---
title: CGDisplayStreamFrameAvailableHandler
framework: coregraphics
role: symbol
role_heading: Type Alias
path: coregraphics/cgdisplaystreamframeavailablehandler
---

# CGDisplayStreamFrameAvailableHandler

A block called when a data stream has a new frame event to process.

## Declaration

```swift
typealias CGDisplayStreamFrameAvailableHandler = (CGDisplayStreamFrameStatus, UInt64, IOSurfaceRef?, CGDisplayStreamUpdate?) -> Void
```

## Discussion

Discussion The handler is called whenever the display stream has updated content to process as well as when other events occur. Each time a new frame is generated, the block receives an IOSurface object that contains the pixel data as well as an update object that describes the frame update. The handler receives the following parameters: If you need to maintain a reference to the surface beyond the lifetime of the handler call, you must call the CFRetain function to retain the surface and the IOSurfaceIncrementUseCount(_:) function to let the display stream know that the frame is not ready for re-use. Once you are finished using the surface you must call the IOSurfaceDecrementUseCount(_:) function and then call the CFRelease function. If you are maintaining a cache of information about the surface (such as a GL texture object created from the surface’s contents), you must not call release it until after you remove it from your cache. You can not depend on the set of surfaces being used by the display stream as being static, so you should remove surfaces from the cache when they haven’t been re-used in a while. If you need to hold onto the metadata beyond the lifetime of the handler call, you must call the CFRetain function on the update reference before the end of the handler. When you are finished with the update, call the call the CFRelease function. This parameter holds NULL when the status parameter’s has any value other than CGDisplayStreamFrameStatus.frameComplete.

## See Also

### Data Types

- [CGButtonCount](coregraphics/cgbuttoncount.md)
- [CGCharCode](coregraphics/cgcharcode.md)
- [CGDirectDisplayID](coregraphics/cgdirectdisplayid.md)
- [CGDisplayBlendFraction](coregraphics/cgdisplayblendfraction.md)
- [CGDisplayConfigRef](coregraphics/cgdisplayconfigref.md)
- [CGDisplayCount](coregraphics/cgdisplaycount.md)
- [CGDisplayErr](coregraphics/cgdisplayerr.md)
- [CGDisplayFadeInterval](coregraphics/cgdisplayfadeinterval.md)
- [CGDisplayFadeReservationToken](coregraphics/cgdisplayfadereservationtoken.md)
- [CGDisplayMode](coregraphics/cgdisplaymode.md)
- [CGDisplayReconfigurationCallBack](coregraphics/cgdisplayreconfigurationcallback.md)
- [CGDisplayReservationInterval](coregraphics/cgdisplayreservationinterval.md)
- [CGDisplayStream](coregraphics/cgdisplaystream.md)
- [CGDisplayStreamUpdate](coregraphics/cgdisplaystreamupdate.md)
- [CGEvent](coregraphics/cgevent.md)