/// <summary>
        /// Activates the loading screen.
        /// </summary>
        public static void Load(ScreenManager screenManager,
            EventHandler<EventArgs> loadNextScreen,
            bool loadingIsSlow)
        {
            // Tell all the current screens to transition off.
            foreach (GameScreen screen in screenManager.GetScreens())
                screen.ExitScreen();

            // Create and activate the loading screen.
            LoadingScreen loadingScreen = new LoadingScreen();

            loadingScreen.loadingIsSlow = loadingIsSlow;
            loadingScreen.loadNextScreen = loadNextScreen;

            screenManager.AddScreen(loadingScreen);
        }
        /// <summary>
        /// Activates the loading screen.
        /// </summary>
        public static void Load(ScreenManager screenManager,
                                EventHandler <EventArgs> loadNextScreen,
                                bool loadingIsSlow)
        {
            // Tell all the current screens to transition off.
            foreach (GameScreen screen in screenManager.GetScreens())
            {
                screen.ExitScreen();
            }

            // Create and activate the loading screen.
            LoadingScreen loadingScreen = new LoadingScreen();

            loadingScreen.loadingIsSlow  = loadingIsSlow;
            loadingScreen.loadNextScreen = loadNextScreen;

            screenManager.AddScreen(loadingScreen);
        }
        /// <summary>
        /// Draws the loading screen.
        /// </summary>
        public override void Draw(GameTime gameTime)
        {
            // If we are the only active screen, that means all the previous screens
            // must have finished transitioning off. We check for this in the Draw
            // method, rather than in Update, because it isn't enough just for the
            // screens to be gone: in order for the transition to look good we must
            // have actually drawn a frame without them before we perform the load.
            if ((ScreenState == ScreenState.Active) &&
                (ScreenManager.GetScreens().Length == 1))
            {
                otherScreensAreGone = true;
            }

            // The gameplay screen takes a while to load, so we display a loading
            // message while that is going on, but the menus load very quickly, and
            // it would look silly if we flashed this up for just a fraction of a
            // second while returning from the game to the menus. This parameter
            // tells us how long the loading is going to take, so we know whether
            // to bother drawing the message.
            if (loadingIsSlow)
            {
                const string message = "Loading...";

                // Center the text in the viewport.
                Viewport viewport     = ScreenManager.GraphicsDevice.Viewport;
                Vector2  viewportSize = new Vector2(viewport.Width, viewport.Height);
                Vector2  textSize     = ScreenManager.Font.MeasureString(message);
                Vector2  textPosition = (viewportSize - textSize) / 2;

                Color color = new Color(255, 255, 255, TransitionAlpha);

                // Draw the text.
                ScreenManager.SpriteBatch.Begin();

                ScreenManager.SpriteBatch.DrawString(ScreenManager.Font, message,
                                                     textPosition, color);

                ScreenManager.SpriteBatch.End();
            }
        }