Add UnaryLayout and LayoutProxy (#299)

* Update OG dependency

* Add LayoutProxy implementation

* Update documentation for LayoutProxy

* Add UnaryLayout

* Add OG dependency to fix link issue

* Fix Linux build issue

Author: Kyle-Ye

Package.resolved

@@ -7,7 +7,7 @@
       "location" : "https://github.com/OpenSwiftUIProject/DarwinPrivateFrameworks.git",
       "state" : {
         "branch" : "main",
-        "revision" : "2ba5179547b9cefddfd304bbda6d0d0704946fe3"
+        "revision" : "81e34b38e1bd8b2729cdc201c4c0f06746dd87b0"
       }
     },
     {
@@ -25,7 +25,7 @@
       "location" : "https://github.com/OpenSwiftUIProject/OpenGraph",
       "state" : {
         "branch" : "main",
-        "revision" : "732ce4507120fbee7bc43ec0c8407f4c3d431811"
+        "revision" : "433aa3a58e5c871461328971cacb7bd09f519d9a"
       }
     },
     {

Sources/OpenSwiftUICore/Layout/LayoutProxy.swift

@@ -0,0 +1,245 @@
+//
+//  LayoutProxy.swift
+//  OpenSwiftUICore
+//
+//  Audited for iOS 18.0
+//  Status: Complete
+
+package import Foundation
+package import OpenGraphShims
+
+/// A collection of attributes that can be applied to layout calculations.
+///
+/// `LayoutProxyAttributes` stores optional references to a layout computer and a view trait list,
+/// which are used to compute layouts and access view traits during layout operations.
+package struct LayoutProxyAttributes: Equatable {
+    /// The layout computer used to calculate sizes and positions.
+    @OptionalAttribute
+    var layoutComputer: LayoutComputer?
+
+    /// The list of view traits that affect layout behavior.
+    @OptionalAttribute
+    var traitList: (any ViewList)?
+
+    /// Creates layout proxy attributes with the specified layout computer and traits list.
+    ///
+    /// - Parameters:
+    ///   - layoutComputer: The optional attribute containing a layout computer.
+    ///   - traitsList: The optional attribute containing view traits.
+    package init(layoutComputer: OptionalAttribute<LayoutComputer>, traitsList: OptionalAttribute<any ViewList>) {
+        _layoutComputer = layoutComputer
+        _traitList = traitsList
+    }
+
+    /// Creates layout proxy attributes with only traits.
+    ///
+    /// - Parameter traitsList: The optional attribute containing view traits.
+    package init(traitsList: OptionalAttribute<any ViewList>) {
+        _layoutComputer = OptionalAttribute()
+        _traitList = traitsList
+    }
+
+    /// Creates layout proxy attributes with only a layout computer.
+    ///
+    /// - Parameter layoutComputer: The optional attribute containing a layout computer.
+    package init(layoutComputer: OptionalAttribute<LayoutComputer>) {
+        _layoutComputer = layoutComputer
+        _traitList = OptionalAttribute()
+    }
+
+    /// Creates empty layout proxy attributes with no layout computer or traits.
+    package init() {
+        _layoutComputer = OptionalAttribute()
+        _traitList = OptionalAttribute()
+    }
+
+    /// Determines if this collection of attributes is empty.
+    ///
+    /// Returns `true` if neither the layout computer nor the trait list is set.
+    package var isEmpty: Bool {
+        $layoutComputer == nil && $traitList == nil
+    }
+}
+
+/// A proxy object used to perform layout calculations for views.
+///
+/// `LayoutProxy` provides an interface to compute sizes, dimensions, and positions
+/// of views during the layout process. It combines layout computers and view traits
+/// to determine the final layout characteristics of a view.
+package struct LayoutProxy: Equatable {
+    /// The rule context used to resolve attribute values.
+    var context: AnyRuleContext
+
+    /// The attributes that define the layout behavior.
+    var attributes: LayoutProxyAttributes
+
+    /// Creates a layout proxy with the specified context and attributes.
+    ///
+    /// - Parameters:
+    ///   - context: The rule context used to resolve attribute values.
+    ///   - attributes: The attributes that define the layout behavior.
+    package init(context: AnyRuleContext, attributes: LayoutProxyAttributes) {
+        self.context = context
+        self.attributes = attributes
+    }
+
+    /// Creates a layout proxy with the specified context and layout computer.
+    ///
+    /// - Parameters:
+    ///   - context: The rule context used to resolve attribute values.
+    ///   - layoutComputer: The optional layout computer to use for calculations.
+    package init(context: AnyRuleContext, layoutComputer: Attribute<LayoutComputer>?) {
+        self.context = context
+        self.attributes = LayoutProxyAttributes(layoutComputer: .init(layoutComputer))
+    }
+
+    /// The layout computer to use for layout calculations.
+    ///
+    /// If no layout computer is explicitly provided, returns the default layout computer.
+    package var layoutComputer: LayoutComputer {
+        guard let layoutComputer = attributes.$layoutComputer else {
+            return .defaultValue
+        }
+        return context[layoutComputer]
+    }
+
+    /// The collection of view traits associated with this layout proxy.
+    ///
+    /// Returns `nil` if no trait list is available.
+    package var traits: ViewTraitCollection? {
+        guard let traitList = attributes.$traitList else {
+            return nil
+        }
+        return context[traitList].traits
+    }
+
+    /// Accesses a specific trait value by its key type.
+    ///
+    /// - Parameter key: The trait key type to look up.
+    /// - Returns: The value for the specified trait key, or the default value if the trait is not present.
+    package subscript<K>(key: K.Type) -> K.Value where K: _ViewTraitKey {
+        traits.map { $0[key] } ?? K.defaultValue
+    }
+
+    /// Returns the spacing configuration for this layout.
+    ///
+    /// - Returns: The spacing configuration derived from the layout computer.
+    package func spacing() -> Spacing {
+        layoutComputer.spacing()
+    }
+
+    /// Calculates the ideal size for the view without any specific constraints.
+    ///
+    /// - Returns: The ideal size as determined by the layout computer.
+    package func idealSize() -> CGSize {
+        size(in: .unspecified)
+    }
+
+    /// Calculates the size that fits within the given proposed size.
+    ///
+    /// - Parameter proposedSize: The size constraints to consider.
+    /// - Returns: The calculated size that fits within the constraints.
+    package func size(in proposedSize: _ProposedSize) -> CGSize {
+        layoutComputer.sizeThatFits(proposedSize)
+    }
+
+    /// Calculates the length that fits within the given proposal along a specific axis.
+    ///
+    /// - Parameters:
+    ///   - proposal: The size constraints to consider.
+    ///   - direction: The axis along which to calculate the length.
+    /// - Returns: The calculated length that fits within the constraints.
+    package func lengthThatFits(_ proposal: _ProposedSize, in direction: Axis) -> CGFloat {
+        layoutComputer.lengthThatFits(proposal, in: direction)
+    }
+
+    /// Calculates the view dimensions within the given proposed size.
+    ///
+    /// - Parameter proposedSize: The size constraints to consider.
+    /// - Returns: The calculated dimensions including size and alignment guides.
+    package func dimensions(in proposedSize: _ProposedSize) -> ViewDimensions {
+        let computer = layoutComputer
+        return ViewDimensions(
+            guideComputer: computer,
+            size: computer.sizeThatFits(proposedSize),
+            proposal: _ProposedSize(
+                width: proposedSize.width ?? .nan,
+                height: proposedSize.height ?? .nan
+            )
+        )
+    }
+
+    /// Calculates the final geometry of a view at a specific placement within a parent.
+    ///
+    /// - Parameters:
+    ///   - p: The placement defining position and proposed size.
+    ///   - parentSize: The size of the parent container.
+    ///   - layoutDirection: The layout direction (left-to-right or right-to-left).
+    /// - Returns: The final view geometry including position and dimensions.
+    package func finallyPlaced(at p: _Placement, in parentSize: CGSize, layoutDirection: LayoutDirection) -> ViewGeometry {
+        let dimensions = dimensions(in: p.proposedSize_)
+        var geometry = ViewGeometry(
+            placement: p,
+            dimensions: dimensions
+        )
+        geometry.finalizeLayoutDirection(layoutDirection, parentSize: parentSize)
+        return geometry
+    }
+
+    /// Returns the explicit alignment for a specific alignment key at the given size.
+    ///
+    /// - Parameters:
+    ///   - k: The alignment key to measure.
+    ///   - mySize: The size at which to measure the alignment.
+    /// - Returns: The explicit alignment position, or `nil` if not explicitly defined.
+    package func explicitAlignment(_ k: AlignmentKey, at mySize: ViewSize) -> CGFloat? {
+        layoutComputer.explicitAlignment(k, at: mySize)
+    }
+
+    /// The layout priority of the view, which influences layout decisions.
+    ///
+    /// Higher values indicate higher priority during layout calculations.
+    package var layoutPriority: Double {
+        layoutComputer.layoutPriority()
+    }
+
+    /// Indicates whether the view ignores automatic padding applied by container views.
+    package var ignoresAutomaticPadding: Bool {
+        layoutComputer.ignoresAutomaticPadding()
+    }
+
+    /// Indicates whether the view requires spacing projection during layout.
+    package var requiresSpacingProjection: Bool {
+        layoutComputer.requiresSpacingProjection()
+    }
+}
+
+/// A collection of layout proxies that can be accessed by index.
+///
+/// `LayoutProxyCollection` provides random access to a collection of layout proxies,
+/// each representing a different view or component in a layout hierarchy.
+package struct LayoutProxyCollection: RandomAccessCollection {
+    /// The rule context used to resolve attribute values.
+    var context: AnyRuleContext
+
+    /// The attributes for each layout proxy in the collection.
+    var attributes: [LayoutProxyAttributes]
+
+    /// Creates a layout proxy collection with the specified context and attributes.
+    ///
+    /// - Parameters:
+    ///   - context: The rule context used to resolve attribute values.
+    ///   - attributes: The array of attributes for each layout proxy.
+    package init(context: AnyRuleContext, attributes: [LayoutProxyAttributes]) {
+        self.context = context
+        self.attributes = attributes
+    }
+
+    package var startIndex: Int { .zero }
+
+    package var endIndex: Int { attributes.endIndex }
+
+    package subscript(index: Int) -> LayoutProxy {
+        LayoutProxy(context: context, attributes: attributes[index])
+    }
+}

Sources/OpenSwiftUICore/Layout/Stack/LayoutPriorityLayout.swift

@@ -5,6 +5,8 @@
 //  Audited for iOS 18.0
 //  Status: WIP
 
+package import Foundation
+
 extension View {
     /// Sets the priority by which a parent layout should apportion space to
     /// this child.
@@ -56,18 +58,17 @@ package struct LayoutPriorityTraitKey: _ViewTraitKey {
 @available(*, unavailable)
 extension LayoutPriorityTraitKey: Sendable {}
 
-// FIXME
-protocol UnaryLayout: ViewModifier {
-    static func makeViewImpl(
-        modifier: _GraphValue<Self>,
-        inputs: _ViewInputs,
-        body: @escaping (_Graph, _ViewInputs) -> _ViewOutputs
-    ) -> _ViewOutputs
-}
-
 // FIXME
 package struct LayoutPriorityLayout: UnaryLayout {
-    static func makeViewImpl(modifier: _GraphValue<LayoutPriorityLayout>, inputs: _ViewInputs, body: @escaping (_Graph, _ViewInputs) -> _ViewOutputs) -> _ViewOutputs {
+    package func placement(of child: LayoutProxy, in context: PlacementContext) -> _Placement {
+        preconditionFailure("TODO")
+    }
+    
+    package func sizeThatFits(in proposedSize: _ProposedSize, context: SizeAndSpacingContext, child: LayoutProxy) -> CGSize {
+        preconditionFailure("TODO")
+    }
+    
+    package static func makeViewImpl(modifier: _GraphValue<LayoutPriorityLayout>, inputs: _ViewInputs, body: @escaping (_Graph, _ViewInputs) -> _ViewOutputs) -> _ViewOutputs {
         .init()
     }
 }

Sources/OpenSwiftUICore/Layout/UnaryLayout.swift

@@ -0,0 +1,50 @@
+//
+//  UnaryLayout.swift
+//  OpenSwiftUICore
+//
+//  Audited for iOS 18.0
+//  Status: WIP
+
+package import Foundation
+
+package protocol UnaryLayout: Animatable, MultiViewModifier, PrimitiveViewModifier {
+    associatedtype PlacementContextType = PlacementContext
+
+    func spacing(in context: SizeAndSpacingContext, child: LayoutProxy) -> Spacing
+
+    func placement(of child: LayoutProxy, in context: PlacementContextType) -> _Placement
+
+    func sizeThatFits(in proposedSize: _ProposedSize, context: SizeAndSpacingContext, child: LayoutProxy) -> CGSize
+
+    func layoutPriority(child: LayoutProxy) -> Double
+
+    func ignoresAutomaticPadding(child: LayoutProxy) -> Bool
+
+    static func makeViewImpl(
+        modifier: _GraphValue<Self>,
+        inputs: _ViewInputs,
+        body: @escaping (_Graph, _ViewInputs) -> _ViewOutputs
+    ) -> _ViewOutputs
+}
+
+extension UnaryLayout {
+    package func layoutPriority(child: LayoutProxy) -> Double {
+        child.layoutPriority
+    }
+
+    package func ignoresAutomaticPadding(child: LayoutProxy) -> Bool {
+        false
+    }
+
+    nonisolated public static func _makeView(
+        modifier: _GraphValue<Self>,
+        inputs: _ViewInputs,
+        body: @escaping (_Graph, _ViewInputs) -> _ViewOutputs
+    ) -> _ViewOutputs {
+        makeViewImpl(modifier: modifier, inputs: inputs, body: body)
+    }
+
+    package func spacing(in context: SizeAndSpacingContext, child: LayoutProxy) -> Spacing {
+        child.spacing()
+    }
+}

Sources/OpenSwiftUICore/OpenGraph/Attribute/AsyncAttribute.swift

@@ -27,9 +27,3 @@ extension Attribute {
         }
     }
 }
-
-// FIXME: Add OGChangedValueFlagsRequiresMainThread in OpenGraph
-
-extension OGChangedValueFlags {
-    static let requiresMainThread = Self(rawValue: 2)
-}