anchor.diff:  // found in the LICENSE file.
   
   import 'dart:ui' as ui;
  +import 'dart:ui' show PointerChange;
   
   import 'package:flutter/cupertino.dart';
   import 'package:flutter/foundation.dart';
  
positive.code: void main() {
    setUp(ensureTestGestureBinding);
  
    final List<PointerEnterEvent> enter = <PointerEnterEvent>[];
    final List<PointerHoverEvent> move = <PointerHoverEvent>[];
    final List<PointerExitEvent> exit = <PointerExitEvent>[];
    final MouseTrackerAnnotation annotation = MouseTrackerAnnotation(
      onEnter: (PointerEnterEvent event) => enter.add(event),
      onHover: (PointerHoverEvent event) => move.add(event),
      onExit: (PointerExitEvent event) => exit.add(event),
    );
    // Only respond to some mouse events.
    final MouseTrackerAnnotation partialAnnotation = MouseTrackerAnnotation(
      onEnter: (PointerEnterEvent event) => enter.add(event),
      onHover: (PointerHoverEvent event) => move.add(event),
    );
    bool isInHitRegionOne;
    bool isInHitRegionTwo;
  
    void clear() {
      enter.clear();
      exit.clear();
      move.clear();
    }
  
    setUp(() {
  
negative.code: 
      ui.window.onPointerDataPacket(packet1);
  
      expect(events, _equalToEventsOnCriticalFields(<PointerEvent>[
        const PointerEnterEvent(position: Offset(0.0, 0.0)),
        const PointerHoverEvent(position: Offset(0.0, 0.0)),
        const PointerHoverEvent(position: Offset(1.0, 101.0)),
      ]));
      // Simulate layer going away by detaching it.
      clear();
      isInHitRegionOne = false;
  
      ui.window.onPointerDataPacket(packet2);
      expect(events, _equalToEventsOnCriticalFields(<PointerEvent>[
        const PointerExitEvent(position: Offset(1.0, 201.0)),
      ]));
  
      // Actually detach annotation. Shouldn't receive hit.
      RendererBinding.instance.mouseTracker.detachAnnotation(annotation);
  