Demo Flutter app to show how one can blow up memory by having many picture raster caches.

main.dart

import 'package:flutter/material.dart';

void main() {
  runApp(CacheMemTestApp());
}

class CacheMemTestApp extends StatefulWidget {
  @override
  State<StatefulWidget> createState() {
    return CacheMemTestAppState();
  }
}

class CacheMemTestAppState extends State<CacheMemTestApp> {
  static const int kMaxCount = 20;

  int count = 1;

  @override
  Widget build(BuildContext context) {
    final List<Color> colors = [Colors.red, Colors.green, Colors.blue];
    final List<CacheBlock> blocks = [];
    for (int i = 0; i < count; i += 1) {
      blocks.add(CacheBlock(
        colors[i % colors.length],
        Offset(i * 10.0, i * 10.0),
      ));
    }

    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: Scaffold(
        body: Center(
          child: ListView(
            children: [
              Stack(
                children: blocks,
              )
            ],
          ),
        ),
        floatingActionButton: FloatingActionButton(
          onPressed: () {
            setState(() {
              count += 1;
              count -= count > kMaxCount ? kMaxCount : 0;
            });
          },
          child: Text('+'),
        ),
      ),
    );
  }
}

class CacheBlock extends StatelessWidget {
  CacheBlock(this.color, this.offset);

  final Color color;
  final Offset offset;

  @override
  Widget build(BuildContext context) {
    return Transform.translate(
      offset: offset,
      child: RepaintBoundary(
        child: CustomPaint(
          painter: CacheBlockPainter(color),
          isComplex: true,
          willChange: false,
          child: Container(
            width: 2000,
            height: 2000,
          ),
        ),
      ),
    );
  }
}

class CacheBlockPainter extends CustomPainter {
  CacheBlockPainter(this.color);

  final Color color;

  @override
  void paint(Canvas canvas, Size size) {
    canvas.drawRect(Offset.zero & size, Paint()..color = color.withOpacity(0.5));
  }

  @override
  bool shouldRepaint(covariant CustomPainter oldDelegate) => true;
}