WinUIBackend: Show menu bar when non-empty, hide when empty

Author: stackotter

Sources/SwiftCrossUI/Scenes/AlertScene.swift

@@ -47,15 +47,21 @@ public final class AlertSceneNode: SceneGraphNode {
         self.scene = scene
     }
 
-    public func update<Backend: AppBackend>(
-        _ newScene: AlertScene?,
-        backend: Backend,
+    public func updateNode(
+        _ newScene: NodeScene?,
         environment: EnvironmentValues
-    ) -> SceneUpdateResult {
+    ) -> SceneNodeUpdateResult {
         if let newScene {
             self.scene = newScene
         }
 
+        return .leafScene()
+    }
+
+    public func update<Backend: AppBackend>(
+        backend: Backend,
+        environment: EnvironmentValues
+    ) {
         if scene.isPresented, alert == nil {
             let alert = backend.createAlert()
             backend.updateAlert(
@@ -75,7 +81,5 @@ public final class AlertSceneNode: SceneGraphNode {
             backend.dismissAlert(alert as! Backend.Alert, window: nil)
             self.alert = nil
         }
-
-        return .leafScene()
     }
 }

Sources/SwiftCrossUI/Scenes/Graph/SceneGraphNode.swift

@@ -26,20 +26,29 @@ public protocol SceneGraphNode: AnyObject {
         environment: EnvironmentValues
     )
 
+    /// Updates the scene's node without committing anything to screen or
+    /// propagating the update to child views.
+    ///
+    /// - Parameters:
+    ///   - newScene: The recomputed scene if the update is due to it being
+    ///     recomputed.
+    ///   - environment: The current root-level environment.
+    /// - Returns: The result of updating the scene node.
+    func updateNode(
+        _ newScene: NodeScene?,
+        environment: EnvironmentValues
+    ) -> SceneNodeUpdateResult
+
     /// Updates the scene.
     ///
     /// Unlike views (which have state), scenes are only ever updated when
     /// they're recomputed or immediately after they're created.
     ///
     /// - Parameters:
-    ///   - newScene: The recomputed scene if the update is due to it being
-    ///     recomputed.
     ///   - backend: The app's backend.
-    ///   - environment: The current root-level environment.
-    /// - Returns: The result of updating the scene.
+    ///   - environment: The current environment.
     func update<Backend: AppBackend>(
-        _ newScene: NodeScene?,
         backend: Backend,
         environment: EnvironmentValues
-    ) -> SceneUpdateResult
+    )
 }

…sUI/Scenes/Graph/SceneUpdateResult.swift …Scenes/Graph/SceneNodeUpdateResult.swiftSources/SwiftCrossUI/Scenes/Graph/SceneUpdateResult.swift renamed to Sources/SwiftCrossUI/Scenes/Graph/SceneNodeUpdateResult.swift Sources/SwiftCrossUI/Scenes/Graph/SceneUpdateResult.swift renamed to Sources/SwiftCrossUI/Scenes/Graph/SceneNodeUpdateResult.swift

@@ -1,5 +1,5 @@
-/// The result of updating a scene.
-public struct SceneUpdateResult: Sendable {
+/// The result of updating a scene graph node.
+public struct SceneNodeUpdateResult: Sendable {
     /// The preference values produced by the scene and its children.
     public var preferences: ScenePreferenceValues
 
@@ -9,13 +9,13 @@ public struct SceneUpdateResult: Sendable {
 
     /// Creates an update result by combining the preference values of a scene's
     /// children.
-    public init(childResults: [SceneUpdateResult]) {
+    public init(childResults: [SceneNodeUpdateResult]) {
         preferences = ScenePreferenceValues(merging: childResults.map(\.preferences))
     }
 
     /// Creates the layout result of a leaf scene (one with no children and no
     /// special preference behaviour). Uses ``ScenePreferenceValues/default``.
     public static func leafScene() -> Self {
-        SceneUpdateResult(preferences: .default)
+        SceneNodeUpdateResult(preferences: .default)
     }
 }

Sources/SwiftCrossUI/Scenes/Modifiers/CommandsModifier.swift

@@ -41,21 +41,26 @@ final class CommandsModifierNode<Content: Scene>: SceneGraphNode {
         )
     }
 
-    func update<Backend: AppBackend>(
+    func updateNode(
         _ newScene: NodeScene?,
-        backend: Backend,
         environment: EnvironmentValues
-    ) -> SceneUpdateResult {
+    ) -> SceneNodeUpdateResult {
         if let newScene {
             self.commands = newScene.commands
         }
 
-        var result = contentNode.update(
-            newScene?.content,
+        var result = contentNode.updateNode(newScene?.content, environment: environment)
+        result.preferences.commands = result.preferences.commands.overlayed(with: commands)
+        return result
+    }
+
+    func update<Backend: AppBackend>(
+        backend: Backend,
+        environment: EnvironmentValues
+    ) {
+        contentNode.update(
             backend: backend,
             environment: environment
         )
-        result.preferences.commands = result.preferences.commands.overlayed(with: commands)
-        return result
     }
 }

Sources/SwiftCrossUI/Scenes/Modifiers/SceneEnvironmentModifier.swift

@@ -64,17 +64,25 @@ final class SceneEnvironmentModifierNode<Content: Scene>: SceneGraphNode {
         )
     }
 
-    func update<Backend: AppBackend>(
+    func updateNode(
         _ newScene: NodeScene?,
-        backend: Backend,
         environment: EnvironmentValues
-    ) -> SceneUpdateResult {
+    ) -> SceneNodeUpdateResult {
         if let newScene {
             self.modification = newScene.modification
         }
 
-        return contentNode.update(
+        return contentNode.updateNode(
             newScene?.content,
+            environment: modification(environment)
+        )
+    }
+
+    func update<Backend: AppBackend>(
+        backend: Backend,
+        environment: EnvironmentValues
+    ) {
+        contentNode.update(
             backend: backend,
             environment: modification(environment)
         )