Overriden shouldRelayout doesn't have access to BoxyDelegate about boxy

[pingbird]

Apologies if the docs are insufficient but the shouldRelayout and shouldRepaint methods are used in the same manner as CustomPainer.shouldRepaint, to compare custom properties that you have added to the constructor of the delegate:

class _TreeViewBoxy extends BoxyDelegate {
  _TreeViewBoxy({
    required this.root,
    required this.verticalSpacing,
    required this.horizontalSpacing,
  });

  ...

  @override
  bool shouldRelayout(_TreeViewBoxy oldDelegate) =>
      root != oldDelegate.root ||
          verticalSpacing != oldDelegate.verticalSpacing ||
          horizontalSpacing != oldDelegate.horizontalSpacing;
}

If your delegate has no parameters then there is no reason to implement the method.

If you want your boxy to relayout based on something other than it's own properties changing or constraints changing or a child updating, you'll probably need to use a notifier of some sort.

[WasserEsser]

Ah, I see, that makes sense. Thanks for clarifying!

[pingbird]

if the children are updated in any way the boxy will be laid out automatically, the error you are getting is from accessing the old delegate's children from outside of its lifecycle

[WasserEsser]

It sounds like I don't need to override the shouldRelayout function at all then.

But I don't understand how the error message is correct because all I'm doing is overriding the method (which, according to the error message should be the correct way). It's also already throwing an exception just accessing the boxy's current children, before trying to access the old delegate's children. It appears as though the shouldRelayout function (which I'm not calling myself) is being called outside of the boxy's lifecycle? Is that an error on my part? Because I don't see how I could influence this in any way. If not, it appears as though you just can't access any property of the boxy delegate or the old delegate in the shouldRelayout function, which makes the whole function pointless to override.