setState not really settng the state [flutter] - flutter

Question

So I have this code that is supposed to draw to the canvas.
import 'dart:ui';
import 'package:flutter/material.dart';
void main() {
runApp(const MyApp());
}
class MyApp extends StatelessWidget {
const MyApp({Key? key}) : super(key: key);
#override
Widget build(BuildContext context) {
return const MaterialApp(
debugShowCheckedModeBanner: false,
home: Home(),
);
}
}
// offsets
List<Offset?> offsets = [];
class Home extends StatefulWidget {
const Home({
Key? key,
}) : super(key: key);
#override
State<Home> createState() => _HomeState();
}
class _HomeState extends State<Home> {
// offsets
List<Offset?> offsets = [];
#override
Widget build(BuildContext context) {
return Scaffold(
appBar: AppBar(
title: const Text('Drawing'),
),
body: GestureDetector(
onPanDown: (details) {
setState(() {
offsets.add(details.localPosition);
});
},
onPanUpdate: (details) {
setState(() {
offsets.add(details.localPosition);
});
},
onPanEnd: (details) {
setState(() {
offsets.add(null);
});
},
child: Container(
width: double.infinity,
height: MediaQuery.of(context).size.height,
color: Colors.grey,
child: CustomPaint(
foregroundPainter: Painter(offsets: offsets),
),
),
),
);
}
}
class Painter extends CustomPainter {
Painter({required this.offsets});
List<Offset?> offsets;
#override
void paint(Canvas canvas, Size size) {
Paint paint = Paint()
..strokeWidth = 2
..style = PaintingStyle.stroke;
// for every offset and the next offset
for (int i = 0; i < offsets.length - 1; i++) {
// if both are not null
if (offsets[i] != null && offsets[i + 1] != null) {
canvas.drawLine(offsets[i]!, offsets[i + 1]!, paint);
} else if (offsets[i] != null && offsets[i + 1] == null) {
canvas.drawPoints(PointMode.points, [offsets[i]!], paint);
}
}
print('paint called');
}
#override
bool shouldRepaint(covariant CustomPainter oldDelegate) {
return false;
}
}
How this is working is that it detects the gestures on the container and when there is a swipe on the container, it records the offsets of that and adds them to the offsets array. Later that array is being passed to the custom painter where we go through all the offsets and render the lines. So when I add the offsets to the array I use setState so that the new offsets are added, the screen is rendered again, new offsets are passed to the custom painter and it renders those lines. But it's not working when I make a swipe but the lines appear when I make a hot reload. Why is this? Why I need to manually hot reload to see those lines? Any help will be appreciated.
Edit: It seems like the offsets are being added properly and the setState is also working fine but somehow the custom painter is not being called.

Answer 1

NVM, returning true from shouldRepaint method solve the issue.
#override
bool shouldRepaint(covariant CustomPainter oldDelegate) {
return true;
}