toString method
A string representation of this object.
Some classes have a default textual representation,
often paired with a static parse function (like int.parse).
These classes will provide the textual representation as
their string representation.
Other classes have no meaningful textual representation
that a program will care about.
Such classes will typically override toString to provide
useful information when inspecting the object,
mainly for debugging or logging.
Implementation
@override
String toString() => (ToString(runtimeType)
      ..add('direction', direction)
      ..add('textDirection', textDirection)
      ..add('verticalDirection', verticalDirection))
    .toString();