[Linux] Not clearing backbuffer before drawing.

[gspencergoog]

On the main branch, I created this very simple Flutter app:

import 'package:flutter/material.dart';

/// Flutter code sample for [MenuAnchor].

void main() {
  debugFocusChanges = false;
  runApp(const MenuApp());
}

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

  @override
  Widget build(BuildContext context) {
    final ThemeData theme = ThemeData.from(colorScheme: const ColorScheme.light());

    return MaterialApp(
        theme: theme,
        home: Center(
          child: Column(
            children: <Widget>[
              FilledButton.tonal(
                onPressed: () { },
                child: const Text('Tonal'),
              ),
              FilledButton.tonalIcon(
                onPressed: () { },
                icon: const Icon(Icons.add),
                label: const Text('TonalIcon'),
              ),
            ],
          ),
        ),
      );
  }
}

And ran it on my Linux machine, I got a window that didn't clear the backbuffer when switching buffers, leaving an interesting artifact filled image.

output.mp4

flutter doctor -v

[✓] Flutter (Channel main, 3.20.0-7.0.pre.31, on Debian GNU/Linux rodete 6.5.13-1rodete2-amd64, locale en_US.UTF-8)
    • Flutter version 3.20.0-7.0.pre.31 on channel main at /usr/local/google/home/gspencer/code/flutter
    • Upstream repository git@github.com:flutter/flutter.git
    • Framework revision 5025681129 (57 minutes ago), 2024-02-13 21:48:41 +0000
    • Engine revision 0091a4914d
    • Dart version 3.4.0 (build 3.4.0-138.0.dev)
    • DevTools version 2.33.0-dev.6

[✓] Android toolchain - develop for Android devices (Android SDK version 32.1.0-rc1)
    • Android SDK at /usr/local/google/home/gspencer/Android/Sdk
    • Platform android-33, build-tools 32.1.0-rc1
    • ANDROID_HOME = /usr/local/google/home/gspencer/Android/Sdk
    • Java binary at: /usr/bin/java
    • Java version OpenJDK Runtime Environment (build 17.0.10+7-Debian-1)
    • All Android licenses accepted.

[✓] Chrome - develop for the web
    • Chrome at google-chrome

[✓] Linux toolchain - develop for Linux desktop
    • Debian clang version 16.0.6 (16)
    • cmake version 3.27.7
    • ninja version 1.11.1
    • pkg-config version 1.8.1

[!] Android Studio (not installed)
    • Android Studio not found; download from https://developer.android.com/studio/index.html
      (or visit https://flutter.dev/docs/get-started/install/linux#android-setup for detailed instructions).

[✓] Connected device (2 available)
    • Linux (desktop) • linux  • linux-x64      • Debian GNU/Linux rodete 6.5.13-1rodete2-amd64
    • Chrome (web)    • chrome • web-javascript • Google Chrome 121.0.6167.160

[✓] Network resources
    • All expected network resources are available.

! Doctor found issues in 1 category.

[danagbemava-nc]

I could not reproduce this on my system using the example provided above.

Labeling based on the report shared above.

Screencast.from.14-02-24.08.52.02.webm

flutter doctor -v

[!] Flutter (Channel master, 3.20.0-7.0.pre.43, on Ubuntu 22.04.3 LTS 6.5.0-17-generic, locale en_US.UTF-8)
    • Flutter version 3.20.0-7.0.pre.43 on channel master at /home/daniel/fvm/versions/master
    ! Warning: `flutter` on your path resolves to /home/daniel/fvm/versions/stable/bin/flutter, which is not inside your current Flutter SDK checkout at /home/daniel/fvm/versions/master. Consider adding /home/daniel/fvm/versions/master/bin to the front of your path.
    ! Warning: `dart` on your path resolves to /home/linuxbrew/.linuxbrew/Cellar/dart/3.2.2/libexec/bin/dart, which is not inside your current Flutter SDK checkout at /home/daniel/fvm/versions/master. Consider adding /home/daniel/fvm/versions/master/bin to the front of your path.
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 295eeaf100 (5 hours ago), 2024-02-13 19:58:58 -0800
    • Engine revision 3af336bfb2
    • Dart version 3.4.0 (build 3.4.0-140.0.dev)
    • DevTools version 2.33.0-dev.6
    • If those were intentional, you can disregard the above warnings; however it is recommended to use "git" directly to perform update checks and upgrades.

[✓] Android toolchain - develop for Android devices (Android SDK version 34.0.0)
    • Android SDK at /home/daniel/Android/Sdk
    • Platform android-34, build-tools 34.0.0
    • Java binary at: /home/daniel/.local/share/JetBrains/Toolbox/apps/android-studio/jbr/bin/java
    • Java version OpenJDK Runtime Environment (build 17.0.7+0-17.0.7b1000.6-10550314)
    • All Android licenses accepted.

[✓] Chrome - develop for the web
    • Chrome at google-chrome

[✓] Linux toolchain - develop for Linux desktop
    • Ubuntu clang version 14.0.0-1ubuntu1.1
    • cmake version 3.22.1
    • ninja version 1.10.1
    • pkg-config version 0.29.2

[✓] Android Studio (version 2023.1)
    • Android Studio at /home/daniel/.local/share/JetBrains/Toolbox/apps/android-studio
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build 17.0.7+0-17.0.7b1000.6-10550314)

[✓] VS Code (version 1.85.1)
    • VS Code at /usr/share/code
    • Flutter extension version 3.82.0

[✓] Connected device (2 available)
    • Linux (desktop) • linux  • linux-x64      • Ubuntu 22.04.3 LTS 6.5.0-17-generic
    • Chrome (web)    • chrome • web-javascript • Google Chrome 120.0.6099.129

[✓] Network resources
    • All expected network resources are available.

! Doctor found issues in 1 category.

[cbracken]

I'm able to replicate this on Ubuntu 22.04 running with XDG_SESSION_TYPE=x11. I tried to bisect this to figure out when it was introduced, but I'm able to replicate this issue all the way back to 2022-01-01, so I'm wondering if a newer version of underlying libraries has revealed an issue in the existing implementation.

This did not repro on another machine runnign Ubuntu 22.04 using wayland, and this definitely worked on older versions under X11.

@gspencergoog can you confirm whether you're using X11 or Wayland?
@danagbemava-nc are you using X11 or Wayland?

[cbracken]

/cc @robert-ancell

[robert-ancell]

Does it occur with the rendering changes in flutter/engine#50754?