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node_modules/react-native-screens/ios/gamma/split-view/RNSSplitViewNavigationController.swift

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+import Foundation
+import UIKit
+
+/// @brief A protocol that observes origin changes in a RNSSplitViewNavigationController’s view frame.
+///
+/// The subscriber will be notified when the view's origin changes.
+protocol RNSSplitViewNavigationControllerViewFrameObserver: AnyObject {
+  func splitViewNavCtrlViewDidChangeFrameOrigin(
+    _ splitViewNavCtrl: RNSSplitViewNavigationController)
+}
+
+/// @class RNSSplitViewNavigationController
+/// @brief A subclass of UINavigationController, creates a view that wraps view associated with RNSSplitViewScreenController.
+///
+/// This subclass is responsible for tracking when the underlying view's frame origin changes,
+/// allowing for syncing the ShadowTree layout.
+///
+/// It observes origin changes via key-value observer and notifies a delegate.
+@objc
+public class RNSSplitViewNavigationController: UINavigationController {
+  private var viewFrameObservation: NSKeyValueObservation?
+  weak var viewFrameOriginChangeObserver: RNSSplitViewNavigationControllerViewFrameObserver?
+
+  ///
+  /// @brief Called after the view controller’s view has been loaded.
+  ///
+  /// Sets up a frame-origin Key-Value Observer to monitor view position changes and propagate them via delegate to RNSSplitViewHostController.
+  ///
+  override public func viewDidLoad() {
+    super.viewDidLoad()
+
+    viewFrameObservation?.invalidate()
+    viewFrameObservation = self.view.observe(\.frame, options: [.old, .new]) {
+      [weak self] (view, change) in
+      guard let oldFrame = change.oldValue, let newFrame = change.newValue else { return }
+
+      if oldFrame.origin != newFrame.origin {
+        self?.onViewOriginChange()
+      }
+    }
+  }
+
+  private func onViewOriginChange() {
+    viewFrameOriginChangeObserver?.splitViewNavCtrlViewDidChangeFrameOrigin(self)
+  }
+}