SwiftUI implicitRootType Playground

arm64-apple-ios-simulator.swiftinterface

// Extra content to append for your SwiftUICore SDK to use internal package API
extension SwiftUICore.View {
  @available(iOS 18.0, macOS 15.0, tvOS 18.0, watchOS 11.0, visionOS 2.0, *)
  nonisolated public static func makeView(view: _GraphValue<Self>, inputs: _ViewInputs) -> _ViewOutputs

  @available(iOS 18.0, macOS 15.0, tvOS 18.0, watchOS 11.0, visionOS 2.0, *)
  nonisolated public static func makeViewList(view: _GraphValue<Self>, inputs: _ViewListInputs) -> _ViewListOutputs
}

extension SwiftUICore._ViewInputs {
  @available(iOS 18.0, macOS 15.0, tvOS 18.0, watchOS 11.0, visionOS 2.0, *)
  public var implicitRootType: any SwiftUICore._VariadicView.AnyImplicitRoot.Type {
    get
    set
  }
}

extension SwiftUICore._ViewListInputs {
  @available(iOS 18.0, macOS 15.0, tvOS 18.0, watchOS 11.0, visionOS 2.0, *)
  public var implicitRootType: any SwiftUICore._VariadicView.AnyImplicitRoot.Type {
    get
    set
  }
}

@available(iOS 18.0, macOS 15.0, tvOS 18.0, watchOS 11.0, visionOS 2.0, *)
extension SwiftUICore._VariadicView {
  public typealias AnyImplicitRoot = SwiftUICore._VariadicView_AnyImplicitRoot
  public typealias ImplicitRoot = SwiftUICore._VariadicView_ImplicitRoot
  public typealias ImplicitRootVisitor = SwiftUICore._VariadicView_ImplicitRootVisitor
}

@available(iOS 18.0, macOS 15.0, tvOS 18.0, watchOS 11.0, visionOS 2.0, *)
public protocol _VariadicView_AnyImplicitRoot {
  static func visitType<V>(visitor: inout V) where V : SwiftUICore._VariadicView_ImplicitRootVisitor
}

@available(iOS 18.0, macOS 15.0, tvOS 18.0, watchOS 11.0, visionOS 2.0, *)
public protocol _VariadicView_ImplicitRoot : SwiftUICore._VariadicView_AnyImplicitRoot, SwiftUICore._VariadicView_ViewRoot {
  static var implicitRoot: Self { get }
}

@available(iOS 18.0, macOS 15.0, tvOS 18.0, watchOS 11.0, visionOS 2.0, *)
public protocol _VariadicView_ImplicitRootVisitor {
  mutating func visit<R>(type: R.Type) where R : SwiftUICore._VariadicView_ImplicitRoot
}

@available(iOS 18.0, macOS 15.0, tvOS 18.0, watchOS 11.0, visionOS 2.0, *)
extension _HStackLayout: _VariadicView.ImplicitRoot {
    @available(iOS 18.0, macOS 15.0, tvOS 18.0, watchOS 11.0, visionOS 2.0, *)
    public static var implicitRoot: _HStackLayout { .init() }
}

@available(iOS 18.0, macOS 15.0, tvOS 18.0, watchOS 11.0, visionOS 2.0, *)
extension _ZStackLayout: _VariadicView.ImplicitRoot {
    @available(iOS 18.0, macOS 15.0, tvOS 18.0, watchOS 11.0, visionOS 2.0, *)
    public static var implicitRoot: _HStackLayout { .init() }
}

@available(iOS 18.0, macOS 15.0, tvOS 18.0, watchOS 11.0, visionOS 2.0, *)
public final class ViewGraph {
  public static var current: ViewGraph { get }

  public func append<T>(feature: T) where T: ViewGraphFeature
}

@available(iOS 18.0, macOS 15.0, tvOS 18.0, watchOS 11.0, visionOS 2.0, *)
public protocol ViewGraphFeature {
    mutating func modifyViewInputs(inputs: inout _ViewInputs, graph: ViewGraph)
    mutating func modifyViewOutputs(outputs: inout _ViewOutputs, inputs: _ViewInputs, graph: ViewGraph)
    mutating func uninstantiate(graph: ViewGraph)
    mutating func isHiddenForReuseDidChange(graph: ViewGraph)
    mutating func allowsAsyncUpdate(graph: ViewGraph) -> Bool?
    mutating func needsUpdate(graph: ViewGraph) -> Bool
    mutating func update(graph: ViewGraph)
}

@available(iOS 18.0, macOS 15.0, tvOS 18.0, watchOS 11.0, visionOS 2.0, *)
extension SwiftUICore.ViewGraphFeature {
  public mutating func modifyViewInputs(inputs: inout SwiftUICore._ViewInputs, graph: SwiftUICore.ViewGraph)
  public mutating func modifyViewOutputs(outputs: inout SwiftUICore._ViewOutputs, inputs: SwiftUICore._ViewInputs, graph: SwiftUICore.ViewGraph)
  public mutating func uninstantiate(graph: SwiftUICore.ViewGraph)
  public mutating func isHiddenForReuseDidChange(graph: SwiftUICore.ViewGraph)
  #if compiler(>=5.3) && $NoncopyableGenerics
  public mutating func allowsAsyncUpdate(graph: SwiftUICore.ViewGraph) -> Swift.Bool?
  #else
  public mutating func allowsAsyncUpdate(graph: SwiftUICore.ViewGraph) -> Swift.Bool?
  #endif
  public mutating func needsUpdate(graph: SwiftUICore.ViewGraph) -> Swift.Bool
  public mutating func update(graph: SwiftUICore.ViewGraph)
}

ContentView.swift

// Usage: ViewGraph.current.append(feature: HStackImplicitFeature())
struct HStackImplicitFeature: ViewGraphFeature {
    func modifyViewInputs(inputs: inout _ViewInputs, graph: ViewGraph) {
        inputs.implicitRootType = _HStackLayout.self
    }
}

struct ContentView: View {
    var body: some View {
        ChildView1()
        // ChildView2()
    }
}

struct ChildView1: View {
    @State private var show = false

    var body: some View {
        Color.red
        Color.blue
    }

    static func _makeView(view: _GraphValue<Self>, inputs: _ViewInputs) -> _ViewOutputs {
        var inputs = inputs
        inputs.implicitRootType = _HStackLayout.self
        return makeView(view: view, inputs: inputs)
    }

    static func _makeViewList(view: _GraphValue<Self>, inputs: _ViewListInputs) -> _ViewListOutputs {
        var inputs = inputs
        inputs.implicitRootType = _HStackLayout.self
        return makeViewList(view: view, inputs: inputs)
    }
}

struct ChildView2: View {
    @State private var show = false

    var body: some View {
        Color.red.opacity(0.5)
        Color.blue.opacity(0.5)
    }

    static func _makeView(view: _GraphValue<Self>, inputs: _ViewInputs) -> _ViewOutputs {
        var inputs = inputs
        inputs.implicitRootType = _ZStackLayout.self
        return makeView(view: view, inputs: inputs)
    }

    static func _makeViewList(view: _GraphValue<Self>, inputs: _ViewListInputs) -> _ViewListOutputs {
        var inputs = inputs
        inputs.implicitRootType = _ZStackLayout.self
        return makeViewList(view: view, inputs: inputs)
    }
}

#Preview {
    ContentView()
}

Originally posted in https://x.com/KyleSwifter/status/1977747002604630157

Preview: