anchor.diff:  , libsm
   , libx11
   , libxcomposite
  +, libxcursor
   , libxdamage
   , libxext
   , libxfixes
  +, libxi
   , libxinerama
   , libxkbcommon
   , libxrandr
  
positive.code: , channel
  }:
  
  assert libx11 != null ->
    xorg.libXcursor != null
    && xorg.libXi != null;
  
  let
    inherit (lib)
      boolEn
  
negative.code:     libsm
      libx11
      libxcomposite
      libxcursor
      libxdamage
      libxext
      libxfixes
      libxi
      libxinerama
      libxrandr
      libxrender
  