anchor.diff:  // Use of this source code is governed by a BSD-style license that can be
   // found in the LICENSE file.
   
  -import 'dart:developer';
   import 'dart:ui' as ui show ImageFilter, Picture, SceneBuilder;
   import 'dart:ui' show Offset;
   
  
positive.code: 
    @override
    void addToScene(ui.SceneBuilder builder, Offset layerOffset) {
      Timeline.startSync('ChildSceneLayer::addToScene');
      builder.addChildScene(
        offset + layerOffset,
        devicePixelRatio,
  
negative.code:       physicalHeight,
        sceneToken.value
      );
    }
  
    @override
  