Flutter Web - Как сохранить изображение, созданное с помощью виджета CustomPaint, на Flutter Web

Question

Я портирую мобильное приложение на Интернет, это приложение использует виджет CustomPaint для рисования на основе пользовательских данных. С RepaintBoundary я делаю снимок экрана с краской и сохраняю его на устройстве, используя пакет save_in_gallery.dart.

В веб-приложении чертежная часть работает нормально, но я не могу получить часть снимка экрана или часть сохранения изображения на работу. Вот код, который я использую для сохранения

    RenderRepaintBoundary boundary =
        globalKey.currentContext.findRenderObject();
    ui.Image image = await boundary.toImage();
    ByteData byteData = await image.toByteData(format: ui.ImageByteFormat.png);
    Uint8List pngBytes = byteData.buffer.asUint8List();
    final res = await _imageSaver.saveImage(
      imageBytes: pngBytes,
      directoryName: "dir_name",
    );
    print(res);
    print(pngBytes);
  } 

Вот ошибка на консоли chrome, когда я нажимаю кнопку, которая активирует RepaintBoundary (снимок экрана), и функцию сохранения:

errors.dart:146 Uncaught (in promise) Error: Exception: Incorrect sequence of push/pop operations while building scene surfaces. After building the scene the persisted surface stack must contain a single element which corresponds to the scene itself (_PersistedScene). All other surfaces should have been popped off the stack. Found the following surfaces in the stack:
PersistedScene, PersistedTransform
    at Object.throw_ [as throw] (errors.dart:195)
    at scene_builder.dart:27
    at _engine.SurfaceSceneBuilder.new.get [_persistedScene] (scene_builder.dart:34)
    at _engine.SurfaceSceneBuilder.new.build (scene_builder.dart:544)
    at layer$.OffsetLayer.new.buildScene (layer.dart:808)
    at layer$.OffsetLayer.new.toImage (layer.dart:1241)
    at toImage.next (<anonymous>)
    at runBody (async_patch.dart:86)
    at Object._async [as async] (async_patch.dart:125)
    at layer$.OffsetLayer.new.toImage (layer.dart:1230)
    at proxy_box.RenderRepaintBoundary.new.toImage (proxy_box.dart:2963)
    at DrawCustomPainter._DrawCustomPainterState.new._capturePng (DrawCustomPainter.dart:37)
    at _capturePng.next (<anonymous>)
    at runBody (async_patch.dart:86)
    at Object._async [as async] (async_patch.dart:125)
    at DrawCustomPainter._DrawCustomPainterState.new.[_capturePng] (DrawCustomPainter.dart:34)
    at _InkResponseState.new.[_handleTap] (ink_well.dart:779)
    at ink_well.dart:862
    at tap.TapGestureRecognizer.new.invokeCallback (recognizer.dart:182)
    at tap.TapGestureRecognizer.new.handleTapUp (tap.dart:504)
    at tap.TapGestureRecognizer.new.[_checkUp] (tap.dart:282)
    at tap.TapGestureRecognizer.new.acceptGesture (tap.dart:254)
    at arena.GestureArenaManager.new.sweep (arena.dart:156)
    at binding$5.WidgetsFlutterBinding.new.handleEvent (binding.dart:222)
    at binding$5.WidgetsFlutterBinding.new.dispatchEvent (binding.dart:198)
    at binding$5.WidgetsFlutterBinding.new.[_handlePointerEvent] (binding.dart:156)
    at binding$5.WidgetsFlutterBinding.new.[_flushPointerEventQueue] (binding.dart:102)
    at binding$5.WidgetsFlutterBinding.new.[_handlePointerDataPacket] (binding.dart:86)
    at Object._invoke1 (window.dart:590)
    at _engine.EngineWindow.new.invokeOnPointerDataPacket (window.dart:238)
    at _engine.PointerBinding.__.[_onPointerData] (pointer_binding.dart:129)
    at pointer_binding.dart:457
    at pointer_binding.dart:418
    at HTMLElement.<anonymous> (pointer_binding.dart:195)