0.1.13

.gitignore

@@ -9,4 +9,5 @@ DerivedData/
 .netrc
 build.sh
 Sources/EngineCore
-Sources/EnginePrivate
+Sources/EnginePrivate
+Sources/EngineCore.xcframework.zip

Example/Example.xcodeproj/project.pbxproj

@@ -341,9 +341,10 @@
 				PRODUCT_BUNDLE_IDENTIFIER = nathantannar.Example;
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = auto;
-				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator macosx";
+				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator macosx xros xrsimulator";
 				SUPPORTS_MACCATALYST = YES;
 				SUPPORTS_MAC_DESIGNED_FOR_IPHONE_IPAD = NO;
+				SUPPORTS_XR_DESIGNED_FOR_IPHONE_IPAD = NO;
 				SWIFT_EMIT_LOC_STRINGS = YES;
 				SWIFT_VERSION = 5.0;
 				TARGETED_DEVICE_FAMILY = "1,2";
@@ -386,9 +387,10 @@
 				PRODUCT_BUNDLE_IDENTIFIER = nathantannar.Example;
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SDKROOT = auto;
-				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator macosx";
+				SUPPORTED_PLATFORMS = "iphoneos iphonesimulator macosx xros xrsimulator";
 				SUPPORTS_MACCATALYST = YES;
 				SUPPORTS_MAC_DESIGNED_FOR_IPHONE_IPAD = NO;
+				SUPPORTS_XR_DESIGNED_FOR_IPHONE_IPAD = NO;
 				SWIFT_EMIT_LOC_STRINGS = YES;
 				SWIFT_VERSION = 5.0;
 				TARGETED_DEVICE_FAMILY = "1,2";

Example/Example/UserInterfaceIdiomExamples.swift

@@ -28,8 +28,8 @@ struct IdiomText: UserInterfaceIdiomContent {
         Text("TV")
     }
 
-    var carBody: some View {
-        Text("Car")
+    var visionBody: some View {
+        Text("Vision")
     }
 }
 

Example/Example/ViewStyleExamples.swift

@@ -410,6 +410,9 @@ struct DoubleLabelStyle: LabeledViewStyle {
             configuration.label
                 .border(Color.yellow, width: 2)
 
+            configuration.label
+                .border(Color.red, width: 2)
+
             LabeledView {
                 configuration.content
             } label: {

Package.swift

@@ -9,7 +9,8 @@ let package = Package(
         .macOS(.v10_15),
         .macCatalyst(.v13),
         .tvOS(.v13),
-        .watchOS(.v6)
+        .watchOS(.v6),
+//        .visionOS(.v1),
     ],
     products: [
         .library(
@@ -25,8 +26,8 @@ let package = Package(
     targets: [
         .binaryTarget(
             name: "EngineCore",
-            url: "https://github.com/nathantannar4/Engine/releases/download/0.1.11/EngineCore.xcframework.zip",
-            checksum: "fab9275d8e2eec39eb498a084b0818f3328078c90805b966816319ef4ad5d85d"
+            url: "https://github.com/nathantannar4/Engine/releases/download/0.1.13/EngineCore.xcframework.zip",
+            checksum: "803b5f45aa79fbaa03d42967434358ec6b609d1d5cbedc6f75d413326d6bc0f9"
         ),
         .target(
             name: "Engine",

README.md

@@ -60,7 +60,7 @@ For some sample code to get started with `Engine`, build and run the included "E
 
 ### Custom View Styles
 
-```
+```swift
 public protocol ViewStyle {
     associatedtype Configuration
     associatedtype Body: View
@@ -86,7 +86,7 @@ A view style makes developing reusable components easier. This can be especially
 
 You can use the `ViewStyle` APIs to make components that share common behavior and/or styling, such as font/colors, while allowing for complete customization of the appearance and layout. For example, this `StepperView` is a component that defaults to `Stepper` but allows for a different custom styling to be used. 
 
-```
+```swift
 // 1. Define the style
 protocol StepperViewStyle: ViewStyle where Configuration == StepperViewStyleConfiguration { }
 
@@ -210,9 +210,84 @@ struct StepperViewBody: ViewStyledView {
 
 [Open Examples](https://github.com/nathantannar4/Engine/blob/main/Example/Example/ViewStyleExamples.swift)
 
-### Variadic Views
+### View Input
+
+```swift
+public protocol ViewAlias: View where Body == Never {
+    associatedtype DefaultBody: View = EmptyView
+    @MainActor @ViewBuilder var defaultBody: DefaultBody { get }
+}
+
+extension View {
 
+    /// Statically type-erases `Source` to be resolved by the ``ViewAlias``.
+    @inlinable
+    public func viewAlias<
+        Alias: ViewAlias,
+        Source: View
+    >(
+        _ : Alias.Type,
+        @ViewBuilder source: () -> Source
+    ) -> some View
+}
 ```
+
+A ``ViewAlias`` is can be defined statically by one of its ancestors. Because ``ViewAlias`` is guaranteed to be static it can be used for type-erasure without the performance impacts associated with `AnyView`.
+
+### View Output
+
+```swift
+@available(iOS 14.0, macOS 11.0, tvOS 14.0, watchOS 7.0, *)
+public protocol ViewOutputKey {
+    associatedtype Content: View = AnyView
+    typealias Value = ViewOutputList<Content>
+    static func reduce(value: inout Value, nextValue: () -> Value)
+}
+
+extension View {
+
+    /// A modifier that writes a `Source` view to a ``ViewOutputKey``
+    @available(iOS 14.0, macOS 11.0, tvOS 14.0, watchOS 7.0, *)
+    @inlinable
+    public func viewOutput<
+        Key: ViewOutputKey,
+        Source: View
+    >(
+        _ : Key.Type,
+        @ViewBuilder source: () -> Source
+    ) -> some View where Key.Content == Source
+```
+
+A `ViewOutputKey` allows for a descendent view to return one or more views to a parent view.  
+
+```swift
+@available(iOS 14.0, macOS 11.0, tvOS 14.0, watchOS 7.0, *)
+public protocol ViewOutputAlias: View where Body == Never {
+    associatedtype Content: View = AnyView
+    associatedtype DefaultBody: View = EmptyView
+    @MainActor @ViewBuilder var defaultBody: DefaultBody { get }
+}
+
+extension View {
+
+    /// Statically defines the `Source` to be resolved by the ``ViewOutputAlias``.
+    @available(iOS 14.0, macOS 11.0, tvOS 14.0, watchOS 7.0, *)
+    @inlinable
+    public func viewOutputAlias<
+        Alias: ViewOutputAlias,
+        Source: View
+    >(
+        _ : Alias.Type,
+        @ViewBuilder source: () -> Source
+    ) -> some View where Alias.Content == Source
+}
+```
+
+A `ViewOutputAlias` is a more streamlined variant of `ViewOutputKey` that only supports returning a single view from a descendent. 
+
+### Variadic Views
+
+```swift
 @frozen
 public struct VariadicViewAdapter<Source: View, Content: View>: View {
 
@@ -232,7 +307,7 @@ A variadic view allows many possibilities with SwiftUI to be unlocked, as it per
 
 You can use `VariadicViewAdapter` to write components like a custom picker view.
 
-```
+```swift
 enum Fruit: Hashable, CaseIterable {
     case apple
     case orange
@@ -284,11 +359,11 @@ struct PickerView<Selection: Hashable, Content: View>: View {
 
 ### Availability
 
-```
+```swift
 public protocol VersionedView: View where Body == Never {
     associatedtype V5Body: View = V4Body
 
-    @available(iOS 17.0, macOS 14.0, tvOS 17.0, watchOS 10.0, *)
+    @available(iOS 17.0, macOS 14.0, tvOS 17.0, watchOS 10.0, xrOS 1.0, *)
     @ViewBuilder var v5Body: V5Body { get }
 
     associatedtype V4Body: View = V3Body
@@ -320,7 +395,7 @@ Supporting multiple release versions for SwiftUI can be tricky. If a modifier or
 
 You can use `VersionedViewModifier` to help adopt newer SwiftUI APIs with less friction. Such as adopting a new view type like `Grid`, while still supporting older iOS versions with a custom grid view; or using new view modifiers which due to the required `if #available(...)` checks can force you to refactor your code.
 
-```
+```swift
 struct ContentView: VersionedView {
     @available(iOS 16.0, macOS 13.0, tvOS 16.0, watchOS 9.0, *)
     var v4Body: some View {
@@ -336,11 +411,21 @@ struct ContentView: VersionedView {
     }
 }
 
-struct UnderlineIfAvailableModifier: VersionedViewModifier {
+struct UnderlineModifier: VersionedViewModifier {
     @available(iOS 16.0, macOS 13.0, tvOS 16.0, watchOS 9.0, *)
     func v4Body(content: Content) -> some View {
         content.underline()
     }
+
+    // Add support for a semi-equivalent version for iOS 13-15
+    func v1Body(content: Content) -> some View {
+        content
+            .background(
+                Rectangle()
+                    .frame(height: 1)
+                    .frame(maxWidth: .infinity, maxHeight: .infinity, alignment: .bottom)
+            )
+    }
 }
 
 struct UnderlineButtonStyle: ButtonStyle {
@@ -366,7 +451,7 @@ struct ContentView: View {
 
 ### Static Conditionals
 
-```
+```swift
 public protocol StaticCondition {
     static var value: Bool { get }
 }
@@ -410,7 +495,7 @@ Should you ever have a modifier or view that is conditional upon a static flag,
 
 You can use `StaticConditionalContent` to gate features or content to Debug or Testflight builds without impacting your production build performance.
 
-```
+```swift
 struct IsDebug: StaticCondition {
     static var value: Bool {
         #if DEBUG

Sources/Engine/Sources/AnyView.swift

@@ -7,27 +7,25 @@ import EngineCore
 
 extension AnyView {
 
-    /// Creates a type-erased view from a type-erased value if that value is also a view
+    /// Creates a type-erased view from a type-erased value if that value is also a `View`
     @_disfavoredOverload
     public init?(_ content: Any) {
-        func project<T>(_ value: T) -> AnyView? {
-            let conformance = ViewProtocolDescriptor.conformance(of: T.self)!
-            var visitor = AnyViewVisitor(input: value)
-            conformance.visit(visitor: &visitor)
-            return visitor.output
-        }
-        guard let view = _openExistential(content, do: project) else {
+        guard let view = AnyView(visiting: content) else {
             return nil
         }
         self = view
     }
 }
 
-private struct AnyViewVisitor<Input>: ViewVisitor {
-    var input: Input
-    var output: AnyView!
+// MARK: - Previews
+
+struct AnyView_Previews: PreviewProvider {
+    static var previews: some View {
+        VStack {
+            AnyView(Optional<String>.none as Any)
 
-    mutating func visit<Content>(type: Content.Type) where Content: View {
-        output = AnyView(unsafeBitCast(input, to: Content.self))
+            let content: Any = Text("Hello, World")
+            AnyView(content)
+        }
     }
 }

Sources/Engine/Sources/ConditionalContent.swift

@@ -53,6 +53,16 @@ extension ConditionalContent: View where TrueContent: View, FalseContent: View {
     }
 }
 
+extension ConditionalContent where TrueContent: View, FalseContent == EmptyView {
+    @inlinable
+    public init(
+        if condition: Bool,
+        @ViewBuilder then: () -> TrueContent
+    ) {
+        self.init(if: condition, then: then, else: { EmptyView() })
+    }
+}
+
 extension ConditionalContent: Equatable where TrueContent: Equatable, FalseContent: Equatable {
     public static func == (lhs: ConditionalContent<TrueContent, FalseContent>, rhs: ConditionalContent<TrueContent, FalseContent>) -> Bool {
         switch (lhs.storage, rhs.storage) {
@@ -65,3 +75,41 @@ extension ConditionalContent: Equatable where TrueContent: Equatable, FalseConte
         }
     }
 }
+
+// MARK: - Previews
+
+struct ConditionalContent_Previews: PreviewProvider {
+    struct Preview: View {
+        @State var condition = true
+
+        var body: some View {
+            VStack {
+                Toggle(
+                    isOn: $condition.animation(.default),
+                    label: { EmptyView() }
+                )
+                .labelsHidden()
+
+                ConditionalContent(if: condition) {
+                    VStack {
+                        content
+                    }
+                } else: {
+                    HStack {
+                        content
+                    }
+                }
+            }
+        }
+
+        @ViewBuilder
+        var content: some View {
+            Text("Hello")
+            Text("World")
+        }
+    }
+
+    static var previews: some View {
+        Preview()
+    }
+}