = [
  
negative.code:     wayland
    ];
  
    mesonFlags = [
      "-Dwith_encoders=yes"
      "-Dwith_drm=${boolYn (libdrm != null)}"
      "-Dwith_x11=${boolYn (libx11 != null)}"
      "-Dwith_glx=${boolYn opengl-dummy.glx}"
      "-Dwith_wayland=${boolYn (opengl-dummy.egl && wayland != null)}"
      "-Dwith_egl=${boolYn opengl-dummy.egl}"
    ];
  
    postInstall = "rm -rvf $out/share/gtk-doc";
  