Flutter text painter

expandable_2.dart

class MyTextPainter extends CustomPainter {
  final TextSpan text;
  final int maxLines;
  final String ellipsis;

  MyTextPainter({this.text, this.ellipsis, this.maxLines}) : super();

  @override
  bool shouldRepaint(CustomPainter oldDelegate) => false;

  @override
  void paint(Canvas canvas, Size size) {
    TextPainter painter = TextPainter(
      text: text,
      maxLines: maxLines,
      textDirection: TextDirection.ltr,
    )..ellipsis = this.ellipsis;
    painter.layout(maxWidth: size.width);
    painter.paint(canvas, Offset(0, 0));
  }
}

class HomePage extends StatelessWidget {
  HomePage({Key key}) : super(key: key);

  var someVeryLongText = // Some realy long text

  @override
  Widget build(BuildContext context) => Scaffold(
        body: SafeArea(
          child: Container(
            child: CustomPaint(
              size: Size(double.infinity, 300),
              painter: MyTextPainter(
                text: TextSpan(text: someVeryLongText, style: TextStyle(color: Colors.black54)),
                ellipsis: "... more",
                maxLines: 4,
              ),
            ),
          ),
        ),
      );
}