More sendability improvements (please tell me this compiles on Windows)

Author: bbrk24

Sources/SwiftCrossUI/Environment/Actions/PresentAlertAction.swift

@@ -3,6 +3,7 @@
 /// selected action. By default, the alert will have a single button labelled
 /// `OK`. All buttons will dismiss the alert even if you provide your own
 /// actions.
+@MainActor
 public struct PresentAlertAction {
     let environment: EnvironmentValues
 

Sources/SwiftCrossUI/Environment/Actions/PresentFileSaveDialogAction.swift

@@ -2,9 +2,9 @@ import Foundation
 
 /// Presents a 'Save file' dialog fit for selecting a save destination. Returns
 /// `nil` if the user cancels the operation.
-public struct PresentFileSaveDialogAction {
+public struct PresentFileSaveDialogAction: Sendable {
     let backend: any AppBackend
-    let window: Any?
+    let window: MainActorBox<Any?>
 
     public func callAsFunction(
         title: String = "Save",
@@ -19,7 +19,7 @@ public struct PresentFileSaveDialogAction {
             return await withCheckedContinuation { continuation in
                 backend.runInMainThread {
                     let window: Backend.Window? =
-                        if let window = self.window {
+                        if let window = self.window.value {
                             .some(window as! Backend.Window)
                         } else {
                             nil

Sources/SwiftCrossUI/Environment/Actions/PresentSingleFileOpenDialogAction.swift

@@ -3,9 +3,9 @@ import Foundation
 /// Presents an 'Open file' dialog fit for selecting a single file. Some
 /// backends only allow selecting either files or directories but not both
 /// in a single dialog. Returns `nil` if the user cancels the operation.
-public struct PresentSingleFileOpenDialogAction {
+public struct PresentSingleFileOpenDialogAction: Sendable {
     let backend: any AppBackend
-    let window: Any?
+    let window: MainActorBox<Any?>
 
     public func callAsFunction(
         title: String = "Open",
@@ -20,7 +20,7 @@ public struct PresentSingleFileOpenDialogAction {
             await withCheckedContinuation { continuation in
                 backend.runInMainThread {
                     let window: Backend.Window? =
-                        if let window = self.window {
+                        if let window = self.window.value {
                             .some(window as! Backend.Window)
                         } else {
                             nil

Sources/SwiftCrossUI/Environment/EnvironmentValues.swift

@@ -97,10 +97,11 @@ public struct EnvironmentValues {
     /// accessed outside of a scene's view graph (in which case the backend
     /// can decide whether to make it an app modal, a standalone window, or a
     /// window of its choosing).
+    @MainActor
     public var chooseFile: PresentSingleFileOpenDialogAction {
         return PresentSingleFileOpenDialogAction(
             backend: backend,
-            window: window
+            window: .init(value: window)
         )
     }
 
@@ -110,17 +111,19 @@ public struct EnvironmentValues {
     /// scene's view graph (in which case the backend can decide whether to
     /// make it an app modal, a standalone window, or a modal for a window of
     /// its chooosing).
+    @MainActor
     public var chooseFileSaveDestination: PresentFileSaveDialogAction {
         return PresentFileSaveDialogAction(
             backend: backend,
-            window: window
+            window: .init(value: window)
         )
     }
 
     /// Presents an alert for the current window, or the entire app if accessed
     /// outside of a scene's view graph (in which case the backend can decide
     /// whether to make it an app modal, a standalone window, or a modal for a
     /// window of its choosing).
+    @MainActor
     public var presentAlert: PresentAlertAction {
         return PresentAlertAction(
             environment: self

Sources/SwiftCrossUI/Values/MainActorBox.swift

@@ -0,0 +1,4 @@
+@MainActor
+struct MainActorBox<T>: Sendable {
+    var value: T
+}

Sources/WinUIBackend/WinUIBackend.swift

@@ -55,11 +55,11 @@ public final class WinUIBackend: AppBackend {
         var sliderChangeActions: [ObjectIdentifier: (Double) -> Void] = [:]
         var textFieldChangeActions: [ObjectIdentifier: (String) -> Void] = [:]
         var textFieldSubmitActions: [ObjectIdentifier: () -> Void] = [:]
-        var dispatcherQueue: WinAppSDK.DispatcherQueue?
         var themeChangeAction: (() -> Void)?
     }
 
     private var internalState: InternalState
+    nonisolated(unsafe) private var dispatcherQueue: WinAppSDK.DispatcherQueue?
     /// WinUI only allows one dialog at a time (subsequent dialogs throw
     /// exceptions), so we limit ourselves.
     private var dialogSemaphore = DispatchSemaphore(value: 1)
@@ -128,8 +128,8 @@ public final class WinUIBackend: AppBackend {
             }
         }
 
-        if internalState.dispatcherQueue == nil {
-            internalState.dispatcherQueue = window.dispatcherQueue
+        if self.dispatcherQueue == nil {
+            self.dispatcherQueue = window.dispatcherQueue
         }
 
         // import WinSDK
@@ -238,7 +238,7 @@ public final class WinUIBackend: AppBackend {
     }
 
     public func runInMainThread(action: @escaping @MainActor () -> Void) {
-        _ = try! internalState.dispatcherQueue!.tryEnqueue(.normal) {
+        _ = try! dispatcherQueue!.tryEnqueue(.normal) {
             action()
         }
     }