Hi!
I would like to overlay a macOS application window above all windows, even when moving spaces or moving to a fullscreen app, similar in function to the DropOver app for macOS.
What I have tried:
Overwriting the default app delegate in SwiftUI and creating the NSWindow myself.
Then setting the window.collectionBehavior to [.canJoinAllApplications, .canJoinAllSpaces, .fullScreenAuxiliary] and the window.level to .floating or .statusBar. This works for moving between Spaces, but still does not display above apps in fullscreen mode.
I also registered a notification observer for NSWorkspace.activeSpaceDidChangeNotification, where I call window.orderFrontRegardless() to always have my window frontmost. Still not displaying above fullscreen apps.
What am I missing to make this work?
Best regards
Your collectionBehavior is close — canJoinAllApplications is the right option for spanning other apps' Spaces — but two other pieces are missing for floating above full-screen apps:
1. Accessory activation policy. macOS doesn't layer regular foreground apps above other apps' full-screen Spaces. Overlay utilities like DropOver use NSApplicationActivationPolicyAccessory, which removes the Dock icon and app menu bar (most overlay utilities add a menu bar status item in their place) and lets the app's windows appear above full-screen content from other apps. In your app delegate's applicationDidFinishLaunching:
NSApp.setActivationPolicy(.accessory)
2. NSPanel with .nonactivatingPanel. An NSWindow activates its app when ordered front, which can cause a full-screen app to exit its Space. An NSPanel with the .nonactivatingPanel style mask doesn't.
Full panel setup:
let panel = NSPanel(
contentRect: NSRect(x: 200, y: 200, width: 260, height: 140),
styleMask: [.nonactivatingPanel, .titled, .closable],
backing: .buffered,
defer: false
)
panel.isFloatingPanel = true
panel.hidesOnDeactivate = false
panel.level = .screenSaver
panel.collectionBehavior = [
.canJoinAllSpaces,
.canJoinAllApplications,
.fullScreenAuxiliary,
.stationary
]
panel.orderFrontRegardless()
A couple of notes:
- You need
.screenSaver(level 1000) —.floating(3) and.statusBar(25) both sit below full-screen content. - With this configuration, you can remove your
activeSpaceDidChangeNotificationobserver. The collection behavior keeps the panel visible on every Space — including other apps' full-screen Spaces — so the manualorderFrontRegardless()on space change is unnecessary.
I tested this combination in macOS 26 against Safari, QuickTime Player, and a YouTube video in full screen, and the panel stayed on top in all three cases.
