A simple flutter widget that can simulate/fake a different pixel ratio for all it's children. Can be the root widget, i.e. the widget given to runApp(). Useful for when your device/emulator doesn't properly calculate the devicePixelRatio.

fakedevicepixelratio.dart

import 'package:flutter/widgets.dart';

class FakeDevicePixelRatio extends StatelessWidget {
  final num fakeDevicePixelRatio;
  final Widget child;

  FakeDevicePixelRatio({this.fakeDevicePixelRatio, this.child}) : assert(fakeDevicePixelRatio != null);

  @override
  Widget build(BuildContext context) {
    final ratio = fakeDevicePixelRatio / WidgetsBinding.instance.window.devicePixelRatio;
    
    return FractionallySizedBox(
      widthFactor: 1/ratio,
      heightFactor: 1/ratio,
      child: Transform.scale(
        scale: ratio,
        child: child
      )
    );
  }
}

Thanks for sharing!

updated it to work with current version:

class _FakeDevicePixelRatio extends StatelessWidget {
  final num fakeDevicePixelRatio;
  final Widget child;

  const _FakeDevicePixelRatio({
    required this.fakeDevicePixelRatio,
    required this.child,
  });

  @override
  Widget build(BuildContext context) {
    final ratio = fakeDevicePixelRatio / MediaQuery.of(context).devicePixelRatio;

    return FractionallySizedBox(
      widthFactor: 1 / ratio,
      heightFactor: 1 / ratio,
      child: Transform.scale(
        scale: ratio,
        child: child,
      ),
    );
  }
}