MacOS-改变默认Window的尺寸

更改MacOS工程的窗口尺寸和位置.

在applicationDidFinishLaunching 方法中，窗口还未激活，mainWindow 并没有值

func applicationDidFinishLaunching(_ aNotification: Notification) {
    // Insert code here to initialize your application
    modifyWindowSize()
}

// modify the window default size
func modifyWindowSize() {
    
    guard let screen = NSScreen.main else {
        print("screen is unavailable")
        return
    }
    
    /**
        NSApplication.shared.mainWindow 只有在窗口被激活时才会返回正确的值。如果窗口还没有成为主窗口，mainWindow 的值将为 nil。
        */
//        guard let mainWindow = NSApplication.shared.mainWindow else {
//            print("mainWindow is unavailable")
//            return
//        }
    
    guard let mainWindow = NSApp.windows.first else {
        print("mainWindow is unavailable")
        return
    }
    
    let screenFrame = screen.visibleFrame
    
    let width = 800.0
    let height = 600.0
    
    let x = NSMidX(screenFrame) - width * 0.5
    let y = NSMidY(screenFrame) - height * 0.5

    // 创建窗口尺寸相对屏幕中心的位置
    
    let frame = NSMakeRect(x, y, width, height)

    mainWindow.setFrame(frame, display: true)

}