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# CGDisplayIsAlwaysInMirrorSet(_:)

Returns a Boolean value indicating whether a display is always in a mirroring set.

```
func CGDisplayIsAlwaysInMirrorSet(_ display: CGDirectDisplayID) -> boolean_t
```

## Parameters

`display`

The identifier of the display to be accessed.

## Return Value

If `true`, the specified display is in a mirroring set and cannot be removed from this set.

## Discussion

Some hardware configurations support the connection of auxiliary displays that always mirror the main display and therefore cannot be removed from the mirroring set to which they belong.

---

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