Fix up concurrency warnings

.github/workflows/ci.yml

@@ -18,7 +18,7 @@ jobs:
     name: Test
     runs-on: macOS-14
     env:
-      DEVELOPER_DIR: /Applications/Xcode_15.3.app/Contents/Developer
+      DEVELOPER_DIR: /Applications/Xcode_15.4.app/Contents/Developer
     steps:
       - uses: actions/checkout@v4
         with:

Package.swift

@@ -1,16 +1,28 @@
-// swift-tools-version:5.0
+// swift-tools-version: 5.8
 
 import PackageDescription
 
 let package = Package(
-    name: "WindowTreatment",
-    platforms: [.macOS("10.11")],
-    products: [
-        .library(name: "WindowTreatment", targets: ["WindowTreatment"]),
-    ],
-    dependencies: [],
-    targets: [
-        .target(name: "WindowTreatment", dependencies: []),
-        .testTarget(name: "WindowTreatmentTests", dependencies: ["WindowTreatment"]),
-    ]
+	name: "WindowTreatment",
+	platforms: [
+		.macOS(.v10_13),
+	],
+	products: [
+		.library(name: "WindowTreatment", targets: ["WindowTreatment"]),
+	],
+	dependencies: [],
+	targets: [
+		.target(name: "WindowTreatment", dependencies: []),
+		.testTarget(name: "WindowTreatmentTests", dependencies: ["WindowTreatment"]),
+	]
 )
+
+let swiftSettings: [SwiftSetting] = [
+	.enableExperimentalFeature("StrictConcurrency"),
+]
+
+for target in package.targets {
+	var settings = target.swiftSettings ?? []
+	settings.append(contentsOf: swiftSettings)
+	target.swiftSettings = settings
+}

Sources/WindowTreatment/ApplicationWindowState.swift

@@ -8,6 +8,7 @@
 
 import Cocoa
 
+@MainActor
 public class ApplicationWindowState {
     private var lastWindowListHash: Int
     private var lastMainWindowHash: Int
@@ -39,7 +40,7 @@ public class ApplicationWindowState {
     @objc private func windowWillCloseNotification(_ notification: NSNotification) {
         // The reason for the async thing here is because this notification tells
         // you which window *will* close, but it is currently still in the current list.
-        OperationQueue.main.addOperation {
+		DispatchQueue.main.async {
             self.deliverChangeNotificationIfNeeded()
         }
     }

Sources/WindowTreatment/Modifiers/WindowStateObservingModifier.swift

@@ -1,6 +1,7 @@
 import SwiftUI
 
 @available(macOS 11.0, *)
+@MainActor
 final class WindowObserverModel: ObservableObject {
 	private let observer = WindowStateObserver()
 	@Published var windowState = WindowStateObserver.State(window: nil)

Sources/WindowTreatment/NSWindow+Animation.swift

@@ -9,14 +9,14 @@
 import Cocoa
 
 extension NSWindow {
-    public func withAnimationDisabled(block: () -> Void) {
+    public func withAnimationDisabled(block: @MainActor () -> Void) {
         let currentBehavior = animationBehavior
 
         animationBehavior = .none
 
         block()
 
-        OperationQueue.main.addOperation {
+		DispatchQueue.main.async {
             self.animationBehavior = currentBehavior
         }
     }

Sources/WindowTreatment/WindowStateObserver.swift

@@ -1,43 +1,48 @@
 import Cocoa
 
 extension NSWindow {
-    static var tabStateDidChangeNotification = Notification.Name("windowTabStateDidChangeNotification")
+    static let tabStateDidChangeNotification = Notification.Name("windowTabStateDidChangeNotification")
 }
 
+@MainActor
 public final class WindowStateObserver {
-    public struct State: Hashable {
-        public var isMain: Bool
-        public var isKey: Bool
-        public var tabBarVisible: Bool
-        public var tabCount: Int
-
-        public init(window: NSWindow?) {
-            self.isMain = window?.isMainWindow ?? false
-            self.isKey = window?.isKeyWindow ?? false
-
-            // use of this property is essential
-            self.tabBarVisible = window?.isTabBarVisible ?? false
-
-            if #available(macOS 10.12, *) {
-                self.tabCount = window?.tabbedWindows?.count ?? 0
-            } else {
-                self.tabCount = 0
-            }
-        }
-
-        public var isKeyOrMain: Bool {
-            return isMain || isKey
-        }
-
-        public var tabbed: Bool {
-            return tabBarVisible && tabCount > 1
-        }
-
-        public func tabStateEqual(to other: State) -> Bool {
-            return tabBarVisible == other.tabBarVisible && tabCount == other.tabCount
-        }
-    }
-
+	public struct State: Hashable, Sendable {
+		public var isMain: Bool
+		public var isKey: Bool
+		public var tabBarVisible: Bool
+		public var tabCount: Int
+
+		@MainActor
+		public init(window: NSWindow?) {
+			self.isMain = window?.isMainWindow ?? false
+			self.isKey = window?.isKeyWindow ?? false
+
+			// use of this property is essential
+			self.tabBarVisible = window?.isTabBarVisible ?? false
+
+			self.tabCount = window?.tabbedWindows?.count ?? 0
+		}
+
+		public init() {
+			self.isMain = false
+			self.isKey = false
+			self.tabBarVisible = false
+			self.tabCount = 0
+		}
+
+		public nonisolated var isKeyOrMain: Bool {
+			return isMain || isKey
+		}
+
+		public nonisolated var tabbed: Bool {
+			return tabBarVisible && tabCount > 1
+		}
+
+		public nonisolated func tabStateEqual(to other: State) -> Bool {
+			return tabBarVisible == other.tabBarVisible && tabCount == other.tabCount
+		}
+	}
+
     public typealias ObserverBlock = (State, State) -> Void
 
     public var block: ObserverBlock?
@@ -56,10 +61,6 @@ public final class WindowStateObserver {
         self.block = block
     }
 
-    deinit {
-        deregisterForWindowNotifications()
-    }
-
     private func registerForWindowNotifications(_ window: NSWindow) {
         if (window.canBecomeKey || window.canBecomeMain) == false {
             print("Warning: WindowStateObserver is monitoring a window that cannot become key or main")
@@ -97,7 +98,9 @@ public final class WindowStateObserver {
         // While this API is actually available in 10.12, observing this will reliably cause crashes in 10.14...
         if #available(macOS 10.15, *) {
             self.tabbedWindowsObservation = window.observe(\.tabbedWindows, options: [], changeHandler: { [unowned self] (obj, _) in
-                self.handlePossibleStateChange(for: obj, forward: true)
+				MainActor.assumeIsolated {
+					self.handlePossibleStateChange(for: obj, forward: true)
+				}
             })
         }
     }

Sources/WindowTreatment/WindowStateObservingView.swift

@@ -3,8 +3,7 @@ import SwiftUI
 
 @available(macOS 10.15, *)
 public struct WindowStateKey: EnvironmentKey {
-    public typealias Value = WindowStateObserver.State
-    public static var defaultValue: Value = .init(window: nil)
+    public static let defaultValue: WindowStateObserver.State = .init()
 }
 
 @available(macOS 10.15, *)

Tests/WindowTreatmentTests/WindowTitlebarAwareViewTests.swift

@@ -9,7 +9,8 @@
 import XCTest
 @testable import WindowTreatment
 
-class WindowTitlebarAwareViewTests: XCTestCase {
+final class WindowTitlebarAwareViewTests: XCTestCase {
+	@MainActor
     func testCreateViewInWindowWithVisibleTitlebar() {
         let view = WindowTitlebarAwareView()
         let contentView = NSView()
@@ -27,6 +28,7 @@ class WindowTitlebarAwareViewTests: XCTestCase {
         XCTAssertEqual(contentView.frame, window.contentLayoutRect)
     }
 
+	@MainActor
     func testCreateViewInWindowWithInvisibleTitlebar() {
         let view = WindowTitlebarAwareView()
         let contentView = NSView()