struct ContentView: View {
    @Binding var document: MyDocument
    @Environment(\.undoManager) var undoManager
    @State private var hasUnsavedChanges = false
    
    var body: some View {
        TextEditor(text: $document.content)
            .onChange(of: document.content) { _, newValue in
                hasUnsavedChanges = true
                undoManager?.registerUndo(withTarget: document) { doc in
                    doc.content = document.content
                }
            }
            .toolbar {
                ToolbarItem(placement: .status) {
                    if hasUnsavedChanges {
                        Label("Unsaved Changes", systemImage: "circle.fill")
                            .foregroundColor(.orange)
                    }
                }
            }
    }
}