paintingStyle_stroke_web.dart

import 'package:flutter/material.dart';


void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) => MaterialApp(
        home: MyHomePage(),
      );
}

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

class _MyHomePageState extends State<MyHomePage> {
  @override
  void initState() {
    super.initState();
  }

  @override
  Widget build(BuildContext context) => Scaffold(
        body: CustomPaint(
          painter: AspectRatioPainter(
              isSelected: true, aspectRatio: 1.0, aspectRatioS: '1:1'),
        ),
      );
}

class AspectRatioPainter extends CustomPainter {
  final String aspectRatioS;
  final double aspectRatio;
  final bool isSelected;
  AspectRatioPainter(
      {this.aspectRatioS, this.aspectRatio, this.isSelected: false});

  @override
  void paint(Canvas canvas, Size size) {
    final Color color = isSelected ? Colors.blue : Colors.grey;
    var rect = (Offset.zero & size);
    print(rect);
    canvas.drawRect(
        rect,
        Paint()
          ..color = color
          ..style = PaintingStyle.stroke);
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) {
    var oldOne = oldDelegate as AspectRatioPainter;
    return oldOne.isSelected != isSelected ||
        oldOne.aspectRatioS != aspectRatioS ||
        oldOne.aspectRatio != aspectRatio;
  }
}