FlowDelegate delegate

The delegate that controls the transformation matrices of the children.

Source 

FlowDelegate get delegate => _delegate;
void delegate=(FlowDelegate newDelegate)

When the delegate is changed to a new delegate with the same runtimeType as the old delegate, this object will call the delegate's FlowDelegate.shouldRelayout and FlowDelegate.shouldRepaint functions to determine whether the new delegate requires this object to update its layout or painting.

Source 

set delegate (FlowDelegate newDelegate) {
  assert(newDelegate != null);
  if (_delegate == newDelegate)
    return;
  final FlowDelegate oldDelegate = _delegate;
  _delegate = newDelegate;

  if (newDelegate.runtimeType != oldDelegate.runtimeType || newDelegate.shouldRelayout(oldDelegate))
    markNeedsLayout();
  else if (newDelegate.shouldRepaint(oldDelegate))
    markNeedsPaint();

  if (attached) {
    oldDelegate._repaint?.removeListener(markNeedsPaint);
    newDelegate._repaint?.addListener(markNeedsPaint);
  }
}