How to use visual effect view in NSWindow

Set NSVisualEffectView as contentView of NSWindow, and our main view as subview of it. Remember to set frame or autoresizing mask as non-direct content view does not get full size as the window

let mainView = MainView()
    .environment(\.managedObjectContext, coreDataManager.container.viewContext)

window = NSWindow(
    contentRect: .zero,
    styleMask: [.fullSizeContentView],
    backing: .buffered,
    defer: false
)
window.titlebarAppearsTransparent = true
window.center()
window.level = .statusBar
window.setFrameAutosaveName("MyApp")

let visualEffect = NSVisualEffectView()
visualEffect.blendingMode = .behindWindow
visualEffect.state = .active
visualEffect.material = .appearanceBased

let hosting = NSHostingView(rootView: mainView)
window.contentView = visualEffect
visualEffect.addSubview(hosting)
hosting.autoresizingMask = [.width, .height]

Summarize

How to use visual effect view in NSWindow