TextField onChange method inconsistent when characters are spammed

[ChunKaiC]

What the code sample does

I am trying to build a text editor on top of the TextField. The code sample format's the text within a text field, adding a line break at every 10th character.

Steps to Reproduce

1. Execute flutter run on the code sample
2. Simultaneously press multiple keys on the keyboard just before a line break occurs

Expected results: Text formatted correctly with a line break at every 10th character.

Actual results: Sometimes the formatting method within onChange does not apply correctly, meaning a line can exceed 10 characters before a line break. Occasionally some characters typed are deleted.

Code sample

```import 'package:flutter/material.dart'; import 'package:google_fonts/google_fonts.dart'; void main() { runApp(const MyApp()); } class MyApp extends StatelessWidget { const MyApp({super.key}); // This widget is the root of your application. @override Widget build(BuildContext context) { return MaterialApp( title: 'Flutter Demo', theme: ThemeData(primarySwatch: Colors.blue), home: const TestEditor(), ); } } class TestEditor extends StatefulWidget { const TestEditor({super.key}); @override State createState() => _TestEditorState(); } class _TestEditorState extends State { final contoller = TextEditingController(); void onChange(String text) { // Method 1 if (text.length % 10 == 0 && text.isNotEmpty) { final selection = contoller.selection.copyWith(); contoller.text += '\n'; contoller.selection = selection.copyWith( baseOffset: selection.baseOffset + 1, extentOffset: selection.extentOffset + 1, ); } } @override Widget build(BuildContext context) { return Scaffold( body: SafeArea( child: SizedBox( width: MediaQuery.of(context).size.width, height: MediaQuery.of(context).size.height, child: TextField( style: GoogleFonts.robotoMono(), cursorWidth: 2, controller: contoller, onChanged: onChange, showCursor: true, smartQuotesType: SmartQuotesType.disabled, smartDashesType: SmartDashesType.disabled, enableSuggestions: false, autocorrect: false, maxLines: 500, ), ), ), ); } } ```

Logs

``` N/A ``` ``` Analyzing bug_example... No issues found! (ran in 1.1s) ``` ``` [✓] Flutter (Channel stable, 3.3.6, on macOS 13.0 22A380 darwin-arm, locale en-CA) • Flutter version 3.3.6 on channel stable at /Users/chunkaic/Developement/flutter • Upstream repository https://github.com/flutter/flutter.git • Framework revision 6928314d50 (6 weeks ago), 2022-10-25 16:34:41 -0400 • Engine revision 3ad69d7be3 • Dart version 2.18.2 • DevTools version 2.15.0 [✓] Android toolchain - develop for Android devices (Android SDK version 32.1.0-rc1) • Android SDK at /Users/chunkaic/Library/Android/sdk • Platform android-32, build-tools 32.1.0-rc1 • Java binary at: /Applications/Android Studio.app/Contents/jre/Contents/Home/bin/java • Java version OpenJDK Runtime Environment (build 11.0.12+0-b1504.28-7817840) • All Android licenses accepted. [✓] Xcode - develop for iOS and macOS (Xcode 14.0.1) • Xcode at /Applications/Xcode.app/Contents/Developer • Build 14A400 • CocoaPods version 1.11.3 [✓] Chrome - develop for the web • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome [✓] Android Studio (version 2021.2) • Android Studio at /Applications/Android Studio.app/Contents • 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 11.0.12+0-b1504.28-7817840) [✓] VS Code (version 1.72.2) • VS Code at /Applications/Visual Studio Code.app/Contents • Flutter extension version 3.52.0 [✓] Connected device (3 available) • iPhone 14 Pro (mobile) • A0687B48-A2A3-4A34-991D-A88F4F0ABF47 • ios • com.apple.CoreSimulator.SimRuntime.iOS-16-0 (simulator) • macOS (desktop) • macos • darwin-arm64 • macOS 13.0 22A380 darwin-arm • Chrome (web) • chrome • web-javascript • Google Chrome 108.0.5359.94 [✓] HTTP Host Availability • All required HTTP hosts are available • No issues found! ```

[darshankawar]

Thanks for the report @ChunKaiC After running your code and inputing random text in the textfield, I see that first line gets 10 chars but other lines shows 9 chars as below:

Is that the behavior you are seeing and reporting ? Or you see another different result ?

[ChunKaiC]

Yes, my mistake, the screen shot you sent is the correct behaviour. The problem I'm currently experiencing is that sometimes when you spam right before a line break is about to be inserted this happens:

(This was done by pressing 'adsjkl' on the keyboard simultaneously)

No line break was inserted. Typing another character causes some characters to be deleted before being formatted:

(This was done by pressing 'd' after the previous screen shot)

This was found on the iOS simulator, however the problem seems to occur on iOS release mode as well.

[darshankawar]

Thanks for the update. Based on my findings earlier and above report, keeping this issue open for team's attention.

stable, master flutter doctor -v

``` [✓] Flutter (Channel stable, 3.3.9, on macOS 12.2.1 21D62 darwin-x64, locale en-GB) • Flutter version 3.3.9 on channel stable at /Users/dhs/documents/fluttersdk/flutter • Upstream repository https://github.com/flutter/flutter.git • Framework revision b8f7f1f986 (12 days ago), 2022-11-23 06:43:51 +0900 • Engine revision 8f2221fbef • Dart version 2.18.5 • DevTools version 2.15.0 [!] Xcode - develop for iOS and macOS (Xcode 12.3) • Xcode at /Applications/Xcode.app/Contents/Developer ! Flutter recommends a minimum Xcode version of 13. Download the latest version or update via the Mac App Store. • CocoaPods version 1.11.2 [✓] Chrome - develop for the web • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome [✓] VS Code (version 1.62.0) • VS Code at /Applications/Visual Studio Code.app/Contents • Flutter extension version 3.21.0 [✓] Connected device (5 available) • SM G975F (mobile) • RZ8M802WY0X • android-arm64 • Android 11 (API 30) • Darshan's iphone (mobile) • 21150b119064aecc249dfcfe05e259197461ce23 • ios • iOS 14.4.1 18D61 • iPhone 12 Pro Max (mobile) • A5473606-0213-4FD8-BA16-553433949729 • ios • com.apple.CoreSimulator.SimRuntime.iOS-14-3 (simulator) • macOS (desktop) • macos • darwin-x64 • Mac OS X 10.15.4 19E2269 darwin-x64 • Chrome (web) • chrome • web-javascript • Google Chrome 98.0.4758.80 [✓] HTTP Host Availability • All required HTTP hosts are available ! Doctor found issues in 1 category. [!] Flutter (Channel master, 3.7.0-4.0.pre.48, on macOS 12.2.1 21D62 darwin-x64, locale en-GB) • Flutter version 3.7.0-4.0.pre.48 on channel master at /Users/dhs/documents/fluttersdk/flutter ! Warning: `flutter` on your path resolves to /Users/dhs/Documents/Fluttersdk/flutter/bin/flutter, which is not inside your current Flutter SDK checkout at /Users/dhs/documents/fluttersdk/flutter. Consider adding /Users/dhs/documents/fluttersdk/flutter/bin to the front of your path. ! Warning: `dart` on your path resolves to /Users/dhs/Documents/Fluttersdk/flutter/bin/dart, which is not inside your current Flutter SDK checkout at /Users/dhs/documents/fluttersdk/flutter. Consider adding /Users/dhs/documents/fluttersdk/flutter/bin to the front of your path. • Upstream repository https://github.com/flutter/flutter.git • Framework revision eefbe85c8b (19 minutes ago), 2022-12-08 22:32:07 -0600 • Engine revision 8d83b98c55 • Dart version 3.0.0 (build 3.0.0-0.0.dev) • DevTools version 2.20.0 • If those were intentional, you can disregard the above warnings; however it is recommended to use "git" directly to perform update checks and upgrades. [!] Xcode - develop for iOS and macOS (Xcode 12.3) • Xcode at /Applications/Xcode.app/Contents/Developer ! Flutter recommends a minimum Xcode version of 13. Download the latest version or update via the Mac App Store. • CocoaPods version 1.11.2 [✓] Chrome - develop for the web • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome [✓] VS Code (version 1.62.0) • VS Code at /Applications/Visual Studio Code.app/Contents • Flutter extension version 3.21.0 [✓] Connected device (5 available) • SM G975F (mobile) • RZ8M802WY0X • android-arm64 • Android 11 (API 30) • Darshan's iphone (mobile) • 21150b119064aecc249dfcfe05e259197461ce23 • ios • iOS 14.4.1 18D61 • iPhone 12 Pro Max (mobile) • A5473606-0213-4FD8-BA16-553433949729 • ios • com.apple.CoreSimulator.SimRuntime.iOS-14-3 (simulator) • macOS (desktop) • macos • darwin-x64 • Mac OS X 10.15.4 19E2269 darwin-x64 • Chrome (web) • chrome • web-javascript • Google Chrome 98.0.4758.80 [✓] HTTP Host Availability • All required HTTP hosts are available ! Doctor found issues in 1 category. ```

[justinmc]

CC @LongCatIsLooong