Swift 6 strict-concurrency fixes and Dart-owned annotation image pixel ratio

darwin/mapkit_flutter/Sources/mapkit_flutter/Annotations/AnnotationIcon.swift

@@ -44,7 +44,8 @@ class AnnotationIcon: Equatable {
         case .image:
             self.iconType = .image
             if let data = icon.imageBytes?.data {
-                self.image = PlatformImage.fromImageData(data)
+                self.image = PlatformImage.fromImageData(
+                    data, pixelRatio: CGFloat(icon.imagePixelRatio ?? 1))
             }
         }
     }

darwin/mapkit_flutter/Sources/mapkit_flutter/MapKitPlugin.swift

@@ -15,6 +15,9 @@ public final class MapKitPlugin: NSObject, FlutterPlugin {
         // Plugin registration runs on the main thread; the factory and view
         // host are main-actor isolated. macOS's GeneratedPluginRegistrant
         // calls this from a nonisolated context, so assume isolation here.
+        // The registrar hand-off shares that guarantee: it never leaves the
+        // main thread, it just isn't Sendable-provable.
+        nonisolated(unsafe) let registrar = registrar
         MainActor.assumeIsolated {
             let factory = MapKitViewFactory(withRegistrar: registrar)
             #if os(iOS)

darwin/mapkit_flutter/Sources/mapkit_flutter/MapView/FlutterMapView.swift

@@ -10,7 +10,10 @@ import AppKit
 import FlutterMacOS
 #endif
 
-class FlutterMapView: MKMapView, PlatformGestureRecognizerDelegate, CLLocationManagerDelegate {
+// `@preconcurrency`: CLLocationManagerDelegate is nonisolated, but callbacks
+// arrive on the thread that created the manager — main, since the manager is
+// an instance property of this MainActor-isolated view.
+class FlutterMapView: MKMapView, PlatformGestureRecognizerDelegate, @preconcurrency CLLocationManagerDelegate {
     weak var flutterApi: MapKitFlutterApi?
 
     /// Camera handed over before the first layout pass; re-applied once the

darwin/mapkit_flutter/Sources/mapkit_flutter/MapView/MapKitViewHost.swift

@@ -297,7 +297,12 @@ extension MapKitViewHost {
         snapshotOptions.region = self.mapView.region
         snapshotOptions.size = self.mapView.frame.size
         #if os(iOS)
-        snapshotOptions.scale = PlatformScreen.scale
+        // Unspecified traits report displayScale == 0; leaving `scale` unset
+        // falls back to MapKit's main-screen default.
+        let displayScale = self.mapView.traitCollection.displayScale
+        if displayScale > 0 {
+            snapshotOptions.scale = displayScale
+        }
         #endif
         snapshotOptions.showsBuildings = options.showsBuildings
         snapshotOptions.pointOfInterestFilter = options.showsPointsOfInterest ? .includingAll : .excludingAll
@@ -367,7 +372,10 @@ extension MapKitViewHost {
 }
 
 #if os(iOS)
-extension MapKitViewHost: FlutterPlatformView {
+// `@preconcurrency`: FlutterPlatformView is nonisolated; the engine calls
+// `view()` on the platform thread (main), same as the MapKitHostApi
+// conformance above.
+extension MapKitViewHost: @preconcurrency FlutterPlatformView {
     public func view() -> UIView {
         return contentView
     }

darwin/mapkit_flutter/Sources/mapkit_flutter/Overlays/FlutterPolyline.swift

@@ -161,6 +161,7 @@ final class FlutterGeodesicPolyline: MKGeodesicPolyline, StyledPolyline, @unchec
 
 public extension MKPolyline {
     // maxMeters is the preferred distance offset from the self to be acknowledged as a touch
+    @MainActor
     func contains(coordinate: CLLocationCoordinate2D, mapView: MKMapView, maxMeters: Int = 8) -> Bool {
         let distance: Double = distanceOf(pt: MKMapPoint.init(coordinate), toMultipPoint: self)
         return distance <= meters(fromPixel: maxMeters, at: coordinate, view: mapView)
@@ -200,6 +201,7 @@ public extension MKPolyline {
         return distance
     }
 
+    @MainActor
     private func meters(fromPixel pixel: Int, at touchCoordinate: CLLocationCoordinate2D, view: MKMapView) -> Double {
         let touchPoint: CGPoint = view.convert(touchCoordinate, toPointTo: view)
         let maxOffsetPoint = CGPoint(x: touchPoint.x + CGFloat(pixel), y: touchPoint.y)

darwin/mapkit_flutter/Sources/mapkit_flutter/Utils/PlatformAliases.swift

@@ -42,18 +42,6 @@ extension PlatformView {
     }
 }
 
-enum PlatformScreen {
-    /// Backing scale factor of the main screen (`UIScreen.scale` /
-    /// `NSScreen.backingScaleFactor`). Defaults to 2 when unavailable.
-    static var scale: CGFloat {
-        #if os(iOS)
-        return UIScreen.main.scale
-        #elseif os(macOS)
-        return NSScreen.main?.backingScaleFactor ?? 2
-        #endif
-    }
-}
-
 extension PlatformImage {
     /// An SF Symbol image by name (`UIImage(systemName:)` /
     /// `NSImage(systemSymbolName:)`).
@@ -65,19 +53,18 @@ extension PlatformImage {
         #endif
     }
 
-    /// A bitmap image from raw PNG/image bytes, sized in points to match the
-    /// screen scale (`UIImage(data:scale:)` has no AppKit equivalent, so the
-    /// macOS path divides the pixel size by the backing scale).
-    static func fromImageData(_ data: Data) -> PlatformImage? {
+    /// A bitmap image from raw PNG/image bytes, sized in points via the
+    /// Dart-supplied pixel ratio of the bytes (`UIImage(data:scale:)` has no
+    /// AppKit equivalent, so the macOS path divides the pixel size by it).
+    static func fromImageData(_ data: Data, pixelRatio: CGFloat) -> PlatformImage? {
         #if os(iOS)
-        return UIImage(data: data, scale: PlatformScreen.scale)
+        return UIImage(data: data, scale: pixelRatio)
         #elseif os(macOS)
         guard let image = NSImage(data: data) else { return nil }
         if let rep = image.representations.first {
-            let scale = PlatformScreen.scale
             image.size = NSSize(
-                width: CGFloat(rep.pixelsWide) / scale,
-                height: CGFloat(rep.pixelsHigh) / scale
+                width: CGFloat(rep.pixelsWide) / pixelRatio,
+                height: CGFloat(rep.pixelsHigh) / pixelRatio
             )
         }
         return image