code: function percentPx(parentWd, WD, noNeg) {
          var wd = WD || 0; // ensure it is number  // null --> 0
  
          if (wd >= 1 || wd == 0) return wd;else if (wd <= -1) return noNeg ? 0 : wd;else if (typeof parentWd != 'number') return null;else if (wd >= 0.9999) // 100%
            return parentWd;else if (wd >= 0) return wd * parentWd;else {
            if (noNeg) return 0;
            if (wd > -0.9999) return wd * parentWd;else return -parentWd; // -100%
          }
        }
docs: only for panel/unit/paragraph