---
title: "customWindowsToEnterFullScreen(for:)"
framework: appkit
role: symbol
role_heading: Instance Method
path: "appkit/nswindowdelegate/customwindowstoenterfullscreen(for:)"
---

# customWindowsToEnterFullScreen(for:)

Called when the window is about to enter full-screen mode.

## Declaration

```swift
@MainActor optional func customWindowsToEnterFullScreen(for window: NSWindow) -> [NSWindow]?
```

## Parameters

- `window`: The window to enter full-screen mode.

## Return Value

Return Value An array of windows to use for the animation to full-screen mode for window; otherwise nil.

## Discussion

Discussion This method lets a window delegate customize the animation when the window is about to enter full-screen mode by providing a custom window or windows containing layers or other effects. If you don’t want to perform custom animation, you can omit the implementation of this method, or it can return nil.

## See Also

### Custom Full-Screen Presentation Animations

- [customWindowsToEnterFullScreen(for:on:)](appkit/nswindowdelegate/customwindowstoenterfullscreen(for:on:).md)
- [window(_:startCustomAnimationToEnterFullScreenWithDuration:)](appkit/nswindowdelegate/window(_:startcustomanimationtoenterfullscreenwithduration:).md)
- [window(_:startCustomAnimationToEnterFullScreenOn:withDuration:)](appkit/nswindowdelegate/window(_:startcustomanimationtoenterfullscreenon:withduration:).md)
- [windowDidFailToEnterFullScreen(_:)](appkit/nswindowdelegate/windowdidfailtoenterfullscreen(_:).md)
- [customWindowsToExitFullScreen(for:)](appkit/nswindowdelegate/customwindowstoexitfullscreen(for:).md)
- [window(_:startCustomAnimationToExitFullScreenWithDuration:)](appkit/nswindowdelegate/window(_:startcustomanimationtoexitfullscreenwithduration:).md)
- [windowDidFailToExitFullScreen(_:)](appkit/nswindowdelegate/windowdidfailtoexitfullscreen(_:).md)