onKeyEvent doesn't work if you press two buttons.

[bernaferrari]

How to reproduce:

• Press "arrow right".
• Press "arrow up".
• Take the finger out from "arrow up".
• onKeyEvent will stop triggering.

Screen.Recording.2022-12-30.at.19.04.01.mov

Really simple code:

  @override
  KeyEventResult onKeyEvent(
      RawKeyEvent event, Set<LogicalKeyboardKey> keysPressed) {
  print('keysPressed: ${keysPressed.map((e) => e.keyLabel)}');
   return super.onKeyEvent(event, keysPressed);
}

Using Flame 1.5.0 and Flutter (Channel main, 3.7.0-13.0.pre.127, on macOS 13.1 22C65 darwin-x64,
locale en-BR)

[spydon]

Have you tried on the stable channel of Flutter?

[bernaferrari]

Yes, same issue.

[spydon]

Very strange, this definitely used to work! It seems to not happen all the time either.
I would guess that this is a Flutter bug, so it would be good to try this in a pure Flutter app.

Here is a full repro if anyone wants to try:
https://dartpad.dev/?id=96f38607b6d255a7c9b7b19954ec19a6

[bernaferrari]

For me, Flutter-only seems to be working fine.

This is an old sample, it is working:

import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(),
      home: const HomePage(),
    );
  }
}

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

  @override
  State<HomePage> createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Focus(
        autofocus: true,
        onKey: (FocusNode node, RawKeyEvent event) {
          KeyEventResult result = KeyEventResult.ignored;
          if (event is RawKeyDownEvent) {
            if (event.logicalKey == LogicalKeyboardKey.keyZ ||
                event.logicalKey == const LogicalKeyboardKey(0x0000005a)) {
              // When press Z, ctrl+Z, meta+Z, shift+Z:
              print('Z pressed');
              result = KeyEventResult.handled;
            } else {
              // When press meta+shift+Z.
              print('something pressed (???)');
            }
          }
          setState(() {});
          return result;
        },
        child: Text('key is: ${RawKeyboard.instance.keysPressed}'),
      ),
    );
  }
}

[bernaferrari]

Hold on. Still debugging.

[bernaferrari]

This is not a Flutter issue, this is how the OS works. These are the possible workarounds:

Also this:
flutter/flutter#117841 (comment)

[spydon]

This is not a Flutter issue, this is how the OS works. These are the possible workarounds:

Also this:
flutter/flutter#117841 (comment)

Thanks for investigating it! I guess we should close this then.

[bernaferrari]

Yes and no, ideally you could refactor onKeyEvent or add the proposed method into the framework, so would help more people, as the behavior will probably be unclear for many (like Bonfire, etc), and this affects 90% of games.

[bernaferrari]

I made a sketch for a mixin that could somewhat be integrated into Flame, since it guarantees the button works. Just giving the idea. But ideally you could override onKeyEvent with the new system, so existing apps keep working and the bug is gone. currentKeysPressed should become keysPressed:

mixin WithCorrectTimer on Component, HasKeyboardHandlerComponents {
  Timer? _timer;
  final Set<String?> currentKeysPressed = {};
  final int interval = 16;

  @override
  Future<void>? onLoad() {
    _timer?.cancel();
    _timer = Timer.periodic(
        Duration(milliseconds: interval), (Timer t) => updateMovement());
    return super.onLoad();
  }

  void updateMovement();

  @override
  void onRemove() {
    _timer?.cancel();
    super.onRemove();
  }

  @override
  KeyEventResult onKeyEvent(
      RawKeyEvent event, Set<LogicalKeyboardKey> keysPressed) {
    currentKeysPressed
      ..clear()
      ..addAll(RawKeyboard.instance.keysPressed.map((e) => e.debugName));
    return super.onKeyEvent(event, keysPressed);
  }
}

[spydon]

You shouldn't need the timer if you use on Component in the mixin, then you can hook in and use update instead.

[st-pasha]

My worry here is that there could be a situation where a key gets released without the corresponding "KeyUp" event -- say it gets released when the game widget has no focus. In that case we would keep thinking that the key is pressed, and it will effectively become "stuck".

[st-pasha]

But perhaps we could create a new version of the KeyboardEvents mixin, allowing the people to gradually transition, with the possibility of falling back to the old mixin if something is not working. Similar to how we introduced new draggables and tappables mixins.

[bernaferrari]

My worry here is that there could be a situation where a key gets released without the corresponding "KeyUp" event

There is a Flutter "bug" that already happens when you switch window. It will be fixed in the coming months when the key behavior is synced across window.

Right NOW, the only way to not trigger the bug behavior is using ShortcutActivator or SingleActivator, which you aren't using on keyboard event. So there wouldn't be any change.

[bernaferrari]

I can't believe you worked so hard on it. I thought I was happy with my placeholder (which came from you, lol). And you ended up doing something even better. Thanks!!