anchor.diff:      _redraw.notify();
     }
   
  -  Artboard? instance() {
  +  @override
  +  Artboard instance() {
       var artboard = RuntimeArtboard();
  +    artboard.context = artboard;
       artboard.copy(this);
       artboard._objects.add(artboard);
       // First copy the objects ensuring onAddedDirty can later find them in the
       // _objects list.
       for (final object in _objects.skip(1)) {
         Core? clone = object?.clone();
  -      artboard._objects.add(clone);
  +      artboard.addObject(clone);
       }
   
       // Then run the onAddedDirty loop.
  
positive.code:   }
  
    @override
    Core<CoreContext>? makeCoreInstance(int typeKey) {
      return null;
    }
  
    @override
    void dirty(void Function() dirt) {
  
negative.code:       }
        object?.onAddedDirty();
      }
      animations.forEach(artboard.animations.add);
      for (final object in artboard.objects.toList(growable: false)) {
        if (object == null) {
          continue;
        }
        object.onAdded();
        InternalCoreHelper.markValid(object);
      }
      artboard.clean();
      return artboard;
    }
  }
  