Snapping Behavior Custom ScrollPhysics - flutter

Question

After some tinkering and Googling all over the place I became super frustrated with the API / lack of documentation for ScrollPhysics.
On Android you can use what's called a SnapHelper inside your RecyclerView (analogous to a ListView in Flutter) that will automatically snap to a certain position.
The SnapHelper does this on a position based API.
You can ask which View is currently in your chosen ViewPort and get its position and ask the RecyclerView to animate to that position.
Flutter on the other hand wants us to work with logical pixels, which makes this super trivial, common pattern difficult to implement.
All the solutions I found was to use items inside the list that have a fixed width/height and don't account for flinging gestures.
tl;dr How to implement this 👆in Flutter so it works for any item in a ListView?
I'm including the poor mans version we are currently using.
Which works, but not like we are used to on Android.
Especially passing the itemWidth is an eyesore
class SnappingListScrollPhysics extends ScrollPhysics {
final double itemWidth;
const SnappingListScrollPhysics({
#required this.itemWidth,
ScrollPhysics parent,
}) : super(parent: parent);
#override
SnappingListScrollPhysics applyTo(ScrollPhysics ancestor) => SnappingListScrollPhysics(
parent: buildParent(ancestor),
itemWidth: itemWidth,
);
double _getItem(ScrollPosition position) => (position.pixels) / itemWidth;
double _getPixels(ScrollPosition position, double item) => min(item * itemWidth, position.maxScrollExtent);
double _getTargetPixels(ScrollPosition position, Tolerance tolerance, double velocity) {
double item = _getItem(position);
if (velocity < -tolerance.velocity) {
item -= 0.5;
} else if (velocity > tolerance.velocity) {
item += 0.5;
}
return _getPixels(position, item.roundToDouble());
}
#override
Simulation createBallisticSimulation(ScrollMetrics position, double velocity) {
// If we're out of range and not headed back in range, defer to the parent
// ballistics, which should put us back in range at a page boundary.
if ((velocity <= 0.0 && position.pixels <= position.minScrollExtent) ||
(velocity >= 0.0 && position.pixels >= position.maxScrollExtent)) {
return super.createBallisticSimulation(position, velocity);
}
final Tolerance tolerance = this.tolerance;
final double target = _getTargetPixels(position, tolerance, velocity);
if (target != position.pixels) {
return ScrollSpringSimulation(spring, position.pixels, target, velocity, tolerance: tolerance);
}
return null;
}
#override
bool get allowImplicitScrolling => false;
}