<!--
{
  "availability" : [
    "macOS: 10.7.0 -"
  ],
  "documentType" : "symbol",
  "framework" : "AppKit",
  "identifier" : "/documentation/AppKit/NSWindowDelegate/customWindowsToEnterFullScreen(for:)",
  "metadataVersion" : "0.1.0",
  "role" : "Instance Method",
  "symbol" : {
    "kind" : "Instance Method",
    "modules" : [
      "AppKit"
    ],
    "preciseIdentifier" : "c:objc(pl)NSWindowDelegate(im)customWindowsToEnterFullScreenForWindow:"
  },
  "title" : "customWindowsToEnterFullScreen(for:)"
}
-->

# customWindowsToEnterFullScreen(for:)

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

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

## Parameters

`window`

The window to enter full-screen mode.

## Return Value

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

## 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`.

---

Copyright &copy; 2026 Apple Inc. All rights reserved. | [Terms of Use](https://www.apple.com/legal/internet-services/terms/site.html) | [Privacy Policy](https://www.apple.com/privacy/privacy-policy)