Repository: flutter
Issue: Text cursor flashes in magnifier
Labels: a: text input,framework,has reproducible steps,P2,found in release: 3.7,team-framework,triaged-framework

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## Steps to Reproduce

<!-- Please include full steps to reproduce so that we can reproduce the problem. -->

1. Use Flutter 3.7.0
1. Execute `flutter run` on the code sample <!-- (see "Code sample" section below) -->
1. Select textfield and input something
1. Move text selection handle

**Expected results:** <!-- what did you want to see? -->
not flashing

**Actual results:** <!-- what did you see? -->
the former handle is flashing.

https://user-images.githubusercontent.com/52235899/214505006-db283c40-3658-4b3f-afac-bbd63406dd31.mov





<details>
<summary>Code sample</summary>

<!--
      Please create a minimal reproducible sample that shows the problem
      and attach it below between the lines with the backticks.

      To create it you can use `flutter create bug` command and update the `main.dart` file.

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      which is capable of creating and running small Flutter apps.

      Without this we will unlikely be able to progress on the issue, and because of that
      we regretfully will have to close it.
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```dart
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',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: const MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  const MyHomePage({super.key, required this.title});

  final String title;

  @override
  State<MyHomePage> createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  @override
  Widget build(BuildContext context) {
    return Scaffold(
        // appBar: AppBar(title: Text(widget.title)), ////// Somehow, if you comment in this line, it looks working.
        body: const Center(
            child: TextField(
                maxLines: null,
                textInputAction: TextInputAction.newline,
                decoration: InputDecoration(isDense: true))));
  }
}

```

</details>

<details>
  <summary>Logs</summary>

<!--
      Run your application with `flutter run --verbose` and attach all the
      log output below between the lines with the backticks. If there is an
      exception, please see if the error message includes enough information
      to explain how to solve the issue. If there is a crash, please include
      the entirety of the crash log including the backtrace.
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```
```

<!--
     Run `flutter analyze` and attach any output of that command below.
     If there are any analysis errors, try resolving them before filing this issue.
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```
```

<!-- Finally, paste the output of running `flutter doctor -v` here. -->

```
[!] Flutter (Channel unknown, 3.7.0, on macOS 13.1 22C65 darwin-arm64, locale en-JP)
    ! Flutter version 3.7.0 on channel unknown at /Users/takashi/fvm/versions/pr
      Currently on an unknown channel. Run `flutter channel` to switch to an official channel.
      If that doesn't fix the issue, reinstall Flutter by following instructions at https://flutter.dev/docs/get-started/install.
    ! Warning: `dart` on your path resolves to /opt/homebrew/Cellar/dart/2.19.0/libexec/bin/dart, which is not inside your current Flutter SDK checkout at /Users/takashi/fvm/versions/pr. Consider adding /Users/takashi/fvm/versions/pr/bin to the front of your path.
    ! Unknown upstream repository.
      Reinstall Flutter by following instructions at https://flutter.dev/docs/get-started/install.
    • Framework revision b06b8b2710 (31 hours ago), 2023-01-23 16:55:55 -0800
    • Engine revision b24591ed32
    • Dart version 2.19.0
    • DevTools version 2.20.1
    • If those were intentional, you can disregard the above warnings; however it is recommended to use "git" directly to perform update checks and upgrades.

[✓] Android toolchain - develop for Android devices (Android SDK version 33.0.0)
    • Android SDK at /Users/takashi/Library/Android/sdk
    • Platform android-33, build-tools 33.0.0
    • Java binary at: /Applications/Android Studio.app/Contents/jre/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 11.0.13+0-b1751.21-8125866)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 14.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 14B47b
    • CocoaPods version 1.11.3

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2021.3)
    • 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 11.0.13+0-b1751.21-8125866)

[✓] VS Code (version 1.73.1)
    • VS Code at /Users/takashi/Downloads/Visual Studio Code.app/Contents
    • Flutter extension version 3.56.0

[✓] Connected device (3 available)
    • iPhone 11 Pro (mobile) • 5A465C61-E3D4-4FB1-B0E5-993F74D1219D • ios            • com.apple.CoreSimulator.SimRuntime.iOS-16-1 (simulator)
    • macOS (desktop)        • macos                                • darwin-arm64   • macOS 13.1 22C65 darwin-arm64
    • Chrome (web)           • chrome                               • web-javascript • Google Chrome 109.0.5414.87

[✓] HTTP Host Availability
    • All required HTTP hosts are available

! Doctor found issues in 1 category.
```

</details>


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I don't know a reason but when I set `appbar` in `Scaffold` it looks working...