gui cocoa: better main window handling
gui cocoa: better main window handling

albertz/music-player,kingsj/music-player,kingsj/music-player,kingsj/music-player,kingsj/music-player,albertz/music-player,albertz/music-player,albertz/music-player,kingsj/music-player,albertz/music-player,albertz/music-player