How to reset the matrix

[meDerekD17]

Using info from Resetting the Matrix#8, I got the matrix to reset correcting when using CustomPaint (basically the same code as the example with CustomPaint). But I have no idea why it is working. I seem to have replaced notifier.value = m, with notifier.value = matrix; when normal zoom, offset and rotation.

It seems to work, but I do not understand. Is it possible my code will give memory leaks or anything? Is it the best way for CustomPaint?

My Code:
class _CustomPainterDemoState extends State {
Matrix4 matrix = Matrix4.identity();
ValueNotifier notifier;
bool resetMatrix = false;

@OverRide
void initState() {
super.initState();
notifier = ValueNotifier(matrix);
.....
in the build
body: MatrixGestureDetector(
onMatrixUpdate: (m, tm, sm, rm) {
if(resetMatrix) {
matrix = MatrixGestureDetector.compose(matrix, tm, sm, rm);
//above appears to reset all matrices
}
notifier.value = matrix; //original code had notifier.value = m
},

I then have child: CustomPaint, exactly like the example
At the bottom, I have a floating Action Button to reset the screen
floatingActionButton: FloatingActionButton(
onPressed:(){
setState(() {
matrix = Matrix4.identity();
notifier = ValueNotifier(matrix);
resetMatrix = true;
});
}
),

[JoseGeorges8]

This works for me:

onMatrixUpdate: (Matrix4 m, Matrix4 tm, Matrix4 sm, Matrix4 rm) {
    setState(() {
        matrix = MatrixGestureDetector.compose(matrix, tm, sm, rm);
    });
},

And arround MatrixGestureDetector I've got a gesture detector like so:

GestureDetector(
    onDoubleTap: (){
        setState(() {
            matrix = Matrix4.identity();
         });
     },
     child: MatrixGestureDetector(...),
);