feat(layout): add coordinate space modifiers

Sources/OpenSwiftUI/Layout/Modifier/CoordinateSpaceModifier.swift

@@ -0,0 +1,209 @@
+//
+//  CoordinateSpaceModifier.swift
+//  OpenSwiftUI
+//
+//  Audited for 6.5.4
+//  Status: Complete
+//  ID: AC3D921589C9B46E7A4620E6FB24D937 (SwiftUI)
+
+import Foundation
+import OpenAttributeGraphShims
+@_spi(ForOpenSwiftUIOnly)
+public import OpenSwiftUICore
+
+// MARK: - _CoordinateSpaceModifier
+
+@available(OpenSwiftUI_v1_0, *)
+@frozen
+public struct _CoordinateSpaceModifier<Name>: ViewModifier, ViewInputsModifier, Equatable where Name: Hashable {
+    public var name: Name
+
+    @inlinable
+    public init(name: Name) {
+        self.name = name
+    }
+
+    nonisolated public static func _makeViewInputs(modifier: _GraphValue<Self>, inputs: inout _ViewInputs) {
+        inputs.transform = Attribute(CoordinateSpaceTransform(
+            modifier: modifier.value,
+            transform: inputs.transform,
+            position: inputs.animatedPosition(),
+            size: inputs.animatedCGSize()
+        ))
+    }
+
+    public typealias Body = Never
+}
+
+@available(*, unavailable)
+extension _CoordinateSpaceModifier: Sendable {}
+
+// MARK: - View + CoordinateSpace
+
+@available(OpenSwiftUI_v1_0, *)
+extension View {
+    /// Assigns a name to the view's coordinate space, so other code can operate
+    /// on dimensions like points and sizes relative to the named space.
+    ///
+    /// Use `coordinateSpace(name:)` to allow another function to find and
+    /// operate on a view and operate on dimensions relative to that view.
+    ///
+    /// The example below demonstrates how a nested view can find and operate on
+    /// its enclosing view's coordinate space:
+    ///
+    ///     struct ContentView: View {
+    ///         @State private var location = CGPoint.zero
+    ///
+    ///         var body: some View {
+    ///             VStack {
+    ///                 Color.red.frame(width: 100, height: 100)
+    ///                     .overlay(circle)
+    ///                 Text("Location: \(Int(location.x)), \(Int(location.y))")
+    ///             }
+    ///             .coordinateSpace(name: "stack")
+    ///         }
+    ///
+    ///         var circle: some View {
+    ///             Circle()
+    ///                 .frame(width: 25, height: 25)
+    ///                 .gesture(drag)
+    ///                 .padding(5)
+    ///         }
+    ///
+    ///         var drag: some Gesture {
+    ///             DragGesture(coordinateSpace: .named("stack"))
+    ///                 .onChanged { info in location = info.location }
+    ///         }
+    ///     }
+    ///
+    /// Here, the ``VStack`` in the `ContentView` named “stack” is composed of a
+    /// red frame with a custom ``Circle`` view ``View/overlay(_:alignment:)``
+    /// at its center.
+    ///
+    /// The `circle` view has an attached ``DragGesture`` that targets the
+    /// enclosing VStack's coordinate space. As the gesture recognizer's closure
+    /// registers events inside `circle` it stores them in the shared `location`
+    /// state variable and the ``VStack`` displays the coordinates in a ``Text``
+    /// view.
+    ///
+    /// ![A screenshot showing an example of finding a named view and tracking
+    /// relative locations in that view.](OpenSwiftUI-View-coordinateSpace)
+    ///
+    /// - Parameter name: A name used to identify this coordinate space.
+    @available(iOS, deprecated: 100000.0, message: "use coordinateSpace(_:) instead")
+    @available(macOS, deprecated: 100000.0, message: "use coordinateSpace(_:) instead")
+    @available(tvOS, deprecated: 100000.0, message: "use coordinateSpace(_:) instead")
+    @available(watchOS, deprecated: 100000.0, message: "use coordinateSpace(_:) instead")
+    @available(visionOS, deprecated: 100000.0, message: "use coordinateSpace(_:) instead")
+    @inlinable
+    nonisolated public func coordinateSpace<T>(name: T) -> some View where T: Hashable {
+        modifier(_CoordinateSpaceModifier(name: name))
+    }
+}
+
+@available(OpenSwiftUI_v5_0, *)
+extension View {
+    /// Assigns a name to the view's coordinate space, so other code can operate
+    /// on dimensions like points and sizes relative to the named space.
+    ///
+    /// Use `coordinateSpace(_:)` to allow another function to find and
+    /// operate on a view and operate on dimensions relative to that view.
+    ///
+    /// The example below demonstrates how a nested view can find and operate on
+    /// its enclosing view's coordinate space:
+    ///
+    ///     struct ContentView: View {
+    ///         @State private var location = CGPoint.zero
+    ///
+    ///         var body: some View {
+    ///             VStack {
+    ///                 Color.red.frame(width: 100, height: 100)
+    ///                     .overlay(circle)
+    ///                 Text("Location: \(Int(location.x)), \(Int(location.y))")
+    ///             }
+    ///             .coordinateSpace(.named("stack"))
+    ///         }
+    ///
+    ///         var circle: some View {
+    ///             Circle()
+    ///                 .frame(width: 25, height: 25)
+    ///                 .gesture(drag)
+    ///                 .padding(5)
+    ///         }
+    ///
+    ///         var drag: some Gesture {
+    ///             DragGesture(coordinateSpace: .named("stack"))
+    ///                 .onChanged { info in location = info.location }
+    ///         }
+    ///     }
+    ///
+    /// Here, the ``VStack`` in the `ContentView` named “stack” is composed of a
+    /// red frame with a custom ``Circle`` view ``View/overlay(_:alignment:)``
+    /// at its center.
+    ///
+    /// The `circle` view has an attached ``DragGesture`` that targets the
+    /// enclosing VStack's coordinate space. As the gesture recognizer's closure
+    /// registers events inside `circle` it stores them in the shared `location`
+    /// state variable and the ``VStack`` displays the coordinates in a ``Text``
+    /// view.
+    ///
+    /// ![A screenshot showing an example of finding a named view and tracking
+    /// relative locations in that view.](OpenSwiftUI-View-coordinateSpace)
+    ///
+    /// - Parameter name: A name used to identify this coordinate space.
+    nonisolated public func coordinateSpace(_ name: NamedCoordinateSpace) -> some View {
+        modifier(CoordinateSpaceNameModifier(name: name))
+    }
+}
+
+// MARK: - CoordinateSpaceTransform
+
+private struct CoordinateSpaceTransform<Name>: Rule, AsyncAttribute where Name: Hashable {
+    @Attribute var modifier: _CoordinateSpaceModifier<Name>
+    @Attribute var transform: ViewTransform
+    @Attribute var position: CGPoint
+    @Attribute var size: CGSize
+
+    var value: ViewTransform {
+        var transform = transform
+        transform.appendPosition(position)
+        transform.appendSizedSpace(name: modifier.name, size: size)
+        return transform
+    }
+}
+
+// MARK: - CoordinateSpaceNameModifier
+
+private struct CoordinateSpaceNameModifier: PrimitiveViewModifier, ViewInputsModifier {
+    var name: NamedCoordinateSpace
+
+    static func _makeViewInputs(modifier: _GraphValue<Self>, inputs: inout _ViewInputs) {
+        inputs.transform = Attribute(CoordinateSpaceNameTransform(
+            modifier: modifier.value,
+            transform: inputs.transform,
+            position: inputs.animatedPosition(),
+            size: inputs.animatedCGSize()
+        ))
+    }
+}
+
+// MARK: - CoordinateSpaceNameTransform
+
+private struct CoordinateSpaceNameTransform: Rule, AsyncAttribute {
+    @Attribute var modifier: CoordinateSpaceNameModifier
+    @Attribute var transform: ViewTransform
+    @Attribute var position: CGPoint
+    @Attribute var size: CGSize
+
+    var value: ViewTransform {
+        var transform = transform
+        transform.appendPosition(position)
+        switch modifier.name.name {
+        case let .name(name):
+            transform.appendSizedSpace(name: name, size: size)
+        case let .id(id):
+            transform.appendSizedSpace(id: id, size: size)
+        }
+        return transform
+    }
+}