Mac-specific fixes

Author: bbrk24

Sources/SwiftCrossUI/Backend/AppBackend.swift

@@ -41,7 +41,7 @@ import Foundation
 /// (since the `update` method is always called between calling `create`
 /// and actually displaying the widget anyway).
 @MainActor
-public protocol AppBackend {
+public protocol AppBackend: Sendable {
     associatedtype Window
     associatedtype Widget
     associatedtype Menu

Sources/SwiftCrossUI/Environment/Actions/OpenURLAction.swift

@@ -2,8 +2,9 @@ import Foundation
 
 /// Opens a URL with the default application. May present an application picker
 /// if multiple applications are registered for the given URL protocol.
+@MainActor
 public struct OpenURLAction {
-    let action: @MainActor (URL) -> Void
+    let action: (URL) -> Void
 
     init<Backend: AppBackend>(backend: Backend) {
         action = { url in
@@ -15,7 +16,6 @@ public struct OpenURLAction {
         }
     }
 
-    @MainActor
     public func callAsFunction(_ url: URL) {
         action(url)
     }

Sources/SwiftCrossUI/Environment/EnvironmentValues.swift

@@ -130,6 +130,7 @@ public struct EnvironmentValues {
     /// Opens a URL with the default application. May present an application
     /// picker if multiple applications are registered for the given URL
     /// protocol.
+    @MainActor
     public var openURL: OpenURLAction {
         return OpenURLAction(
             backend: backend

Sources/UIKitBackend/KeyboardToolbar.swift

@@ -14,9 +14,11 @@ public protocol ToolbarItem {
     associatedtype ItemType: UIBarButtonItem
 
     /// Convert the item to an instance of `ItemType`.
+    @MainActor
     func createBarButtonItem() -> ItemType
 
     /// Update the item with new information (e.g. updated bindings). May be a no-op.
+    @MainActor
     func updateBarButtonItem(_ item: inout ItemType)
 }
 
@@ -61,9 +63,9 @@ public enum ToolbarBuilder {
 @available(tvOS, unavailable)
 extension Button: ToolbarItem {
     public final class ItemType: UIBarButtonItem {
-        var callback: () -> Void
+        var callback: @MainActor @Sendable () -> Void
 
-        init(title: String, callback: @escaping () -> Void) {
+        init(title: String, callback: @escaping @MainActor @Sendable () -> Void) {
             self.callback = callback
             super.init()
 

Tests/SwiftCrossUITests/SwiftCrossUITests.swift

@@ -65,7 +65,8 @@ final class SwiftCrossUITests: XCTestCase {
     }
 
     #if canImport(AppKitBackend)
-        func testBasicLayout() throws {
+        @MainActor
+        func testBasicLayout() async throws {
             let backend = AppKitBackend()
             let window = backend.createWindow(withDefaultSize: SIMD2(200, 200))
 
@@ -104,6 +105,7 @@ final class SwiftCrossUITests: XCTestCase {
             )
         }
 
+        @MainActor
         static func snapshotView(_ view: NSView) throws -> Data {
             view.wantsLayer = true
             view.layer?.backgroundColor = CGColor.white