Throw custom Error/Exception when target position is not found

[juskek]

Hi there, great package!

I was wondering if it would be possible to add a feature which throws a custom Error/Exception when the target position is not found, so that it can be handled. E.g., when the widget is not shown in a specific UI flow, then the following is printed:

"TutorialCoachMark (ERROR): It was not possible to obtain target position."

I would like to catch this and show the tutorial again next time on a different flow, so I was wondering if the following would work in util.dart.

import 'package:flutter/widgets.dart';
import 'package:tutorial_coach_mark/src/target/target_focus.dart';
import 'package:tutorial_coach_mark/src/target/target_position.dart';

enum ShapeLightFocus { Circle, RRect }

TargetPosition? getTargetCurrent(TargetFocus target,
//!
    {bool throwNotFoundException = false}) {
  if (target.keyTarget != null) {
    var key = target.keyTarget!;

    try {
      final RenderBox renderBoxRed =
          key.currentContext!.findRenderObject() as RenderBox;
      final size = renderBoxRed.size;
      final state =
          key.currentContext!.findAncestorStateOfType<NavigatorState>();
      Offset offset;
      if (state != null) {
        offset = renderBoxRed.localToGlobal(Offset.zero,
            ancestor: state.context.findRenderObject());
      } else {
        offset = renderBoxRed.localToGlobal(Offset.zero);
      }

      return TargetPosition(size, offset);
    } catch (e) {
//!
      if (throwNotFoundException) {
        throw TargetNotFoundException(
            'TutorialCoachMark (ERROR): It was not possible to obtain target position.');
      } else {
        print(
            "TutorialCoachMark (ERROR): It was not possible to obtain target position.");
        return null;
      }
    }
  } else {
    return target.targetPosition;
  }
}

abstract class TutorialCoachMarkController {
  void next();
  void previous();
  void skip();
}

extension StateExt on State {
  void safeSetState(VoidCallback call) {
    if (mounted) {
      // ignore: invalid_use_of_protected_member
      setState(call);
    }
  }
}

//!
class TargetNotFoundException implements Exception {
  String message;
  TargetNotFoundException(this.message);
}