Repository: flutter
Issue: `Slider` has a slight a lag when drag
Labels: framework,f: material design,a: fidelity,has reproducible steps,P2,found in release: 3.3,found in release: 3.7,team-design,triaged-design

1. It looks like the default slider widget in Flutter has a slight lag when being moved. It's definitely nothing terrible BUT slow enough to notice it doesn't feel native on iOS. Just check how iOS slider should behave by going e.g. to iPhone Settings->Screen and Brightness -> Change Brightness by sliding.

Sliding a native iOS slider is instant whereas sliding a Flutter slider is with a (slight) lag.

<details>
<summary>2. Code Sample </summary>

```
import 'package:flutter/material.dart';


void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        primarySwatch: Colors.blue,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);


  final String title;

  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  int height = 170;
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(widget.title),
      ),
      body: Center(
        child: Slider(
          min: 150.0,
          max: 180.0,
          value: height.toDouble(),
          divisions: 30,
          onChanged: (double newValue) {
            setState(() {
              height = newValue.toInt();
            });
          },
        ),
      ), // This trailing comma makes auto-formatting nicer for build methods.
    );
  }
}
```

</details>

3. https://photos.app.goo.gl/mcSbDNyoPJYwYrns8

## Details

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       flutter channel master
       flutter run --profile --trace-skia
     Then press ‘P’ to enable the performance overlay.

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**Target Platform:**
iOS
**Target OS version/browser:**
13.3.1
**Devices:**
iPhone XR
## Logs

<!--
     Run `flutter analyze` and attach any output of that command below.
     If there are any analysis errors, try resolving them before filing this issue.
-->
Analyzing flutter_app_slider_experiment...                              
No issues found! (ran in 2.2s)

<!-- Finally, paste the output of running `flutter doctor -v` here, with your device plugged in. -->

[✓] Flutter (Channel master, v1.15.4-pre.241, on Mac OS X 10.15.3 19D76, locale es-ES)
    • Flutter version 1.15.4-pre.241 at /Users/tomas/Developer/flutter
    • Framework revision 1d3fcfd6ca (5 hours ago), 2020-02-29 10:01:18 -0800
    • Engine revision 755e2b559d
    • Dart version 2.8.0 (build 2.8.0-dev.10.0 09bbd3cca5)

 
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
    • Android SDK at /Users/tomas/Library/Android/sdk
    • Android NDK location not configured (optional; useful for native profiling support)
    • Platform android-29, build-tools 29.0.3
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 11.3.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 11.3.1, Build version 11C504
    • CocoaPods version 1.8.4

[✓] Android Studio (version 3.5)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin version 43.0.1
    • Dart plugin version 191.8593
    • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b49-5587405)

[✓] Connected device (1 available)
    • iPhone • 00008020-000415840E50003A • ios • iOS 13.3.1

• No issues found!