Missing scrolling inertia on iPadOS when using trackpad

Steps to Reproduce

Execute flutter run on the code sample
Connect an external trackpad to iPad (in this case, I am using the Magic Keyboard)
Use the two-finger scroll gesture

Expected results:
Scrolling animation should not stop when I lift my fingers from the trackpad. It should have inertia, just like when using touch input or when scrolling on computers.

Actual results:
Scrolling animation stops abruptly when I lift my fingers from the trackpad.

Code sample

import 'package:flutter/material.dart';

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

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

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({Key? key, required this.title}) : super(key: key);

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    var text = "Example Text ";
    for (var i in Iterable.generate(100)) {
      text = text + i.toString() + '\n';
    }
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: SingleChildScrollView(
        child: Text(
          text,
        ),
      ),
    );
  }
}

Logs

No log at all! even with --verbose (except at build time) 
I guess scroll event simply isn't logged.

Analyzing flutter_application_1...                                      
No issues found! (ran in 3.0s)

[✓] Flutter (Channel stable, 2.8.1, on macOS 12.1 21C52 darwin-x64, locale en-US)
    • Flutter version 2.8.1 at /Users/user/Projects/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 77d935af4d (5 weeks ago), 2021-12-16 08:37:33 -0800
    • Engine revision 890a5fca2e
    • Dart version 2.15.1

[✗] Android toolchain - develop for Android devices
    ✗ Unable to locate Android SDK.
      Install Android Studio from: https://developer.android.com/studio/index.html
      On first launch it will assist you in installing the Android SDK components.
      (or visit https://flutter.dev/docs/get-started/install/macos#android-setup for detailed instructions).
      If the Android SDK has been installed to a custom location, please use
      `flutter config --android-sdk` to update to that location.


[✓] Xcode - develop for iOS and macOS (Xcode 13.2.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • CocoaPods version 1.11.2

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[!] 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/macos#android-setup for detailed instructions).

[✓] VS Code (version 1.63.2)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.32.0

[✓] Connected device (3 available)
(devices omitted)

Video:

RPReplay_Final1642906616.MP4

Comparing trackpad scroll vs finger scroll (the transparent dot indicates trackpad is being used)

@singularity-s0

@singularity-s0
By missing scrolling inertia, do you mean when we try to flung scrollbar, it doesn't scroll correct ?
If so, can you check if this issue is similar to your case ?

@singularity-s0

@singularity-s0

By missing scrolling inertia, do you mean when we try to flung scrollbar, it doesn't scroll correct ?

If so, can you check if this issue is similar to your case ?

Hi, thanks for the reply.

No, this issue has nothing to do with scrollbar. As you can see in the video no scrollbar activity is involved.

This issue occurs when one uses the two-finger scroll gesture on external trackpads connected to an iPad. It is quite obvious.

Scrolling with other input is not affected.

@singularity-s0

@singularity-s0
Can you try to see what does ScrollPosition.isScrollingNotifier returns if you use two-finger gesture to scroll using trackpad ? Does it return false or true using something like:

final ScrollController controller = ScrollController();

  @override
  void initState() {
    controller.addListener(() {
      // always prints "scrolling = true"
      print('scrolling = ${controller.position.isScrollingNotifier.value}');
    });
    super.initState();
  }

  @override
  void dispose() {
    controller.dispose();
    super.dispose();
  }

It prints false when scrolling with trackpad and true when scrolling with finger.

@singularity-s0

@singularity-s0
Thanks for verifying. Based on your finding, I believe you are hitting #75591, so I suggest you to follow-up in it for further updates.
Closing this as a duplicate. If you disagree, write in comments and I'll reopen it.

This thread has been automatically locked since there has not been any recent activity after it was closed. If you are still experiencing a similar issue, please open a new bug, including the output of flutter doctor -v and a minimal reproduction of the issue.

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Missing scrolling inertia on iPadOS when using trackpad #97084

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Missing scrolling inertia on iPadOS when using trackpad #97084

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darshankawar commented on Jan 24, 2022

singularity-s0 commented on Jan 24, 2022

darshankawar commented on Jan 25, 2022

singularity-s0 commented on Jan 25, 2022

darshankawar commented on Jan 26, 2022

github-actions commented on Feb 9, 2022

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