Matrix4.scale causes an error on macOS.

[shingo-nakanishi]

Reference: flame-engine/flame#3421

I encountered an error while trying to create a game using Flame. At first, I thought the issue was with Flame, but since I was able to reproduce it even without Flame, I'm posting about it.

code:

import 'package:flutter/material.dart';

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

class _MyApp extends StatelessWidget {
  const _MyApp({super.key});

  @override
  Widget build(BuildContext context) {
    final matrix = Matrix4.identity();
    matrix.scale(-1, 1);

    return const SizedBox();
  }
}

log:

══╡ EXCEPTION CAUGHT BY WIDGETS LIBRARY ╞═══════════════════════════════════════════════════════════
The following UnimplementedError was thrown building _MyApp(dirty):
UnimplementedError

The relevant error-causing widget was:
  _MyApp _MyApp:file:///project-folder/lib/main.dart:4:10

When the exception was thrown, this was the stack:
#0      Matrix4.scale (package:vector_math/src/vector_math_64/matrix4.dart:886:7)
#1      _MyApp.build (package:n_circle_page/main.dart:13:12)
#2      StatelessElement.build (package:flutter/src/widgets/framework.dart:5687:49)
#3      ComponentElement.performRebuild (package:flutter/src/widgets/framework.dart:5617:15)
#4      Element.rebuild (package:flutter/src/widgets/framework.dart:5333:7)
#5      ComponentElement._firstBuild (package:flutter/src/widgets/framework.dart:5599:5)
#6      ComponentElement.mount (package:flutter/src/widgets/framework.dart:5593:5)
...     Normal element mounting (63 frames)
#69     Element.inflateWidget (package:flutter/src/widgets/framework.dart:4468:16)
#70     Element.updateChild (package:flutter/src/widgets/framework.dart:3963:18)
#71     _RawViewElement._updateChild (package:flutter/src/widgets/view.dart:441:16)
#72     _RawViewElement.mount (package:flutter/src/widgets/view.dart:464:5)
...     Normal element mounting (15 frames)
#87     Element.inflateWidget (package:flutter/src/widgets/framework.dart:4468:16)
#88     Element.updateChild (package:flutter/src/widgets/framework.dart:3963:18)
#89     RootElement._rebuild (package:flutter/src/widgets/binding.dart:1605:16)
#90     RootElement.mount (package:flutter/src/widgets/binding.dart:1574:5)
#91     RootWidget.attach.<anonymous closure> (package:flutter/src/widgets/binding.dart:1527:18)
#92     BuildOwner.buildScope (package:flutter/src/widgets/framework.dart:3038:19)
#93     RootWidget.attach (package:flutter/src/widgets/binding.dart:1526:13)
#94     WidgetsBinding.attachToBuildOwner (package:flutter/src/widgets/binding.dart:1265:27)
#95     WidgetsBinding.attachRootWidget (package:flutter/src/widgets/binding.dart:1247:5)
#96     WidgetsBinding.scheduleAttachRootWidget.<anonymous closure> (package:flutter/src/widgets/binding.dart:1233:7)
#100    _RawReceivePort._handleMessage (dart:isolate-patch/isolate_patch.dart:184:12)
(elided 3 frames from class _Timer and dart:async-patch)

[spydon]

It's because you're using ints, try using doubles instead.

[spydon]

I guess we could just add a case for int here:
https://github.com/google/vector_math.dart/blob/master/lib%2Fsrc%2Fvector_math_64%2Fmatrix4.dart#L885

[shingo-nakanishi]

Ah, it's created with the dynamic type.

Still, it's strange that it's working in Chrome.
Could JavaScript's type be affecting Dart as well? (That can't be the case, right?)

[shingo-nakanishi]

For now, it worked on macOS with the following:
matrix.scale(-1.0, 1)

[spydon]

Could JavaScript's type be affecting Dart as well? (That can't be the case, right?)

Yes, it is since JS only have one type for both ints and doubles.