Kotlin AppKit usage example (MacOS)

main.kt

import platform.AppKit.*
import platform.Foundation.NSMakeRect
import platform.Foundation.NSNotification
import platform.Foundation.NSRect
import platform.darwin.NSObject

fun main() {
    val app = NSApplication.sharedApplication()
    app.delegate = MyAppDelegate()
    app.setActivationPolicy(NSApplicationActivationPolicy.NSApplicationActivationPolicyRegular)
    app.activateIgnoringOtherApps(true)
    app.run()
}

class MyAppDelegate(): NSObject(), NSApplicationDelegateProtocol {
    private val window: NSWindow

    init {
        val rect = NSMakeRect(0.0, 0.0, 600.0, 400.0)
        window = NSWindow(
            contentRect = rect,
            styleMask = NSWindowStyleMaskClosable,
            backing = NSBackingStoreBuffered,
            defer = false
        )
        window.title = "Window"
        window.movableByWindowBackground = true
    }

    override fun applicationWillFinishLaunching(notification: NSNotification) {
        window.makeKeyAndOrderFront(null)
    }
}