InteractiveViewer's trackpadScrollCausesScale not reliable on web platform

[pathconnected]

Intro

This is related to the fact that currently there is no reliable way to distinguish mouse / trackpad scroll events on the web:

• Differentiate trackpad from mouse wheels on web #139990
• Web trackpad pan engine#36346
• Wheel event: determine difference between trackpad and mouse events w3c/pointerevents#596

Therefore on Firefox or on some OS trackpad events are registered as mouse events.

Steps to reproduce

1. Have an InteractiveViewer widget in a project with trackpadScrollCausesScale field set to false.
2. Open the project in Firefox, or on other browsers on windows / linux.
3. Scroll with a trackpad on top of it.

Expected results

The InteractiveViewer child is not scaled.

Actual results

The InteractiveViewer child is scaled.

Code sample

Code sample

import 'package:flutter/material.dart';

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

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

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

class MyHomePage extends StatelessWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        backgroundColor: Theme.of(context).colorScheme.inversePrimary,
        title: Text(title),
      ),
      body: Center(
        child: SizedBox.square(
          dimension: 300,
          child: InteractiveViewer(
            trackpadScrollCausesScale: false,
            child: Placeholder(),
          ),
        ),
      ),
    );
  }
}

Screenshots or Video

No response

Logs

Flutter Doctor output

Doctor output

[cloud@psi ~]$ flutter doctor
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 3.29.1, on Arch Linux 6.13.3-arch1-1, locale en_US.UTF-8)
[✓] Android toolchain - develop for Android devices (Android SDK version 35.0.0)
[✓] Chrome - develop for the web
[✓] Linux toolchain - develop for Linux desktop
[✓] Android Studio (version 2024.2)
[✓] IntelliJ IDEA Community Edition (version 2024.3)
[✓] Connected device (2 available)

[pathconnected]

I started to suspect that this widget was intended to be used in a "non-scrollable" context.

The reason why I find odd the reported behavior, and I also find odd the mouse-wheel behavior (not tested), is that I intended to use this widget inside a SingleChildScrollView or similar. In this situation on web platform & linux I get a scale + external scroll effect.

On mobile it works fine though. I do not really understand why there is a trackpadScrollCausesScale field.

[pathconnected]

Maybe I should just disable scale and handle scale differently. Sorry, I didn't think this issue through so I'm closing it.

[github-actions]

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.