---
title: USDPreviewSession.ChangeListDelegate
framework: spatialpreview
role: symbol
role_heading: Protocol
platforms: [macOS 27.0+]
path: spatialpreview/usdpreviewsession/changelistdelegate
---

# USDPreviewSession.ChangeListDelegate

A protocol to provide shared undo/redo tracking in a USDPreviewSession.

## Declaration

```swift
@MainActor protocol ChangeListDelegate : AnyObject
```

## Topics

### Instance Methods

- [didApplyChanges(instanceIdentifier:operationIdentifier:)](spatialpreview/usdpreviewsession/changelistdelegate/didapplychanges(instanceidentifier:operationidentifier:).md)
- [onRedoRequest()](spatialpreview/usdpreviewsession/changelistdelegate/onredorequest().md)
- [onUndoRequest()](spatialpreview/usdpreviewsession/changelistdelegate/onundorequest().md)
- [willApplyChanges(instanceIdentifier:operationIdentifier:)](spatialpreview/usdpreviewsession/changelistdelegate/willapplychanges(instanceidentifier:operationidentifier:).md)