Implement a basic scene graph (which so far only supports having a si…

…ngle view) and update examples accordingly

This change was made to be able to introduce multi-windowing and get also get rid of the windowProperties
property currently required to configure the app's window. I've basically followed SwiftUI's API, but
probably not their implementation at all. This was so much easier to figure out after having grappled
with the ViewGraph for so long yesterday.

Examples/Counter/CounterApp.swift

@@ -16,12 +16,14 @@ struct CounterApp: App {
 
     let windowProperties = WindowProperties(title: "CounterApp", resizable: true)
 
-    var body: some View {
-        HStack(spacing: 20) {
-            Button("-") { state.count -= 1 }
-            Text("Count: \(state.count)", wrap: false)
-            Button("+") { state.count += 1 }
+    var body: some Scene {
+        WindowGroup {
+            HStack(spacing: 20) {
+                Button("-") { state.count -= 1 }
+                Text("Count: \(state.count)", wrap: false)
+                Button("+") { state.count += 1 }
+            }
+            .padding(10)
         }
-        .padding(10)
     }
 }

Examples/FileViewer/FileViewerApp.swift

@@ -24,25 +24,27 @@ struct FileViewerApp: App {
         resizable: false
     )
 
-    var body: some View {
-        #if canImport(FileDialog)
-            HStack {
-                VStack {
-                    Text("Selected file: \(state.file?.path ?? "none")")
-
-                    Button("Click") {
-                        let dialog = FileDialog()
-                        dialog.open { result in
-                            guard case let .success(file) = result else {
-                                return
+    var body: some Scene {
+        WindowGroup {
+            #if canImport(FileDialog)
+                HStack {
+                    VStack {
+                        Text("Selected file: \(state.file?.path ?? "none")")
+
+                        Button("Click") {
+                            let dialog = FileDialog()
+                            dialog.open { result in
+                                guard case let .success(file) = result else {
+                                    return
+                                }
+                                state.file = file
                             }
-                            state.file = file
                         }
-                    }
-                }.padding(10)
-            }
-        #else
-            Text("FileDialog requires Gtk 4.10")
-        #endif
+                    }.padding(10)
+                }
+            #else
+                Text("FileDialog requires Gtk 4.10")
+            #endif
+        }
     }
 }

Examples/GreetingGenerator/GreetingGenerator.swift

@@ -16,36 +16,38 @@ struct GreetingGeneratorApp: App {
 
     let windowProperties = WindowProperties(title: "Greeting Generator")
 
-    var body: some View {
-        VStack {
-            TextField("Name", state.$name)
-            HStack {
-                Button("Generate") {
-                    state.greetings.append("Hello, \(state.name)!")
-                }
-                Button("Reset") {
-                    state.greetings = []
-                    state.name = ""
+    var body: some Scene {
+        WindowGroup {
+            VStack {
+                TextField("Name", state.$name)
+                HStack {
+                    Button("Generate") {
+                        state.greetings.append("Hello, \(state.name)!")
+                    }
+                    Button("Reset") {
+                        state.greetings = []
+                        state.name = ""
+                    }
                 }
-            }
 
-            if let latest = state.greetings.last {
-                Text(latest)
-                    .padding(.top, 5)
+                if let latest = state.greetings.last {
+                    Text(latest)
+                        .padding(.top, 5)
 
-                if state.greetings.count > 1 {
-                    Text("History:")
-                        .padding(.top, 20)
+                    if state.greetings.count > 1 {
+                        Text("History:")
+                            .padding(.top, 20)
 
-                    ScrollView {
-                        ForEach(state.greetings.reversed()[1...]) { greeting in
-                            Text(greeting)
+                        ScrollView {
+                            ForEach(state.greetings.reversed()[1...]) { greeting in
+                                Text(greeting)
+                            }
                         }
+                        .padding(.top, 8)
                     }
-                    .padding(.top, 8)
                 }
             }
+            .padding(10)
         }
-        .padding(10)
     }
 }

Examples/Navigation/NavigationApp.swift

@@ -38,53 +38,58 @@ struct NavigationApp: App {
         defaultSize: WindowProperties.Size(200, 250)
     )
 
-    var body: some View {
-        NavigationStack(path: state.$path) {
-            Text("Learn about subject areas")
-                .padding(.bottom, 10)
-
-            NavigationLink("Science", value: SubjectArea.science, path: state.$path)
-            NavigationLink("Humanities", value: SubjectArea.humanities, path: state.$path)
-        }
-        .navigationDestination(for: SubjectArea.self) { area in
-            switch area {
-                case .science:
-                    Text("Choose a science subject")
-                        .padding(.bottom, 10)
-
-                    NavigationLink("Physics", value: ScienceSubject.physics, path: state.$path)
-                    NavigationLink("Chemistry", value: ScienceSubject.chemistry, path: state.$path)
-                case .humanities:
-                    Text("Choose a humanities subject")
-                        .padding(.bottom, 10)
-
-                    NavigationLink("English", value: HumanitiesSubject.english, path: state.$path)
-                    NavigationLink("History", value: HumanitiesSubject.history, path: state.$path)
+    var body: some Scene {
+        WindowGroup {
+            NavigationStack(path: state.$path) {
+                Text("Learn about subject areas")
+                    .padding(.bottom, 10)
+
+                NavigationLink("Science", value: SubjectArea.science, path: state.$path)
+                NavigationLink("Humanities", value: SubjectArea.humanities, path: state.$path)
             }
-
-            backButton
-        }
-        .navigationDestination(for: ScienceSubject.self) { subject in
-            switch subject {
-                case .physics:
-                    Text("Physics is applied maths")
-                case .chemistry:
-                    Text("Chemistry is applied physics")
+            .navigationDestination(for: SubjectArea.self) { area in
+                switch area {
+                    case .science:
+                        Text("Choose a science subject")
+                            .padding(.bottom, 10)
+
+                        NavigationLink("Physics", value: ScienceSubject.physics, path: state.$path)
+                        NavigationLink(
+                            "Chemistry", value: ScienceSubject.chemistry, path: state.$path)
+                    case .humanities:
+                        Text("Choose a humanities subject")
+                            .padding(.bottom, 10)
+
+                        NavigationLink(
+                            "English", value: HumanitiesSubject.english, path: state.$path)
+                        NavigationLink(
+                            "History", value: HumanitiesSubject.history, path: state.$path)
+                }
+
+                backButton
             }
-
-            backButton
-        }
-        .navigationDestination(for: HumanitiesSubject.self) { subject in
-            switch subject {
-                case .english:
-                    Text("I don't like essays")
-                case .history:
-                    Text("Don't repeat it")
+            .navigationDestination(for: ScienceSubject.self) { subject in
+                switch subject {
+                    case .physics:
+                        Text("Physics is applied maths")
+                    case .chemistry:
+                        Text("Chemistry is applied physics")
+                }
+
+                backButton
             }
-
-            backButton
+            .navigationDestination(for: HumanitiesSubject.self) { subject in
+                switch subject {
+                    case .english:
+                        Text("I don't like essays")
+                    case .history:
+                        Text("Don't repeat it")
+                }
+
+                backButton
+            }
+            .padding(10)
         }
-        .padding(10)
     }
 
     @ViewBuilder

Examples/RandomNumberGenerator/RandomNumberGeneratorApp.swift

@@ -38,40 +38,42 @@ struct RandomNumberGeneratorApp: App {
         defaultSize: .init(500, 0)
     )
 
-    var body: some View {
-        VStack {
-            Text("Random Number: \(state.randomNumber)")
-            Button("Generate") {
-                state.randomNumber = Int.random(in: Int(state.minNum)...Int(state.maxNum))
-            }
+    var body: some Scene {
+        WindowGroup {
+            VStack {
+                Text("Random Number: \(state.randomNumber)")
+                Button("Generate") {
+                    state.randomNumber = Int.random(in: Int(state.minNum)...Int(state.maxNum))
+                }
 
-            Text("Minimum:")
-            Slider(
-                state.$minNum.onChange { newValue in
-                    if newValue > state.maxNum {
-                        state.minNum = state.maxNum
-                    }
-                },
-                minimum: 0,
-                maximum: 100
-            )
+                Text("Minimum:")
+                Slider(
+                    state.$minNum.onChange { newValue in
+                        if newValue > state.maxNum {
+                            state.minNum = state.maxNum
+                        }
+                    },
+                    minimum: 0,
+                    maximum: 100
+                )
 
-            Text("Maximum:")
-            Slider(
-                state.$maxNum.onChange { newValue in
-                    if newValue < state.minNum {
-                        state.maxNum = state.minNum
-                    }
-                },
-                minimum: 0,
-                maximum: 100
-            )
+                Text("Maximum:")
+                Slider(
+                    state.$maxNum.onChange { newValue in
+                        if newValue < state.minNum {
+                            state.maxNum = state.minNum
+                        }
+                    },
+                    minimum: 0,
+                    maximum: 100
+                )
 
-            Text("Choose a color:")
-                .padding(.top, 20)
-            Picker(of: ColorOption.allCases, selection: state.$colorOption)
+                Text("Choose a color:")
+                    .padding(.top, 20)
+                Picker(of: ColorOption.allCases, selection: state.$colorOption)
+            }
+            .padding(10)
+            .foregroundColor(state.colorOption?.color ?? .red)
         }
-        .padding(10)
-        .foregroundColor(state.colorOption?.color ?? .red)
     }
 }

Examples/Split/SplitApp.swift

@@ -41,12 +41,14 @@ struct SplitApp: App {
         defaultSize: WindowProperties.Size(600, 250)
     )
 
-    var body: some View {
-        switch state.columns {
-            case .two:
-                doubleColumn
-            case .three:
-                tripleColumn
+    var body: some Scene {
+        WindowGroup {
+            switch state.columns {
+                case .two:
+                    doubleColumn
+                case .three:
+                    tripleColumn
+            }
         }
     }
 

Examples/Spreadsheet/SpreadsheetApp.swift

@@ -33,14 +33,16 @@ struct SpreadsheetApp: App {
 
     let windowProperties = WindowProperties(title: "SpreadsheetApp", resizable: true)
 
-    var body: some View {
-        Table(state.data) {
-            TableColumn("Name", value: \Person.name)
-            TableColumn("Age", value: \Person.age)
-            TableColumn("Phone", value: \Person.phone)
-            TableColumn("Email", value: \Person.email)
-            TableColumn("Occupation", value: \Person.occupation)
+    var body: some Scene {
+        WindowGroup {
+            Table(state.data) {
+                TableColumn("Name", value: \Person.name)
+                TableColumn("Age", value: \Person.age)
+                TableColumn("Phone", value: \Person.phone)
+                TableColumn("Email", value: \Person.email)
+                TableColumn("Occupation", value: \Person.occupation)
+            }
+            .padding(10)
         }
-        .padding(10)
     }
 }