anchor.diff:  
         # other options
         backend = ${toJSON cfg.backend};
  -      vsync = ${lib.boolToString cfg.vSync};
  +      vsync = ${boolToString cfg.vSync};
         refresh-rate = ${toString cfg.refreshRate};
       '' + cfg.extraOptions);
   
  
positive.code: 
    cfg = config.services.compton;
  
    floatBetween = a: b: with lib; with types;
      addCheck str (x: versionAtLeast x a && versionOlder x b);
  
    pairOf = x: with types; addCheck (listOf x) (y: lib.length y == 2);
  
    opacityRules = optionalString (length cfg.opacityRules != 0)
      (concatMapStringsSep ",\n" (rule: ''"${rule}"'') cfg.opacityRules);
  
negative.code:       fade-in-step  = ${elemAt cfg.fadeSteps 0};
        fade-out-step = ${elemAt cfg.fadeSteps 1};
        fade-exclude  = ${toJSON cfg.fadeExclude};
      '' + optionalString cfg.shadow ''
  
        # shadows
        shadow = true;
  