constantly repainting RO

main.dart

import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';
import 'package:flutter/scheduler.dart';
import 'package:flutter_svg/svg.dart';

void main() {
  runApp(const MaterialApp(home: Scaffold(body: Example())));
}

class Example extends StatefulWidget {
  const Example({ Key? key }) : super(key: key);

  @override
  _ExampleState createState() => _ExampleState();
}

class _ExampleState extends State<Example> {
  @override
  void initState() {
    super.initState();
    SchedulerBinding.instance!.addPostFrameCallback(_extraPaint);
  }

  void _extraPaint(Duration _) {
    setState(() {});
    SchedulerBinding.instance!.addPostFrameCallback(_extraPaint);
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      child: ExtraPaintWidget(child: SvgPicture.asset('assets/wikimedia/Ghostscript_Tiger.svg')),
    );
  }
}

class ExtraPaintWidget extends SingleChildRenderObjectWidget {
  ExtraPaintWidget({required Widget child}) : super(child: child);

  @override
  RenderObject createRenderObject(BuildContext context) {
    return ExtraPaintRO();
  }

  @override
  void updateRenderObject(BuildContext context, covariant ExtraPaintRO renderObject) {
    renderObject.dirty = 2;
  }
}

class ExtraPaintRO extends RenderProxyBox {
  set dirty(int value) {
    markNeedsPaint();
  }
}