Add PlatformViewRepresentable support

Example/HostingExample/ViewController.swift

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

Example/OpenSwiftUIUITests/Integration/Representable/PlatformViewRepresentableUITests.swift

@@ -0,0 +1,48 @@
+//
+//  PlatformViewRepresentableUITests.swift
+//  OpenSwiftUIUITests
+
+import Testing
+import SnapshotTesting
+
+#if os(iOS)
+import UIKit
+typealias PlatformViewRepresentable = UIViewRepresentable
+#elseif os(macOS)
+import AppKit
+typealias PlatformViewRepresentable = NSViewRepresentable
+#endif
+
+@MainActor
+@Suite(.snapshots(record: .never, diffTool: diffTool))
+struct PlatformViewRepresentableUITests {
+    @Test
+    func plainColorView() {
+        struct PlainColorView: PlatformViewRepresentable {
+            #if os(iOS)
+            func makeUIView(context: Context) -> some UIView {
+                let v = UIView()
+                v.backgroundColor = .red
+                return v
+            }
+
+            func updateUIView(_ uiView: UIViewType, context: Context) {}
+            #elseif os(macOS)
+            func makeNSView(context: Context) -> some NSView {
+                let v = NSView()
+                v.wantsLayer = true
+                v.layer?.backgroundColor = NSColor.red.cgColor
+                return v
+            }
+
+            func updateNSView(_ uiView: NSViewType, context: Context) {}
+            #endif
+        }
+        struct ContentView: View {
+            var body: some View {
+                PlainColorView()
+            }
+        }
+        openSwiftUIAssertSnapshot(of: ContentView())
+    }
+}

Example/SharedExample/Integration/Representable/ColorRepresentableExample.swift

@@ -0,0 +1,38 @@
+//
+//  ColorRepresentable.swift
+//  SharedExample
+
+#if OPENSWIFTUI
+import OpenSwiftUI
+#else
+import SwiftUI
+#endif
+
+#if os(iOS)
+import UIKit
+typealias PlatformViewRepresentable = UIViewRepresentable
+#elseif os(macOS)
+import AppKit
+typealias PlatformViewRepresentable = NSViewRepresentable
+#endif
+
+struct ColorRepresentableExample: PlatformViewRepresentable {
+    #if os(iOS)
+    func makeUIView(context: Context) -> some UIView {
+        let v = UIView()
+        v.backgroundColor = .red
+        return v
+    }
+
+    func updateUIView(_ uiView: UIViewType, context: Context) {}
+    #elseif os(macOS)
+    func makeNSView(context: Context) -> some NSView {
+        let v = NSView()
+        v.wantsLayer = true
+        v.layer?.backgroundColor = NSColor.red.cgColor
+        return v
+    }
+
+    func updateNSView(_ uiView: NSViewType, context: Context) {}
+    #endif
+}

Sources/OpenSwiftUI/Event/Focus/FocusedValueKey.swift

@@ -6,6 +6,7 @@
 //  Status: WIP
 
 import OpenSwiftUICore
+import OpenGraphShims
 
 @available(OpenSwiftUI_v2_0, *)
 @propertyWrapper
@@ -99,3 +100,10 @@ extension FocusedValues: Equatable {
         lhs.seed.matches(rhs.seed)
     }
 }
+
+// FIXME
+struct FocusedValuesInputKey: ViewInput {
+    static var defaultValue: OptionalAttribute<FocusedValues> {
+        .init()
+    }
+}

Sources/OpenSwiftUI/Integration/Render/AppKit/NSViewPlatformViewDefinition.swift

@@ -59,5 +59,17 @@ final class NSViewPlatformViewDefinition: PlatformViewDefinition, @unchecked Sen
     override static func makeLayerView(type: CALayer.Type, kind: PlatformViewDefinition.ViewKind) -> AnyObject {
         _openSwiftUIUnimplementedFailure()
     }
+
+    override class func makePlatformView(view: AnyObject, kind: PlatformViewDefinition.ViewKind) {
+        Self.initView(view as! NSView, kind: kind)
+    }
+
+    override class func setAllowsWindowActivationEvents(_ value: Bool?, for view: AnyObject) {
+        _openSwiftUIUnimplementedWarning()
+    }
+
+    override class func setHitTestsAsOpaque(_ value: Bool, for view: AnyObject) {
+        _openSwiftUIUnimplementedWarning()
+    }
 }
 #endif

Sources/OpenSwiftUI/Integration/Render/UIKit/UIViewPlatformViewDefinition.swift

@@ -54,5 +54,9 @@ final class UIViewPlatformViewDefinition: PlatformViewDefinition, @unchecked Sen
             break
         }
     }
+
+    override class func makePlatformView(view: AnyObject, kind: PlatformViewDefinition.ViewKind) {
+        Self.initView(view as! UIView, kind: kind)
+    }
 }
 #endif

Sources/OpenSwiftUI/Integration/Representable/AppKit/NSViewControllerRepresentable.swift

@@ -0,0 +1,6 @@
+//
+//  NSViewControllerRepresentable.swift
+//  OpenSwiftUI
+
+// TODO
+package struct NSViewControllerRepresentable {}