Scene phases

.swift-version

@@ -0,0 +1 @@
+6.2.4

Examples/Sources/WindowingExample/WindowingApp.swift

@@ -194,11 +194,14 @@ struct TertiaryWindowView: View {
 
 struct SingletonWindowView: View {
     @Environment(\.dismissWindow) private var dismissWindow
+    @Environment(\.scenePhase) private var scenePhase
 
     var body: some View {
         VStack {
             Text("This a singleton window!")
 
+            Text("Window scene phase: \(scenePhase)")
+
             Button("Close window") {
                 dismissWindow()
             }
@@ -218,6 +221,8 @@ struct WindowingApp: App {
     @State var closable = true
     @State var minimizable = true
 
+    @Environment(\.scenePhase) var scenePhase
+
     var bannerImage: URL {
         // TODO(stackotter): Update SwiftBundlerRuntime to support fetching
         //   resources in a cross platform manner.
@@ -241,6 +246,8 @@ struct WindowingApp: App {
                         TextField("My window", text: $title)
                     }
 
+                    Text("App scene phase: \(scenePhase)")
+
                     Toggle("Enable resizing", isOn: $resizable)
                         .windowResizeBehavior(resizable ? .enabled : .disabled)
                     Toggle("Enable closing", isOn: $closable)

Sources/AppKitBackend/AppKitBackend.swift

@@ -165,6 +165,14 @@
         window.makeKeyAndOrderFront(nil)
     }
 
+    public func isWindowActive(_ window: Window) -> Bool {
+        return window.isKeyWindow
+    }
+
+    public func isApplicationActive() -> Bool {
+        return NSApplication.shared.isActive
+    }
+
     public func setApplicationMenu(_ submenus: [ResolvedMenu.Submenu]) {
         MenuBar.setUpMenuBar(extraMenus: submenus.map(Self.renderSubmenu(_:)))
     }
@@ -283,6 +291,22 @@
         ) { _ in
             action()
         }
+
+        // For updating views that rely on `scenePhase`
+        NotificationCenter.default.addObserver(
+            forName: NSApplication.didBecomeActiveNotification,
+            object: nil,
+            queue: .main
+        ) { _ in
+            action()
+        }
+        NotificationCenter.default.addObserver(
+            forName: NSApplication.didResignActiveNotification,
+            object: nil,
+            queue: .main
+        ) { _ in
+            action()
+        }
     }
 
     public func computeWindowEnvironment(
@@ -311,6 +335,22 @@
                 action()
             }
         }
+
+        // For updating views that rely on `scenePhase`
+        NotificationCenter.default.addObserver(
+            forName: NSWindow.didBecomeKeyNotification,
+            object: nil,
+            queue: .main
+        ) { _ in
+            action()
+        }
+        NotificationCenter.default.addObserver(
+            forName: NSWindow.didResignKeyNotification,
+            object: nil,
+            queue: .main
+        ) { _ in
+            action()
+        }
     }
 
     public func setIncomingURLHandler(to action: @escaping (URL) -> Void) {
@@ -445,7 +485,7 @@
     func setSize(of widget: Widget, to proposedSize: ProposedViewSize) {
         var foundConstraint = false
         for constraint in widget.constraints {
             if constraint.firstAnchor === widget.widthAnchor {
                 if let proposedWidth = proposedSize.width {
                     constraint.constant = CGFloat(proposedWidth)
                     constraint.isActive = true
@@ -463,7 +503,7 @@
 
         foundConstraint = false
         for constraint in widget.constraints {
             if constraint.firstAnchor === widget.heightAnchor {
                 if let proposedHeight = proposedSize.height {
                     constraint.constant = CGFloat(proposedHeight)
                     constraint.isActive = true
@@ -654,7 +694,7 @@
         environment: EnvironmentValues,
         onChange: @escaping (Double) -> Void
     ) {
         // TODO: Implement decimalPlaces
         let slider = slider as! NSSlider
         slider.minValue = minimum
         slider.maxValue = maximum
@@ -774,7 +814,7 @@
                         .name
                     case .emailAddress:
                         .emailAddress
                     case .text, .digits(_), .decimal(_):
                         nil
                 }
         }
@@ -828,7 +868,7 @@
                         .name
                     case .emailAddress:
                         .emailAddress
                     case .text, .digits(_), .decimal(_):
                         nil
                 }
         }
@@ -918,7 +958,7 @@
     public func baseItemPadding(
         ofSelectableListView listView: Widget
     ) -> SwiftCrossUI.EdgeInsets {
         // TODO: Figure out if there's a way to compute this more directly. At
         //   the moment these are just figures from empirical observations.
         SwiftCrossUI.EdgeInsets(top: 0, bottom: 0, leading: 8, trailing: 8)
     }
@@ -1342,7 +1382,7 @@
         panel.showsHiddenFiles = fileDialogOptions.showHiddenFiles
         panel.allowsOtherFileTypes = fileDialogOptions.allowOtherContentTypes
 
         // TODO: allowedContentTypes
 
         panel.allowsMultipleSelection = openDialogOptions.allowMultipleSelections
         panel.canChooseFiles = openDialogOptions.allowSelectingFiles
@@ -1381,7 +1421,7 @@
         panel.showsHiddenFiles = fileDialogOptions.showHiddenFiles
         panel.allowsOtherFileTypes = fileDialogOptions.allowOtherContentTypes
 
         // TODO: allowedContentTypes
 
         panel.nameFieldLabel = saveDialogOptions.nameFieldLabel ?? panel.nameFieldLabel
         panel.nameFieldStringValue = saveDialogOptions.defaultFileName ?? ""

Sources/DummyBackend/DummyBackend.swift

@@ -15,6 +15,7 @@ public final class DummyBackend: AppBackend {
         public var content: Widget?
         public var resizeHandler: ((SIMD2<Int>) -> Void)?
         public var closeHandler: (() -> Void)?
+        public var isActive = false
 
         public init(defaultSize: SIMD2<Int>?) {
             size = defaultSize ?? Self.defaultSize
@@ -256,6 +257,7 @@ public final class DummyBackend: AppBackend {
     public var supportedPickerStyles: [BackendPickerStyle] = []
 
     public var incomingURLHandler: ((URL) -> Void)?
+    public var isAppActive = true
 
     public init() {}
 
@@ -312,9 +314,21 @@ public final class DummyBackend: AppBackend {
         window.resizeHandler = action
     }
 
-    public func show(window: Window) {}
+    public func show(window: Window) {
+        window.isActive = true
+    }
+
+    public func activate(window: Window) {
+        window.isActive = true
+    }
 
-    public func activate(window: Window) {}
+    public func isWindowActive(_ window: Window) -> Bool {
+        window.isActive
+    }
+
+    public func isApplicationActive() -> Bool {
+        isAppActive
+    }
 
     public func close(window: Window) {
         window.closeHandler?()

Sources/Gtk/Widgets/ApplicationWindow.swift

@@ -12,5 +12,27 @@ public class ApplicationWindow: Window {
         registerSignals()
     }
 
+    public override func registerSignals() {
+        super.registerSignals()
+
+        let handler2:
+            @convention(c) (
+                UnsafeMutableRawPointer,
+                gboolean,
+                UnsafeMutableRawPointer
+            ) -> Void = { _, value1, data in
+                SignalBox1<gboolean>.run(data, value1)
+            }
+        addSignal(
+            name: "notify::is-active",
+            handler: gCallback(handler2)
+        ) { [weak self] (isActive: gboolean) in
+            guard let self else { return }
+            self.notifyIsActive?(isActive != 0)
+        }
+    }
+
+    public var notifyIsActive: ((Bool) -> Void)?
+
     @GObjectProperty(named: "show-menubar") public var showMenuBar: Bool
 }

Sources/Gtk/Widgets/Window.swift

@@ -19,6 +19,10 @@ open class Window: Widget {
     @GObjectProperty(named: "decorated") public var isDecorated: Bool
     @GObjectProperty(named: "destroy-with-parent") public var destroyWithParent: Bool
 
+    public var isActive: Bool {
+        gtk_window_is_active(castedPointer()).toBool()
+    }
+
     public func setTransient(for other: Window) {
         gtk_window_set_transient_for(castedPointer(), other.castedPointer())
     }

Sources/Gtk3/Widgets/ApplicationWindow.swift

@@ -23,17 +23,33 @@ public class ApplicationWindow: Window {
             ) -> Void = { _, value1, data in
                 SignalBox1<gint>.run(data, value1)
             }
-
         addSignal(
             name: "notify::scale-factor",
             handler: gCallback(handler2)
         ) { [weak self] (scaleFactor: gint) in
             guard let self else { return }
             self.notifyScaleFactor?(Int(scaleFactor))
         }
+
+        let handler3:
+            @convention(c) (
+                UnsafeMutableRawPointer,
+                gboolean,
+                UnsafeMutableRawPointer
+            ) -> Void = { _, value1, data in
+                SignalBox1<gboolean>.run(data, value1)
+            }
+        addSignal(
+            name: "notify::is-active",
+            handler: gCallback(handler3)
+        ) { [weak self] (isActive: gboolean) in
+            guard let self else { return }
+            self.notifyIsActive?(isActive != 0)
+        }
     }
 
     public var notifyScaleFactor: ((Int) -> Void)?
+    public var notifyIsActive: ((Bool) -> Void)?
 
     @GObjectProperty(named: "show-menubar") public var showMenuBar: Bool
 }

Sources/Gtk3/Widgets/Window.swift

@@ -16,6 +16,10 @@ open class Window: Bin {
     @GObjectProperty(named: "modal") public var isModal: Bool
     @GObjectProperty(named: "decorated") public var isDecorated: Bool
 
+    public var isActive: Bool {
+        gtk_window_is_active(castedPointer()).toBool()
+    }
+
     public func setTransient(for other: Window) {
         gtk_window_set_transient_for(castedPointer(), other.castedPointer())
     }

Sources/Gtk3Backend/Gtk3Backend.swift

@@ -365,6 +365,14 @@ public final class Gtk3Backend: AppBackend {
         window.present()
     }
 
+    public func isWindowActive(_ window: Window) -> Bool {
+        window.isActive
+    }
+
+    public func isApplicationActive() -> Bool {
+        windows.contains(where: \.isActive)
+    }
+
     public func close(window: Window) {
         window.close()
 
@@ -503,6 +511,7 @@ public final class Gtk3Backend: AppBackend {
 
     public func setRootEnvironmentChangeHandler(to action: @escaping () -> Void) {
         // TODO: React to theme changes
+        // TODO: Notify when app focus changes
     }
 
     public func computeWindowEnvironment(
@@ -516,10 +525,13 @@ public final class Gtk3Backend: AppBackend {
     public func setWindowEnvironmentChangeHandler(
         of window: Window,
         to action: @escaping () -> Void
-    ) {
+    ) {        
         window.notifyScaleFactor = { _ in
             action()
         }
+        window.notifyIsActive = { _ in
+            action()
+        }
     }
 
     public func setIncomingURLHandler(to action: @escaping (URL) -> Void) {

Sources/GtkBackend/GtkBackend.swift

@@ -259,6 +259,14 @@ public final class GtkBackend: AppBackend {
         window.present()
     }
 
+    public func isWindowActive(_ window: Window) -> Bool {
+        window.isActive
+    }
+
+    public func isApplicationActive() -> Bool {
+        windows.contains(where: \.isActive)
+    }
+
     public func close(window: Window) {
         window.close()
     }
@@ -471,6 +479,7 @@ public final class GtkBackend: AppBackend {
 
     public func setRootEnvironmentChangeHandler(to action: @escaping () -> Void) {
         // TODO: React to theme changes
+        // TODO: Notify when app focus changes
     }
 
     public func computeWindowEnvironment(
@@ -486,6 +495,10 @@ public final class GtkBackend: AppBackend {
         to action: @escaping () -> Void
     ) {
         // TODO: Notify when window scale factor changes
+
+        window.notifyIsActive = { _ in
+            action()
+        }
     }
 
     public func setIncomingURLHandler(to action: @escaping (URL) -> Void) {

Sources/SwiftCrossUI/Backend/AppBackend.swift

@@ -283,6 +283,16 @@ public protocol AppBackend: Sendable {
         to action: @escaping () -> Void
     )
 
+    /// Returns whether the given window is currently active.
+    func isWindowActive(_ window: Window) -> Bool
+
+    /// Returns whether the application is currently active.
+    ///
+    /// Usually this returns `true` if and only if any of the app's windows are
+    /// active, but on platforms such as macOS it can also return `true` if the
+    /// app doesn't have any open windows but still appears in the menu bar.
+    func isApplicationActive() -> Bool
+
     /// Sets the application's global menu.
     ///
     /// Some backends may make use of the host platform's global menu bar

Sources/SwiftCrossUI/Environment/EnvironmentValues.swift

@@ -184,6 +184,22 @@ public struct EnvironmentValues {
         RevealFileAction(backend: backend)
     }
 
+    /// The active state of the current scene (or, if accessed outside of a scene,
+    /// the app as a whole).
+    @MainActor
+    public var scenePhase: ScenePhase {
+        func scenePhase<Backend: AppBackend>(backend: Backend) -> ScenePhase {
+            let isActive = if let window {
+                backend.isWindowActive(window as! Backend.Window)
+            } else {
+                backend.isApplicationActive()
+            }
+            return if isActive { .active } else { .inactive }
+        }
+
+        return scenePhase(backend: backend)
+    }
+
     /// Whether the backend can have multiple windows open at once. Mobile
     /// backends generally can't.
     @MainActor

Sources/SwiftCrossUI/Values/ScenePhase.swift

@@ -0,0 +1,9 @@
+/// The active state of a scene or app.
+public enum ScenePhase: Hashable, Sendable {
+    /// The scene is active.
+    case active
+    /// The scene is inactive.
+    case inactive
+
+    // TODO: Figure out how .background would work on desktops
+}

Sources/UIKitBackend/UIKitBackend+Window.swift

@@ -128,6 +128,14 @@ extension UIKitBackend {
         window.makeKeyAndVisible()
     }
 
+    public func isWindowActive(_ window: Window) -> Bool {
+        window.isKeyWindow
+    }
+
+    public func isApplicationActive() -> Bool {
+        UIApplication.shared.applicationState == .active
+    }
+
     public func close(window: Window) {
         logger.notice("UIKitBackend: ignoring \(#function) call")
     }

Sources/WinUIBackend/WinUIBackend.swift

@@ -288,6 +288,14 @@ public final class WinUIBackend: AppBackend {
         try! window.activate()
     }
 
+    public func isWindowActive(_ window: Window) -> Bool {
+        window.isActive
+    }
+
+    public func isApplicationActive() -> Bool {
+        windows.contains(where: \.isActive)
+    }
+
     public func close(window: Window) {
         try! window.close()
     }
@@ -2216,6 +2224,7 @@ public class CustomWindow: WinUI.Window {
     var child: WinUIBackend.Widget?
     var grid: WinUI.Grid
     var cachedAppWindow: WinAppSDK.AppWindow!
+    var isActive = false
 
     private(set) var menuBarIsVisible = false
 
@@ -2265,6 +2274,15 @@ public class CustomWindow: WinUI.Window {
         WinUI.Grid.setRow(menuBar, 0)
         self.content = grid
 
+        // NB: This event fires when the window is activated _or_ deactivated.
+        self.activated.addHandler { [weak self] _, args in
+            switch args?.windowActivationState {
+                case .activated: self?.isActive = true
+                case .deactivated: self?.isActive = false
+                default: break
+            }
+        }
+
         // Caching appWindow is apparently a good idea in terms of performance:
         // https://github.com/thebrowsercompany/swift-winrt/issues/199#issuecomment-2611006020
         cachedAppWindow = appWindow