MapViewPort implementation to listen to raw values of 'camera'

Sources/MapLibreSwiftUI/MapView.swift

@@ -11,6 +11,7 @@ public struct MapView: UIViewRepresentable {
 
     var gestures = [MapGesture]()
     var onStyleLoaded: ((MLNStyle) -> Void)?
+    var onViewPortChanged: ((MapViewPort) -> Void)?
 
     public var mapViewContentInset: UIEdgeInsets = .zero
     public var isLogoViewHidden = false
@@ -42,7 +43,8 @@ public struct MapView: UIViewRepresentable {
     public func makeCoordinator() -> MapViewCoordinator {
         MapViewCoordinator(
             parent: self,
-            onGesture: { processGesture($0, $1) }
+            onGesture: { processGesture($0, $1) },
+            onViewPortChanged: { onViewPortChanged?($0) }
         )
     }
 

Sources/MapLibreSwiftUI/MapViewCoordinator.swift

@@ -19,12 +19,15 @@ public class MapViewCoordinator: NSObject {
 
     var onStyleLoaded: ((MLNStyle) -> Void)?
     var onGesture: (MLNMapView, UIGestureRecognizer) -> Void
+    var onViewPortChanged: (MapViewPort) -> Void
 
     init(parent: MapView,
-         onGesture: @escaping (MLNMapView, UIGestureRecognizer) -> Void)
+         onGesture: @escaping (MLNMapView, UIGestureRecognizer) -> Void,
+         onViewPortChanged: @escaping (MapViewPort) -> Void)
     {
         self.parent = parent
         self.onGesture = onGesture
+        self.onViewPortChanged = onViewPortChanged
     }
 
     // MARK: Core UIView Functionality
@@ -205,6 +208,8 @@ extension MapViewCoordinator: MLNMapViewDelegate {
         onStyleLoaded?(mglStyle)
     }
 
+    // MARK: MapViewCamera
+
     @MainActor private func updateParentCamera(mapView: MLNMapView, reason: MLNCameraChangeReason) {
         // If any of these are a mismatch, we know the camera is no longer following a desired method, so we should
         // detach and revert to a .centered camera. If any one of these is true, the desired camera state still
@@ -247,6 +252,12 @@ extension MapViewCoordinator: MLNMapViewDelegate {
 
     /// The MapView's region has changed with a specific reason.
     public func mapView(_ mapView: MLNMapView, regionDidChangeWith reason: MLNCameraChangeReason, animated _: Bool) {
+        // FIXME: CI complains about MainActor.assumeIsolated being unavailable before iOS 17, despite building on iOS 17.2... This is an epic hack to fix it for now. I can only assume this is an issue with Xcode pre-15.3
+        // TODO: We could put this in regionIsChangingWith if we calculate significant change/debounce.
+        Task { @MainActor in
+            updateViewPort(mapView: mapView)
+        }
+
         guard !suppressCameraUpdatePropagation else {
             return
         }
@@ -256,4 +267,17 @@ extension MapViewCoordinator: MLNMapViewDelegate {
             updateParentCamera(mapView: mapView, reason: reason)
         }
     }
+
+    // MARK: MapViewPort
+
+    @MainActor private func updateViewPort(mapView: MLNMapView) {
+        // Calculate the Raw "ViewPort"
+        let calculatedViewPort = MapViewPort(
+            center: mapView.centerCoordinate,
+            zoom: mapView.zoomLevel,
+            direction: mapView.direction
+        )
+
+        onViewPortChanged(calculatedViewPort)
+    }
 }

Sources/MapLibreSwiftUI/MapViewModifiers.swift

@@ -99,4 +99,10 @@ public extension MapView {
 
         return result
     }
+
+    func onMapViewPortUpdate(_ onViewPortChanged: @escaping (MapViewPort) -> Void) -> Self {
+        var result = self
+        result.onViewPortChanged = onViewPortChanged
+        return result
+    }
 }

Sources/MapLibreSwiftUI/Models/MapViewPort.swift

@@ -0,0 +1,41 @@
+import CoreLocation
+import Foundation
+
+/// A representation of the MapView's current ViewPort.
+///
+/// This includes similar data to the MapViewCamera, but represents the raw
+/// values associated with the MapView. This information could used to prepare
+/// a new MapViewCamera on a scene, to cache the camera state, etc.
+public struct MapViewPort: Hashable, Equatable {
+    /// The current center coordinate of the MapView
+    public let center: CLLocationCoordinate2D
+
+    /// The current zoom value of the MapView
+    public let zoom: Double
+
+    /// The current compass direction of the MapView
+    public let direction: CLLocationDirection
+
+    public init(center: CLLocationCoordinate2D, zoom: Double, direction: CLLocationDirection) {
+        self.center = center
+        self.zoom = zoom
+        self.direction = direction
+    }
+
+    public static func zero(zoom: Double = 10) -> MapViewPort {
+        MapViewPort(center: CLLocationCoordinate2D(latitude: 0, longitude: 0),
+                    zoom: zoom,
+                    direction: 0)
+    }
+}
+
+public extension MapViewPort {
+    /// Generate a basic MapViewCamera that represents the MapViewPort
+    ///
+    /// - Returns: The calculated MapViewCamera
+    func asMapViewCamera() -> MapViewCamera {
+        .center(center,
+                zoom: zoom,
+                direction: direction)
+    }
+}

Tests/MapLibreSwiftUITests/MapViewCoordinator/MapViewCoordinatorCameraTests.swift

@@ -13,6 +13,8 @@ final class MapViewCoordinatorCameraTests: XCTestCase {
         mapView = MapView(styleURL: URL(string: "https://maplibre.org")!)
         coordinator = MapView.Coordinator(parent: mapView) { _, _ in
             // No action
+        } onViewPortChanged: { _ in
+            // No action
         }
     }