Add ViewControllerRepresentable support

Example/HostingExample/ViewController.swift

@@ -66,6 +66,6 @@ class ViewController: NSViewController {
 
 struct ContentView: View {
     var body: some View {
-        ColorRepresentableExample()
+        ColorViewControllerRepresentableExample()
     }
 }

Example/OpenSwiftUIUITests/Integration/Representable/PlatformViewControllerRepresentableUITests.swift

@@ -0,0 +1,48 @@
+//
+//  PlatformViewControllerRepresentableUITests.swift
+//  OpenSwiftUIUITests
+
+import Testing
+import SnapshotTesting
+
+#if os(iOS)
+import UIKit
+typealias PlatformViewControllerRepresentable = UIViewControllerRepresentable
+#elseif os(macOS)
+import AppKit
+typealias PlatformViewControllerRepresentable = NSViewControllerRepresentable
+#endif
+
+@MainActor
+@Suite(.snapshots(record: .never, diffTool: diffTool))
+struct PlatformViewControllerRepresentableUITests {
+    @Test
+    func plainColorView() {
+        struct PlainColorView: PlatformViewControllerRepresentable {
+            #if os(iOS)
+            func makeUIViewController(context: Context) -> some UIViewController {
+                let vc = UIViewController()
+                vc.view.backgroundColor = .red
+                return vc
+            }
+
+            func updateUIViewController(_ uiViewController: UIViewControllerType, context: Context) {}
+            #elseif os(macOS)
+            func makeNSViewController(context: Context) -> some NSViewController {
+                let vc = NSViewController()
+                vc.view.wantsLayer = true
+                vc.view.layer?.backgroundColor = NSColor.red.cgColor
+                return vc
+            }
+
+            func updateNSViewController(_ nsViewController: NSViewControllerType, context: Context) {}
+            #endif
+        }
+        struct ContentView: View {
+            var body: some View {
+                PlainColorView()
+            }
+        }
+        openSwiftUIAssertSnapshot(of: ContentView())
+    }
+}

Example/OpenSwiftUIUITests/Integration/Representable/PlatformViewRepresentableUITests.swift

@@ -35,7 +35,7 @@ struct PlatformViewRepresentableUITests {
                 return v
             }
 
-            func updateNSView(_ uiView: NSViewType, context: Context) {}
+            func updateNSView(_ nsView: NSViewType, context: Context) {}
             #endif
         }
         struct ContentView: View {

Example/SharedExample/Integration/Representable/ColorRepresentableExample.swift

@@ -1,5 +1,5 @@
 //
-//  ColorRepresentable.swift
+//  ColorRepresentableExample.swift
 //  SharedExample
 
 #if OPENSWIFTUI
@@ -11,12 +11,14 @@ import SwiftUI
 #if os(iOS)
 import UIKit
 typealias PlatformViewRepresentable = UIViewRepresentable
+typealias PlatformViewControllerRepresentable = UIViewControllerRepresentable
 #elseif os(macOS)
 import AppKit
 typealias PlatformViewRepresentable = NSViewRepresentable
+typealias PlatformViewControllerRepresentable = NSViewControllerRepresentable
 #endif
 
-struct ColorRepresentableExample: PlatformViewRepresentable {
+struct ColorViewRepresentableExample: PlatformViewRepresentable {
     #if os(iOS)
     func makeUIView(context: Context) -> some UIView {
         let v = UIView()
@@ -33,6 +35,26 @@ struct ColorRepresentableExample: PlatformViewRepresentable {
         return v
     }
 
-    func updateNSView(_ uiView: NSViewType, context: Context) {}
+    func updateNSView(_ nsView: NSViewType, context: Context) {}
+    #endif
+}
+
+struct ColorViewControllerRepresentableExample: PlatformViewControllerRepresentable {
+    #if os(iOS)
+    func makeUIViewController(context: Context) -> some UIViewController {
+        let vc = UIViewController()
+        vc.view.backgroundColor = .red
+        return vc
+    }
+    func updateUIViewController(_ uiViewController: UIViewControllerType, context: Context) {}
+    #elseif os(macOS)
+    func makeNSViewController(context: Context) -> some NSViewController {
+        let vc = NSViewController()
+        vc.view.wantsLayer = true
+        vc.view.layer?.backgroundColor = NSColor.red.cgColor
+        return vc
+    }
+
+    func updateNSViewController(_ nsViewController: NSViewControllerType, context: Context) {}
     #endif
 }

Sources/OpenSwiftUI/Integration/Hosting/AppKit/View/NSHostingView.swift

@@ -267,6 +267,13 @@ open class NSHostingView<Content>: NSView, XcodeViewDebugDataProvider where Cont
         needsUpdateConstraints = true
         needsLayout = true
     }
+
+    @objc(swiftui_addRenderedSubview:positioned:relativeTo:) // FIXME: ViewUpdater -> AppKitAddSubview
+    private func openswiftui_addRenderedSubview(_ view: NSView, positioned place: NSWindow.OrderingMode, relativeTo otherView: NSView?) {
+        isInsertingRenderedSubview = true
+        addSubview(view, positioned: place, relativeTo: otherView)
+        isInsertingRenderedSubview = false
+    }
 }
 
 @available(iOS, unavailable)

Sources/OpenSwiftUI/Integration/Hosting/Platform/IsInHostingConfiguration.swift

@@ -0,0 +1,26 @@
+//
+//  IsInHostingConfiguration.swift
+//  OpenSwiftUI
+//
+//  Audited for 6.5.4
+//  Status: Complete
+
+import OpenSwiftUICore
+
+struct IsInHostingConfiguration: ViewInputBoolFlag {}
+
+extension _GraphInputs {
+    @inline(__always)
+    var isInHostingConfiguration: Bool {
+        get { IsInHostingConfiguration.evaluate(inputs: self) }
+        set { self[IsInHostingConfiguration.self] = newValue }
+    }
+}
+
+extension _ViewInputs {
+    @inline(__always)
+    var isInHostingConfiguration: Bool {
+        get { base.isInHostingConfiguration }
+        set { base.isInHostingConfiguration = newValue }
+    }
+}

Sources/OpenSwiftUI/Integration/Hosting/UIKit/View/UIHostingView.swift

@@ -347,6 +347,13 @@ open class _UIHostingView<Content>: UIView, XcodeViewDebugDataProvider where Con
             inputs.base.options.insert(.supportsVariableFrameDuration)
         }
     }
+
+    @objc(swiftui_insertRenderedSubview:atIndex:) // FIXME: ViewUpdater -> CoreViewAddSubview
+    private func openswiftui_insertRenderedSubview(_ view: UIView, at index: Int) {
+        isInsertingRenderedSubview = true
+        insertSubview(view, at: index)
+        isInsertingRenderedSubview = false
+    }
 }
 
 extension _UIHostingView {
@@ -470,8 +477,12 @@ extension _UIHostingView {
 extension _UIHostingView: ViewRendererHost {
     package func `as`<T>(_ type: T.Type) -> T? {
         guard let value = base.as(type) else {
-            // TODO
-            return nil
+            // FocusHost
+            if UIViewControllerProvider.self == type {
+                return unsafeBitCast(self as any UIViewControllerProvider, to: T.self)
+            } else { // TODO
+                return nil
+            }
         }
         return value
     }
@@ -690,4 +701,12 @@ extension _UIHostingView: UIHostingViewBaseDelegate {
     }
 }
 
+// MARK: - _UIHostingView + UIViewControllerProvider [6.5.4]
+
+extension _UIHostingView: UIViewControllerProvider {
+    var uiViewController: UIViewController? {
+        viewController
+    }
+}
+
 #endif

Sources/OpenSwiftUI/Integration/Hosting/UIKit/View/UIViewControllerProvider.swift

@@ -0,0 +1,28 @@
+//
+//  UIViewControllerProvider.swift
+//  OpenSwiftUI
+//
+//  Audited for 6.5.4
+//  Status: Complete
+
+#if os(iOS)
+
+import UIKit
+
+protocol UIViewControllerProvider: AnyObject {
+    var uiViewController: UIViewController? { get }
+}
+
+extension UIViewControllerProvider {
+    var containingViewController: UIViewController? {
+        if let uiViewController {
+            return uiViewController
+        } else if let view = self as? UIView {
+            return view._viewControllerForAncestor
+        } else {
+            return nil
+        }
+    }
+}
+
+#endif