Flutter customPainter doesn't repaint - flutter

Question

shouldRepaint doesn't repaint when there is a change:
import 'package:flutter/material.dart';
class MainCanvas extends CustomPainter{
static var penPointsToRender = [];
#override
void paint(Canvas canvas, Size size) {
Paint paint = Paint()..color=Colors.black..strokeWidth=4;
renderPenPoints(paint, canvas, 2);
}
static void renderPenPoints(Paint paint, Canvas canvas, double pointsRadius){
for (int i = 0; i < penPointsToRender.length - 1; i++) {
if (penPointsToRender[i + 1] != null && penPointsToRender[i] != null) {
canvas.drawLine(penPointsToRender[i], penPointsToRender[i + 1], paint);
}
}
}
#override
bool shouldRepaint(covariant CustomPainter oldDelegate) {
return true;
}
}
this list get's updated on every touch.
I have this custom gesture detector that uses a provider as it's state management system:
import 'package:flutter/material.dart';
import 'package:flutter_canvas/Widgets/Models/canvas_gesture_detector_model.dart';
class CanvasGestureDetector extends StatefulWidget {
CanvasGestureDetector(this.canvasGestureDetectorModel,{Key key,this.child}) : super(key: key);
CanvasGestureDetectorModel canvasGestureDetectorModel;
Widget child;
#override
_CanvasGestureDetectorState createState() => _CanvasGestureDetectorState();
}
class _CanvasGestureDetectorState extends State<CanvasGestureDetector> {
#override
Widget build(BuildContext context) {
return GestureDetector(
behavior: HitTestBehavior.translucent,
onPanDown: widget.canvasGestureDetectorModel.onPanDown,
onPanUpdate: widget.canvasGestureDetectorModel.onPanUpdate,
onPanEnd: widget.canvasGestureDetectorModel.onPanEnd,
child: widget.child,
);
}
}
the model of the detector is:
import 'package:flutter/material.dart';
import 'package:flutter_canvas/Widgets/Canvas/canvas.dart';
import 'package:flutter_canvas/Widgets/Canvas/canvas_area.dart';
class CanvasGestureDetectorModel with ChangeNotifier{
Function(DragDownDetails) onPanDown;
Function(DragUpdateDetails) onPanUpdate;
Function(DragEndDetails) onPanEnd;
void changeGestureBehavior(BuildContext context,String toolName){
switch(toolName){
case "Brush":
setBrushGestureDetection(context);
break;
}
}
void setBrushGestureDetection(BuildContext context){
onPanDown = (panInfo){
MainCanvas.penPointsToRender.add(panInfo.localPosition);
};
onPanUpdate = (panInfo){
if(
panInfo.globalPosition.dx < CanvasArea.canvasPaddingHorizontal / 2 ||
panInfo.globalPosition.dx > CanvasArea.canvasPaddingHorizontal / 2 + (MediaQuery.of(context).size.width - CanvasArea.canvasPaddingHorizontal) ||
panInfo.globalPosition.dy < CanvasArea.canvasPaddingVertical / 2 - 20 ||
panInfo.globalPosition.dy > (MediaQuery.of(context).size.height - CanvasArea.canvasPaddingVertical) + (CanvasArea.canvasPaddingVertical ) / 2 -20
){return;}
if (MainCanvas.penPointsToRender.elementAt(
MainCanvas.penPointsToRender.length - 1) != panInfo.localPosition) {
MainCanvas.penPointsToRender.add(panInfo.localPosition);
}
};
onPanEnd = (panInfo){
MainCanvas.penPointsToRender.add(null);
};
notifyListeners();
}
}
from some reason,
when I update the number of penPointsToRender it doesn't cause the customPainter to repaint, even though it updates and adds the points to the static list.
I have no idea what causes this, any suggestions would be appreciated