import 'dart:ui' as ui;

import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class Painter extends CustomPainter {
  Painter(this.scale, this.textSize);

  double scale = 1;
  double textSize = 1;

  @override
  void paint(Canvas canvas, Size size) {
    debugPrint("Scale: $scale  FontSize: $textSize");

    ui.ParagraphBuilder b = ui.ParagraphBuilder(
        ui.ParagraphStyle(fontSize: textSize, fontStyle: FontStyle.normal))
      ..pushStyle(ui.TextStyle(color: Colors.black))
      ..addText("i");
    ui.Paragraph p = b.build();
    p.layout(ui.ParagraphConstraints(width: size.width));

    canvas.scale(scale);
    canvas.drawParagraph(p, const Offset(0, 0));
  }

  @override
  bool shouldRepaint(covariant CustomPainter oldDelegate) {
    return true;
  }
}

class MyApp extends StatefulWidget {
  const MyApp({super.key});

  @override
  State<MyApp> createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {
  double scale = 1;
  double textSize = 10;

  @override
  Widget build(BuildContext context) => MaterialApp(
        debugShowCheckedModeBanner: false,
        home: Scaffold(
          body: Flex(
            direction: Axis.vertical,
            children: [
              const SizedBox.square(dimension: 50),
              Slider(
                  min: 0,
                  max: 10,
                  value: scale,
                  onChanged: (double value) {
                    setState(() {
                      scale = value;
                    });
                  }),
              Slider(
                  min: 0,
                  max: 50,
                  value: textSize,
                  onChanged: (double value) {
                    setState(() {
                      textSize = value;
                    });
                  }),
              Expanded(child: CustomPaint(painter: Painter(scale, textSize))),
            ],
          ),
        ),
      );
}