Update UIHosting implementation to fix HostingExample example

Sources/OpenSwiftUI/CoreGlue/OpenSwiftUIGlue.swift

@@ -0,0 +1,24 @@
+//
+//  OpenSwiftUIGlue.swift
+//  OpenSwiftUI
+//
+//  Audited for iOS 18.0
+//  Status: Empty
+
+@_spi(ForOpenSwiftUIOnly)
+import OpenSwiftUICore
+
+#if canImport(Darwin)
+
+@_cdecl("OpenSwiftUIGlueClass")
+func OpenSwiftUIGlueClass() -> CoreGlue.Type {
+    OpenSwiftUIGlue.self
+}
+
+final class OpenSwiftUIGlue: CoreGlue {
+    override func makeDefaultLayoutComputer() -> MakeDefaultLayoutComputerResult {
+        MakeDefaultLayoutComputerResult(value: ViewGraph.current.$defaultLayoutComputer)
+    }
+}
+
+#endif

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

@@ -0,0 +1,44 @@
+//
+//  HostingViewRegistry.swift
+//  OpenSwiftUI
+//
+//  Audited for iOS 18.0
+//  Status: Complete
+//  ID: 08E507B775941708E73E5FD8531D9361 (SwiftUI)
+
+@_spi(Private)
+public import OpenSwiftUICore
+
+@_spi(Private)
+public protocol HostingViewProtocol: AnyObject {
+    func preferenceValue<K>(_ key: K.Type) -> K.Value where K: HostPreferenceKey
+    func convertAnchor<Value>(_ anchor: Anchor<Value>) -> Value
+}
+
+@_spi(Private)
+public class HostingViewRegistry {
+    public static let shared: HostingViewRegistry = HostingViewRegistry()
+
+    public func forEach(_ body: (any HostingViewProtocol) throws -> Void) rethrows {
+        try elements.values.forEach { box in
+            guard let element = box.base as? HostingViewProtocol else {
+                return
+            }
+            try body(element)
+        }
+    }
+
+    private var elements: [ObjectIdentifier: WeakBox<AnyObject>] = [:]
+
+    func add<V>(_ element: V) where V: HostingViewProtocol {
+        elements[ObjectIdentifier(element)] = WeakBox(element)
+    }
+
+    func remove<V>(_ element: V) where V: HostingViewProtocol {
+        elements.removeValue(forKey: ObjectIdentifier(element))
+    }
+}
+
+@_spi(Private)
+@available(*, unavailable)
+extension HostingViewRegistry: Sendable {}

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

@@ -0,0 +1,39 @@
+//
+//  HostingViewTransparentBackgroundReason.swift
+//  OpenSwiftUI
+//
+//  Audited for iOS 18.0
+//  Status: Complete
+
+struct HostingViewTransparentBackgroundReason: OptionSet, CustomStringConvertible {
+    var rawValue: UInt32
+
+    static var catalystSidebar = HostingViewTransparentBackgroundReason(rawValue: 1 << 0)
+    static var catalystPresentation = HostingViewTransparentBackgroundReason(rawValue: 1 << 1)
+    static var legacyPresentationSPI = HostingViewTransparentBackgroundReason(rawValue: 1 << 2)
+    static var containerBackground = HostingViewTransparentBackgroundReason(rawValue: 1 << 3)
+    static var listItemBackground = HostingViewTransparentBackgroundReason(rawValue: 1 << 4)
+
+    var description: String {
+        var description = ""
+        if contains(.catalystSidebar) {
+            description.append("catalystSidebar, ")
+        }
+        if contains(.catalystPresentation) {
+            description.append("catalystPresentation, ")
+        }
+        if contains(.legacyPresentationSPI) {
+            description.append("legacyPresentationSPI, ")
+        }
+        if contains(.containerBackground) {
+            description.append("containerBackground, ")
+        }
+        if contains(.listItemBackground) {
+            description.append("listItemBackground, ")
+        }
+        if !description.isEmpty {
+            description.removeLast(2)
+        }
+        return "[\(description)]"
+    }
+}

Sources/OpenSwiftUI/Integration/Hosting/UIKit/Controller/UIHostingController.swift

@@ -0,0 +1,105 @@
+#if os(iOS)
+public import UIKit
+
+@available(macOS, unavailable)
+@available(watchOS, unavailable)
+@MainActor
+@preconcurrency
+open class UIHostingController<Content>: UIViewController where Content : View {
+    var host: _UIHostingView<Content>
+
+    override open dynamic var keyCommands: [UIKeyCommand]? {
+        // TODO
+        nil
+    }
+
+    public init(rootView: Content) {
+        // TODO
+        host = _UIHostingView(rootView: rootView)
+        super.init(nibName: nil, bundle: nil)
+        _commonInit()
+    }
+
+    public init?(coder: NSCoder, rootView: Content) {
+        // TODO
+        host = _UIHostingView(rootView: rootView)
+        super.init(coder: coder)
+        _commonInit()
+    }
+
+    public required init?(coder: NSCoder) {
+        preconditionFailure("init(coder:) must be implemented in a subclass and call super.init(coder:, rootView:)")
+    }
+
+    func _commonInit() {
+        host.viewController = self
+        // toolbar
+        // toolbar.addPreferences(to: ViewGraph)
+        // ...
+        // IsAppleInternalBuild
+    }
+
+    open override func loadView() {
+        view = host
+    }
+
+    public var rootView: Content {
+        get { host.rootView }
+        set { host.rootView = newValue }
+    }
+
+    public var sizingOptions: UIHostingControllerSizingOptions = [] {
+        didSet {
+            sizingOptionsDidChange(from: oldValue)
+        }
+    }
+
+    @_spi(Private)
+    public func setRootView(_ newRootView: Content, transaction: Transaction) {
+        // TODO
+    }
+
+    public func sizeThatFits(in size: CGSize) -> CGSize {
+        host.sizeThatFits(size)
+    }
+
+    public func _render(seconds: Double) {
+        host.render(interval: seconds, targetTimestamp: nil)
+    }
+
+    public func _forEachIdentifiedView(body: (_IdentifiedViewProxy) -> Void) {
+        host._forEachIdentifiedView(body: body)
+    }
+
+    @available(*, deprecated, message: "Use UIHostingController/safeAreaRegions or _UIHostingView/safeAreaRegions")
+    public var _disableSafeArea: Swift.Bool {
+        get {
+            host.explicitSafeAreaInsets == .zero
+        }
+        set {
+            host.explicitSafeAreaInsets = newValue ? .zero : nil
+        }
+    }
+
+    final public var _rendererConfiguration: _RendererConfiguration {
+        get { host._rendererConfiguration }
+        set { host._rendererConfiguration = newValue }
+    }
+
+    final public var _rendererObject: AnyObject? {
+        host._rendererObject
+    }
+
+    func sizingOptionsDidChange(from oldSizingOptions: UIHostingControllerSizingOptions) {
+        // TODO
+    }
+}
+
+@available(macOS, unavailable)
+extension UIHostingController {
+    public var safeAreaRegions: SafeAreaRegions {
+        get { host.safeAreaRegions }
+        set { host.safeAreaRegions = newValue }
+    }
+}
+#endif

Sources/OpenSwiftUI/Integration/Hosting/UIKit/Controller/UIHostingControllerSizingOptions.swift

@@ -0,0 +1,42 @@
+//
+//  UIHostingControllerSizingOptions.swift
+//  OpenSwiftUI
+//
+//  Audited for iOS 18.0
+//  Status: Complete
+
+#if os(iOS)
+
+/// Options for how a hosting controller tracks its content’s size.
+@available(macOS, unavailable)
+public struct UIHostingControllerSizingOptions: OptionSet, Sendable {
+    public let rawValue: Int
+    public init(rawValue: Int) {
+        self.rawValue = rawValue
+    }
+
+    /// The hosting controller tracks its content's ideal size in its
+    /// preferred content size.
+    ///
+    /// Use this option when using a hosting controller with a container view
+    /// controller that requires up-to-date knowledge of the hosting
+    /// controller's ideal size.
+    ///
+    /// - Note: This option comes with a performance cost because it
+    ///   asks for the ideal size of the content using the
+    ///   ``ProposedViewSize/unspecified`` size proposal.
+    public static let preferredContentSize: UIHostingControllerSizingOptions = .init(rawValue: 1 << 0)
+
+    /// The hosting controller's view automatically invalidate its intrinsic
+    /// content size when its ideal size changes.
+    ///
+    /// Use this option when the hosting controller's view is being laid out
+    /// with Auto Layout.
+    ///
+    /// - Note: This option comes with a performance cost because it
+    ///   asks for the ideal size of the content using the
+    ///   ``ProposedViewSize/unspecified`` size proposal.
+    public static let intrinsicContentSize: UIHostingControllerSizingOptions = .init(rawValue: 1 << 1)
+}
+
+#endif