/// <summary>
        /// The constructor is private: loading screens should
        /// be activated via the static Load method instead.
        /// </summary>
        private LoadingScreen(ScreenManager screenManager, bool loadingIsSlow,
            GameScreen[] screensToLoad)
        {
            this.loadingIsSlow = loadingIsSlow;
            this.screensToLoad = screensToLoad;

            TransitionOnTime = TimeSpan.FromSeconds(0.5);
        }
        /// <summary>
        /// Removes a screen from the screen manager. You should normally
        /// use GameScreen.ExitScreen instead of calling this directly, so
        /// the screen can gradually transition off rather than just being
        /// instantly removed.
        /// </summary>
        public void RemoveScreen(GameScreen screen)
        {
            // If we have a graphics device, tell the screen to unload content.
            if (isInitialized)
            {
                screen.Unload();
            }

            screens.Remove(screen);
            tempScreensList.Remove(screen);

            // if there is a screen still in the manager, update TouchPanel
            // to respond to gestures that screen is interested in.
            if (screens.Count > 0)
            {
                TouchPanel.EnabledGestures = screens[screens.Count - 1].EnabledGestures;
            }
        }
        /// <summary>
        /// Adds a new screen to the screen manager.
        /// </summary>
        public void AddScreen(GameScreen screen, PlayerIndex? controllingPlayer)
        {
            screen.ControllingPlayer = controllingPlayer;
            screen.ScreenManager = this;
            screen.IsExiting = false;

            // If we have a graphics device, tell the screen to load content.
            if (isInitialized)
            {
                screen.Activate(false);
            }

            screens.Add(screen);

            // update the TouchPanel to respond to gestures this screen is interested in
            TouchPanel.EnabledGestures = screen.EnabledGestures;
        }
        /// <summary>
        /// Draws the button
        /// </summary>
        /// <param name="screen">The screen drawing the button</param>
        public void Draw(GameScreen screen)
        {
            // Grab some common items from the ScreenManager
            SpriteBatch spriteBatch = screen.ScreenManager.SpriteBatch;
            SpriteFont font = screen.ScreenManager.Font;
            Texture2D blank = screen.ScreenManager.BlankTexture;

            // Compute the button's rectangle
            Rectangle r = new Rectangle(
                (int)Position.X,
                (int)Position.Y,
                (int)Size.X,
                (int)Size.Y);

            // Fill the button
            spriteBatch.Draw(blank, r, FillColor * Alpha);

            // Draw the border
            spriteBatch.Draw(
                blank,
                new Rectangle(r.Left, r.Top, r.Width, BorderThickness),
                BorderColor * Alpha);
            spriteBatch.Draw(
                blank,
                new Rectangle(r.Left, r.Top, BorderThickness, r.Height),
                BorderColor * Alpha);
            spriteBatch.Draw(
                blank,
                new Rectangle(r.Right - BorderThickness, r.Top, BorderThickness, r.Height),
                BorderColor * Alpha);
            spriteBatch.Draw(
                blank,
                new Rectangle(r.Left, r.Bottom - BorderThickness, r.Width, BorderThickness),
                BorderColor * Alpha);

            // Draw the text centered in the button
            Vector2 textSize = font.MeasureString(Text);
            Vector2 textPosition = new Vector2(r.Center.X, r.Center.Y) - textSize / 2f;
            textPosition.X = (int)textPosition.X;
            textPosition.Y = (int)textPosition.Y;
            spriteBatch.DrawString(font, Text, textPosition, TextColor * Alpha);
        }