Allow Toggle in menus

Examples/Sources/WindowingExample/WindowingApp.swift

@@ -162,6 +162,7 @@ struct SheetDemo: View {
 struct WindowingApp: App {
     @State var title = "My window"
     @State var resizable = false
+    @State var toggle = false
 
     var body: some Scene {
         WindowGroup(title) {
@@ -204,6 +205,8 @@ struct WindowingApp: App {
             CommandMenu("Demo menu") {
                 Button("Menu item") {}
 
+                Toggle("Toggle", active: $toggle)
+
                 Menu("Submenu") {
                     Button("Item 1") {}
                     Button("Item 2") {}

Sources/AppKitBackend/AppKitBackend.swift

@@ -166,6 +166,25 @@ public final class AppKitBackend: AppBackend {
                         renderedItem.action = #selector(wrappedAction.run)
                         renderedItem.target = wrappedAction
                     }
+                    return renderedItem
+                case .toggle(let label, let value, let onChange):
+                    // Custom subclass is used to keep strong reference to action
+                    // wrapper.
+                    let renderedItem = NSCustomMenuItem(
+                        title: label,
+                        action: nil,
+                        keyEquivalent: ""
+                    )
+                    renderedItem.isOn = value
+
+                    let wrappedAction = Action {
+                        renderedItem.isOn.toggle()
+                        onChange(renderedItem.isOn)
+                    }
+                    renderedItem.actionWrapper = wrappedAction
+                    renderedItem.action = #selector(wrappedAction.run)
+                    renderedItem.target = wrappedAction
+
                     return renderedItem
                 case .submenu(let submenu):
                     return renderSubmenu(submenu)
@@ -1928,6 +1947,11 @@ final class NSCustomMenuItem: NSMenuItem {
     /// This property's only purpose is to keep a strong reference to the wrapped
     /// action so that it sticks around for long enough to be useful.
     var actionWrapper: Action?
+
+    var isOn: Bool {
+        get { state == .on }
+        set { state = newValue ? .on : .off }
+    }
 }
 
 // TODO: Update all controls to use this style of action passing, seems way nicer

Sources/SwiftCrossUI/Backend/ResolvedMenu.swift

@@ -17,6 +17,15 @@ public struct ResolvedMenu {
     public enum Item {
         /// A button. A `nil` action means that the button is disabled.
         case button(_ label: String, _ action: (@MainActor () -> Void)?)
+        /// A toggle that manages boolean state.
+        ///
+        /// Usually appears as a checkbox.
+        ///
+        /// - Parameters:
+        ///   - label: The toggle's label.
+        ///   - value: The toggle's current enabled state.
+        ///   - onChange: Called whenever the user changes the toggle's state.
+        case toggle(_ label: String, _ value: Bool, onChange: @MainActor (Bool) -> Void)
         /// A named submenu.
         case submenu(Submenu)
     }

Sources/SwiftCrossUI/Builders/MenuItemsBuilder.swift

@@ -13,6 +13,10 @@ public struct MenuItemsBuilder {
         [.text(first)]
     }
 
+    public static func buildPartialBlock(first: Toggle) -> [MenuItem] {
+        [.toggle(first)]
+    }
+
     public static func buildPartialBlock(first: Menu) -> [MenuItem] {
         [.submenu(first)]
     }
@@ -41,6 +45,13 @@ public struct MenuItemsBuilder {
         accumulated + buildPartialBlock(first: next)
     }
 
+    public static func buildPartialBlock(
+        accumulated: [MenuItem],
+        next: Toggle
+    ) -> [MenuItem] {
+        accumulated + buildPartialBlock(first: next)
+    }
+
     public static func buildPartialBlock(
         accumulated: [MenuItem],
         next: Menu

Sources/SwiftCrossUI/Scenes/CommandMenu.swift

@@ -16,6 +16,7 @@ public struct CommandMenu: Sendable {
     }
 
     /// Resolves the menu to a representation used by backends.
+    @MainActor
     func resolve() -> ResolvedMenu.Submenu {
         ResolvedMenu.Submenu(
             label: name,

Sources/SwiftCrossUI/Scenes/Commands.swift

@@ -36,6 +36,7 @@ public struct Commands: Sendable {
     }
 
     /// Resolves the menus to a representation used by backends.
+    @MainActor
     func resolve() -> [ResolvedMenu.Submenu] {
         menus.map { menu in
             menu.resolve()

Sources/SwiftCrossUI/Views/Menu.swift

@@ -14,6 +14,7 @@ public struct Menu: Sendable {
     }
 
     /// Resolves the menu to a representation used by backends.
+    @MainActor
     func resolve() -> ResolvedMenu.Submenu {
         ResolvedMenu.Submenu(
             label: label,
@@ -22,6 +23,7 @@ public struct Menu: Sendable {
     }
 
     /// Resolves the menu's items to a representation used by backends.
+    @MainActor
     static func resolveItems(_ items: [MenuItem]) -> ResolvedMenu {
         ResolvedMenu(
             items: items.map { item in
@@ -30,6 +32,12 @@ public struct Menu: Sendable {
                         .button(button.label, button.action)
                     case .text(let text):
                         .button(text.string, nil)
+                    case .toggle(let toggle):
+                        .toggle(
+                            toggle.label,
+                            toggle.active.wrappedValue,
+                            onChange: { toggle.active.wrappedValue = $0 }
+                        )
                     case .submenu(let submenu):
                         .submenu(submenu.resolve())
                 }

Sources/SwiftCrossUI/Views/MenuItem.swift

@@ -2,5 +2,6 @@
 public enum MenuItem: Sendable {
     case button(Button)
     case text(Text)
+    case toggle(Toggle)
     case submenu(Menu)
 }

Sources/UIKitBackend/UIKitBackend+Menu.swift

@@ -24,6 +24,11 @@ extension UIKitBackend {
                     } else {
                         UIAction(title: label, attributes: .disabled) { _ in }
                     }
+                case .toggle(let label, let value, let onChange):
+                    UIAction(title: label, state: value ? .on : .off) { action in
+                        action.state.isOn.toggle()
+                        onChange(action.state.isOn)
+                    }
                 case .submenu(let submenu):
                     buildMenu(content: submenu.content, label: submenu.label)
             }
@@ -70,3 +75,10 @@ extension UIKitBackend {
         #endif
     }
 }
+
+extension UIMenuElement.State {
+    var isOn: Bool {
+        get { self == .on }
+        set { self = newValue ? .on : .off }
+    }
+}

Sources/WinUIBackend/WinUIBackend.swift

@@ -285,6 +285,18 @@ public final class WinUIBackend: AppBackend {
                         action?()
                     }
                     return widget
+                case .toggle(let label, let value, let onChange):
+                    let widget = ToggleMenuFlyoutItem()
+                    widget.text = label
+                    widget.isChecked = value
+                    widget.click.addHandler { widget, _ in
+                        guard let widget = widget as? ToggleMenuFlyoutItem else {
+                            return
+                        }
+                        widget.isChecked.toggle()
+                        onChange(widget.isChecked)
+                    }
+                    return widget
                 case .submenu(let submenu):
                     let widget = MenuFlyoutSubItem()
                     widget.text = submenu.label