borepin/Borepin/Borepin.macOS/AppDelegate.cs

using AppKit;
using Foundation;
using Xamarin.Forms;
using Xamarin.Forms.Platform.MacOS;

namespace Borepin.macOS
{
    [Register("AppDelegate")]
    public class AppDelegate : FormsApplicationDelegate
    {
        readonly NSWindow _Window;
        public AppDelegate()
        {
            NSWindowStyle style = NSWindowStyle.Closable | NSWindowStyle.Resizable | NSWindowStyle.Titled;

            CoreGraphics.CGRect rect = new CoreGraphics.CGRect(200, 1000, 1024, 768);
            _Window = new NSWindow(rect, style, NSBackingStore.Buffered, false)
            {
                Title = "Xamarin.Forms on Mac!", // choose your own Title here
                TitleVisibility = NSWindowTitleVisibility.Hidden
            };
        }

        public override NSWindow MainWindow
        {
            get 
            { 
                return _Window; 
            }
        }

        public override void DidFinishLaunching(NSNotification notification)
        {
            Forms.Init();
            LoadApplication(new App(new PlatformInitializer()));
            base.DidFinishLaunching(notification);
        }
    }
}