bool isUniform

Whether all four sides of the border are identical.

Source 

@override
bool get isUniform {
  assert(horizontalInside != null);
  assert(verticalInside != null);
  if (!super.isUniform)
    return false;

  final Color topColor = top.color;
  if (horizontalInside.color != topColor ||
      verticalInside.color != topColor)
    return false;

  final double topWidth = top.width;
  if (horizontalInside.width != topWidth ||
      verticalInside.width != topWidth)
    return false;

  final BorderStyle topStyle = top.style;
  if (horizontalInside.style != topStyle ||
      verticalInside.style != topStyle)
    return false;

  return true;
}