Scroll performance significantly degraded on iPhone X, Xs devices due to irregular input events delivery. #31086
Description
Myself and some others discussing in #22314 have noticed significant scroll performance issues on iPhone X,Xs devices with scrolling views.
Anecdotally it seems drag gestures are the main issue, while flings seem slightly better.
@coreysprague suggested it may be because these devices have a 120hz gesture sample rate (https://www.macworld.com/article/3235709/iphone-x-samples-touch-input-at-120hz-for-faster-smoother-response.html).
Just want to clarify that this does happen even when running in release mode.
Steps to Reproduce
Here's a tiny sample app where you can reproduce the scroll jitters and frame skips, just grab an iPhone X,Xs and run in release mode.
import 'package:flutter/material.dart';
void main() => runApp(MyApp());
class MyApp extends StatelessWidget {
@override
Widget build(BuildContext context) {
const padding = EdgeInsets.symmetric(vertical: 10, horizontal: 10);
return MaterialApp(
home: Scaffold(
body: ListView(
children: <Widget>[
Container(
margin: padding,
height: 200,
color: Colors.grey,
),
Container(
margin: padding,
height: 200,
color: Colors.orange,
),
Container(
margin: padding,
height: 200,
color: Colors.grey,
),
Container(
margin: padding,
height: 200,
color: Colors.orange,
),
Container(
margin: padding,
height: 200,
color: Colors.grey,
),
Container(
margin: padding,
height: 200,
color: Colors.orange,
),
Container(
margin: padding,
height: 200,
color: Colors.grey,
),
Container(
margin: padding,
height: 200,
color: Colors.orange,
),
],
),
),
);
}
}Logs
No errors in logs w/ flutter run --verbose
No issued found w/ flutter analyze
[✓] Flutter (Channel stable, v1.2.1, on Mac OS X 10.14.4 18E226, locale en-US)
• Flutter version 1.2.1 at /Users/dwempe/flutter
• Framework revision 8661d8a (8 weeks ago), 2019-02-14 19:19:53 -0800
• Engine revision 3757390
• Dart version 2.1.2 (build 2.1.2-dev.0.0 0a7dcf17eb)
[✓] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
• Android SDK at /Users/dwempe/Library/Android/sdk
• Android NDK location not configured (optional; useful for native profiling support)
• Platform android-28, build-tools 28.0.3
• Java binary at: /Applications/Android Studio 2.app/Contents/jre/jdk/Contents/Home/bin/java
• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1248-b01)
• All Android licenses accepted.
[✓] iOS toolchain - develop for iOS devices (Xcode 10.2)
• Xcode at /Applications/Xcode.app/Contents/Developer
• Xcode 10.2, Build version 10E125
• ios-deploy 1.9.4
• CocoaPods version 1.5.3
[✓] Android Studio (version 3.3)
• Android Studio at /Applications/Android Studio 2.app/Contents
• Flutter plugin version 34.0.1
• Dart plugin version 182.5215
• Java version OpenJDK Runtime Environment (build 1.8.0_152-release-1248-b01)
[✓] VS Code (version 1.33.0)
• VS Code at /Applications/Visual Studio Code.app/Contents
• Flutter extension version 2.24.0
[✓] Connected device (2 available)
• Android SDK built for x86 • emulator-5554 • android-x86 • Android 8.0.0 (API 26)
(emulator)
• _________ iPhone • 00008020-000B25CE0298002E • ios • iOS 12.2
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Repeatedly frustrating issues with non-experimental functionalityRelates to speed or footprint issues (see "perf:" labels)Affects or could affect many people, though not necessarily a specific customer.Only manifests on certain devicesflutter/engine related. See also e: labels.Viewports, list views, slivers, etc.iOS applications specifically