WinUIBackend,GtkBackend: Fix menu bar support (fixes #388) (#482)

For GtkBackend this simply fixes some ordering issues within SwiftCrossUI that prevented menu bars from getting displayed (due to Gtk limitations), and for winUIBackend this unhides the menu bar when the menu bar is non-empty (previously always hidden due to being annoying in apps without menu bars).

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)
         )