[web]: When scrolling anywhere on the page, console keeps reporting "Uncaught Error: Assertion failed: is not true"

[sgon00]

Flutter version

[✓] Flutter (Channel dev, v1.5.8, on Mac OS X 10.13.6 17G4015, locale en-CN)

Workflow, use stagehand:

$ mkdir foo && cd foo
$ stagehand flutter-web-preview
$ flutter packages pub global activate webdev
$ flutter packages pub upgrade
$ flutter packages pub global run webdev serve

And then open chrome debug console and trying to scroll anywhere on the page (I am on MacBook, so basically using two fingers on the touchpad and then move Up and Down)

The error:

dart_sdk.js:5844 Uncaught Error: Assertion failed: is not true
    at Object.dart.throw (dart_sdk.js:4556)
    at Object.dart.assertFailed (dart_sdk.js:4495)
    at SyncIterable.new.expand (converter.dart:432)
    at expand.next (<anonymous>)
    at ListQueue.new.addAll (dart_sdk.js:31511)
    at src__widgets__binding.WidgetsFlutterBinding.new.[_handlePointerDataPacket] (binding.dart:85)
    at src__engine.PointerBinding.new.[_onPointerData] (pointer_binding.dart:80)
    at pointer_binding.dart:205
    at HTMLElement.<anonymous> (pointer_binding.dart:449)

Gif Video:

[yjbanov]

This might have been fixed by https://github.com/flutter/flutter_web/commit/c4cfaecebc5ef97500db2be0bd99e52d1e5e16c2. Please reopen if you see this again.

[jegathispandian]

Still i am facing this issue

[yjbanov]

I think I saw this too recently. Reopening.

/cc @ferhatb

[kechankrisna]

I just got the same issue now,
![](https://raw.githubusercontent.com/kechankrisna/kechankrisna.github.io/master/errors/err1.png)

[Shafran123]

I am also facing this issue!

[kynrai]

same, happy to help how I can to resolve this

[miketheman]

Seen on recent beta channel, and current error message:

doctor:

[✓] Flutter (Channel beta, v1.12.13+hotfix.6, on Mac OS X 10.14.6 18G2022, locale en-US)

devices:

Chrome     • chrome     • web-javascript • Google Chrome 79.0.3945.88
Web Server • web-server • web-javascript • Flutter Tools

errors.dart:147 Uncaught Error: Assertion failed: org-dartlang-sdk:///flutter_web_sdk/lib/_engine/engine/pointer_converter.dart:271:18
!state.down
is not true
    at Object.throw_ [as throw] (errors.dart:196)
    at Object.assertFailed (errors.dart:26)
    at _engine.PointerDataConverter.new.convert (pointer_converter.dart:271)
    at _engine.PointerAdapter.new.[_convertEventToPointerData] (pointer_binding.dart:366)
    at pointer_binding.dart:317
    at HTMLElement.<anonymous> (pointer_binding.dart:183)

Possibly the same as #46852 ?

[dkwingsmt]

#47492 might be a fix if your problem is an assertion error when scrolling (especially considering the change that this PR tries to fix was merged in May).

[ferhatb]

/cc @mdebbar , we can close this now since fixed in master?

[mdebbar]

There are multiple errors reported in this issue.

• The original error reported in this issue was fixed by https://github.com/flutter/flutter_web/commit/c4cfaecebc5ef97500db2be0bd99e52d1e5e16c2, add pointer data santizing in flutter web engine engine#14082 and [Web] Fix pointer binding  engine#14378.
• Scrolling errors were fixed by Registering multiple transformed events should work #48149 and Add test of scrolling competition #47492.
• Right-click and state.down errors were fixed by [web] Fix right click issues engine#15103.

If you are still seeing similar errors, please file an issue for the specific error so we can investigate.