import 'package:flutter/material.dart';
import 'package:flutter/rendering.dart';

void main() {
  debugPaintLayerBordersEnabled = true;
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      theme: ThemeData(sliderTheme: SliderThemeData(
        trackShape: RectangularSliderTrackShape(),
        trackHeight: 100
      )),
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  @override
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  double value = 0.5;
  _onChange(newValue) {
    setState(() {
      print('$newValue');
      value = newValue;
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        body: Directionality(
      textDirection: TextDirection.ltr,
      child: Center(
        child: RepaintBoundary(
          child: SizedBox(
            width: 500,
            height: 200,
            child: Slider(
              value: value,
              onChanged: _onChange,
            ),
          ),
        ),
      ),
    ));
  }
}