This sample project demonstrates a custom NSWindowController that can be attached to a NSStatusItem on macOS, such that it behaves similarly to NSPopover, but without the popover animations and pointy bit. The code was extracted from my app AirBuddy.
Creating the controller is easy, it needs a status item to be its "target", and a view controller for its contents:
windowController = StatusBarMenuWindowController(
statusItem: // your status item,
contentViewController: // any view controller
)Important: the contentViewController must have its preferredContentSize set, the window will automatically resize itself based on that (including if it changes while visible).
To present the window attached to the status item:
windowController.showWindow(sender)If the status item's underlying window can't be found, the window will be positioned centered on screen as a fallback.
The implementation of StatusBarMenuWindowController also does a few things to make it behave more like system items like Control Center on macOS 11+, such as posting menu tracking notifications which cause the Menu Bar to stay expanded while it's visible on top of a full screen application.