SwiftUI PencilKit Coordinator for navigation - swiftui

Question

Rather than selecting from a list, I'm trying to navigate between drawings like a book by using buttons to cycle through, but the canvas doesn't update.
I'm following the great tutorial by DevTechie at https://www.youtube.com/watch?v=amZH2i6l004&list=PLbrKvTeCrFAfoACvHOPWFmDIaKUqBZgEr&index=5
The github repo is at https://github.com/devtechie/DrawingDocuments
Here's my ContentView and my version of the DrawingWrapper. The DrawingWrapper uses a DrawingManager (SwiftUI) to pull from CoreData and the DrawingViewController to define a PKCanvas. I wasn't sure which delegate to use and really struggling understanding how to refresh the canvas.
ContentView
struct ContentView: View {
#StateObject var manager = DrawingManager()
#State var addNewShown = false
#State var pageNumber: Int = 0
#State var newVar = UUID()
var body: some View {
VStack{
Text(manager.docs[pageNumber].name!)
HStack{
Button(action:{
pageNumber -= 1
newVar = manager.docs[pageNumber].id!
//desiredDoc = manager.docs[pageNumber]
}){
Image(systemName: "chevron.left")
}
Spacer()
Button(action:{
pageNumber += 1
newVar = manager.docs[pageNumber].id!
//desiredDoc = manager.docs[pageNumber]
}){
Image(systemName: "chevron.right")
}
}
}
}
DrawingWrapper
struct DrawingWrapper: UIViewControllerRepresentable {
var manager: DrawingManager
#Binding var doc: DrawingDoc
typealias UIViewControllerType = DrawingViewController
class Coordinator: NSObject, PKCanvasViewDelegate {
var parent: DrawingWrapper
init(_ parent: DrawingWrapper){
self.parent = parent
}
func canvasViewDidFinishRendering(_ canvasView: PKCanvasView) {
if let uiDrawing = canvasView.drawing as? PKDrawing {
parent.doc.data = uiDrawing.dataRepresentation()
}
}
}
func makeCoordinator() -> Coordinator {
Coordinator(self)
}
func makeUIViewController(context: UIViewControllerRepresentableContext<DrawingWrapper>) -> DrawingWrapper.UIViewControllerType {
let viewController = DrawingViewController()
viewController.drawingData = doc.data!
viewController.drawingChanged = {data in
manager.update(data: data, for: doc.id!)
}
viewController.delegate = context.coordinator
return viewController
}
func updateUIViewController(_ uiViewController: DrawingViewController, context: UIViewControllerRepresentableContext<DrawingWrapper>) {
uiViewController.drawingData = doc.data!
}
}