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# CVDisplayLinkSetOutputCallback(_:_:_:)

Sets the renderer output callback function.

```
func CVDisplayLinkSetOutputCallback(_ displayLink: CVDisplayLink, _ callback: CVDisplayLinkOutputCallback?, _ userInfo: UnsafeMutableRawPointer?) -> CVReturn
```

## Parameters

`displayLink`

The display link whose output callback you want to set.

`callback`

The callback function to set for this display link. See [`CVDisplayLinkOutputCallback`](/documentation/CoreVideo/CVDisplayLinkOutputCallback) for more information about implementing this function.

`userInfo`

A pointer to user data.

## Return Value

A Core Video result code. See [Core Video Constants](/documentation/CoreVideo/core-video-constants) for possible values.

## Discussion

The display link invokes this callback whenever it wants you to output a frame.

---

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