Add ResponderNode

Sources/OpenSwiftUI/EventHandling/Focus/FocusStore.swift

@@ -1,3 +1,6 @@
+@_spi(ForOpenSwiftUIOnly)
+import OpenSwiftUICore
+
 struct FocusStore {
     var seed: VersionSeed
     var focusedResponders: ContiguousArray<ResponderNode>

Sources/OpenSwiftUICore/Event/Event_TODO.swift

@@ -1,7 +1,5 @@
 // FIXME
 
-package class ResponderNode {}
-
 package struct ExclusiveGesture<A, B>: PrimitiveGesture {}
 
 package struct _MapGesture<Content, Value>: PrimitiveGesture where Content: Gesture {

Sources/OpenSwiftUICore/Event/Responder/ResponderNode.swift

@@ -0,0 +1,72 @@
+//
+//  ResponderNode.swift
+//  OpenSwiftUICore
+//
+//  Status: Complete
+
+// MARK: - ResponderNode [6.5.4]
+
+@_spi(ForOpenSwiftUIOnly)
+@available(OpenSwiftUI_v6_0, *)
+open class ResponderNode {
+    public init() {}
+
+    open var nextResponder: ResponderNode? {
+        preconditionFailure("")
+    }
+
+    open func bindEvent(_ event: any EventType) -> ResponderNode? {
+        nil
+    }
+
+    @discardableResult
+    open func visit(applying visitor: (ResponderNode) -> ResponderVisitorResult) -> ResponderVisitorResult {
+        visitor(self)
+    }
+
+    open func makeGesture(inputs: _GestureInputs) -> _GestureOutputs<Void> {
+        _GestureOutputs(phase: inputs.intern(.failed, id: .failedValue))
+    }
+
+    open func resetGesture() {}
+
+    final package var sequence: some Sequence<ResponderNode> {
+        Swift.sequence(first: self) { $0.nextResponder }
+    }
+
+    final package func isDescendant(of responder: ResponderNode) -> Bool {
+        var current: ResponderNode? = self
+        while let currentResponder = current {
+            guard currentResponder !== responder else {
+                return true
+            }
+            current = currentResponder.nextResponder
+        }
+        return false
+    }
+
+    final package func firstAncestor<T>(ofType type: T.Type = T.self) -> T? {
+        Swift.sequence(first: self) { $0.nextResponder }
+            .first(ofType: type)
+    }
+}
+
+@_spi(ForOpenSwiftUIOnly)
+@available(*, unavailable)
+extension ResponderNode: Sendable {}
+
+// MARK: - ResponderVisitorResult [6.5.4] [WIP]
+
+@_spi(ForOpenSwiftUIOnly)
+@available(OpenSwiftUI_v6_0, *)
+public enum ResponderVisitorResult: Equatable {
+    case next
+
+    case skipToNextSibling
+
+    case cancel
+}
+
+@_spi(ForOpenSwiftUIOnly)
+@available(*, unavailable)
+extension ResponderVisitorResult: Sendable {}