class Menu extends EditorWindow {
    @MenuItem("TestContextMenu/Open Window")
    static function Init () {
        var window = GetWindow (MyWindow);
        window.position = Rect (50, 50, 250, 60);
        window.Show ();
    }

    function Callback (obj:Object) {
        Debug.Log ("Selected: " + obj);
    }

        function OnGUI() {
            var evt : Event = Event.current;
            var contextRect : Rect = new Rect (10, 10, 100, 100);

            if (evt.type == EventType.ContextClick)
            {
                var mousePos : Vector2 = evt.mousePosition;
                if (contextRect.Contains (mousePos))
                {
                    // Now create the menu, add items and show it
                    var menu : GenericMenu = new GenericMenu ();
                    menu.AddItem (new GUIContent ("MenuItem1"), false, Callback, "item 1");
                    menu.AddItem (new GUIContent ("MenuItem2"), false, Callback, "item 2");
                    menu.AddSeparator ("");
                    menu.AddItem (new GUIContent ("SubMenu/MenuItem3"), false, Callback, "item 3");
                    menu.ShowAsContext ();

                    evt.Use();
                }
            }
        }
    }
}