---
title: "CGGetActiveDisplayList(_:_:_:)"
framework: coregraphics
role: symbol
role_heading: Function
path: "coregraphics/cggetactivedisplaylist(_:_:_:)"
---

# CGGetActiveDisplayList(_:_:_:)

Provides a list of displays that are active for drawing.

## Declaration

```swift
func CGGetActiveDisplayList(_ maxDisplays: UInt32, _ activeDisplays: UnsafeMutablePointer<CGDirectDisplayID>?, _ displayCount: UnsafeMutablePointer<UInt32>?) -> CGError
```

## Parameters

- `maxDisplays`: The size of the activeDisplays array. This value determines the maximum number of displays the list includes.
- `activeDisplays`: A pointer to storage you provide for an array of display IDs. On return, the array contains a list of active displays. If you pass NULL, on return the display count contains the total number of active displays.
- `displayCount`: A pointer to a display count variable you provide. On return, the display count contains the actual number of displays the function added to the activeDisplays array. This value is at most maxDisplays.

## Return Value

Return Value A result code. To interpret the result code, see CGError.

## Discussion

Discussion The first entry in the list of active displays is the main display. In case of mirroring, the first entry is the largest drawable display or, if all are the same size, the display with the greatest pixel depth. Note that when using hardware mirroring between displays, only the primary display is active and appears in the list. When using software mirroring, all the mirrored displays are active and appear in the list. For more information about mirroring, see CGConfigureDisplayMirrorOfDisplay(_:_:_:).

## See Also

### Functions

- [CGAcquireDisplayFadeReservation(_:_:)](coregraphics/cgacquiredisplayfadereservation(_:_:).md)
- [CGAssociateMouseAndMouseCursorPosition(_:)](coregraphics/cgassociatemouseandmousecursorposition(_:).md)
- [CGBeginDisplayConfiguration(_:)](coregraphics/cgbegindisplayconfiguration(_:).md)
- [CGCancelDisplayConfiguration(_:)](coregraphics/cgcanceldisplayconfiguration(_:).md)
- [CGCaptureAllDisplays()](coregraphics/cgcapturealldisplays().md)
- [CGCaptureAllDisplaysWithOptions(_:)](coregraphics/cgcapturealldisplayswithoptions(_:).md)
- [CGCompleteDisplayConfiguration(_:_:)](coregraphics/cgcompletedisplayconfiguration(_:_:).md)
- [CGConfigureDisplayFadeEffect(_:_:_:_:_:_:)](coregraphics/cgconfiguredisplayfadeeffect(_:_:_:_:_:_:).md)
- [CGConfigureDisplayMirrorOfDisplay(_:_:_:)](coregraphics/cgconfiguredisplaymirrorofdisplay(_:_:_:).md)
- [CGConfigureDisplayMode(_:_:_:)](coregraphics/cgconfiguredisplaymode(_:_:_:).md)
- [CGConfigureDisplayOrigin(_:_:_:_:)](coregraphics/cgconfiguredisplayorigin(_:_:_:_:).md)
- [CGConfigureDisplayStereoOperation(_:_:_:_:)](coregraphics/cgconfiguredisplaystereooperation(_:_:_:_:).md)
- [CGConfigureDisplayWithDisplayMode(_:_:_:_:)](coregraphics/cgconfiguredisplaywithdisplaymode(_:_:_:_:).md)
- [CGCursorIsDrawnInFramebuffer()](coregraphics/cgcursorisdrawninframebuffer().md)
- [CGCursorIsVisible()](coregraphics/cgcursorisvisible().md)