compute method

@override CSSValue? compute([ DOMContext? domContext ])

Implementation

@override
CSSValue? compute([DOMContext? domContext]) {
  var valA = CSSValue.from(a);
  if (valA == null) return null;
  var compA = CSSFunction.computeValue(valA);
  if (compA == null) return null;

  if (operation != null) {
    var valB = CSSValue.from(b!);
    if (valB == null) return null;
    var compB = CSSFunction.computeValue(valB);
    if (compB == null) return null;

    if (compA is CSSLength && compB is CSSLength) {
      if (compA.unit == compB.unit) {
        var val =
            computeCalcOperationSymbol(operation!, compA.value, compB.value);
        return CSSLength(val, compB.unit);
      } else {
        return null;
      }
    } else if (compA is CSSNumber && compB is CSSNumber) {
      var val =
          computeCalcOperationSymbol(operation!, compA.value!, compB.value!);
      return CSSNumber(val);
    } else {
      return null;
    }
  }

  return compA;
}