resolve method
- @override
override
    Convert this instance into an EdgeInsets, which uses literal coordinates
(i.e. the left coordinate being explicitly a distance from the left, and
the right coordinate being explicitly a distance from the right).
See also:
- EdgeInsets, for which this is a no-op (returns itself).
- EdgeInsetsDirectional, which flips the horizontal direction
based on the directionargument.
Implementation
@override
EdgeInsets resolve(TextDirection direction) {
  assert(direction != null);
  switch (direction) {
    case TextDirection.rtl:
      return EdgeInsets.fromLTRB(end, top, start, bottom);
    case TextDirection.ltr:
      return EdgeInsets.fromLTRB(start, top, end, bottom);
  }
  return null;
}