/// <summary>
        /// The window changed size.
        /// </summary>
        /// <param name="sender">The sending object.</param>
        /// <param name="e">The event.</param>
        private void Window_SizeChanged_1(object sender, SizeChangedEventArgs e)
        {
            // Clear out any previous animation
            StopAnimation();
            CanvasOutput.Children.Clear();

            // Create new animation at correct size.
            _display = new UniverseDisplayCell((int)e.NewSize.Width, (int)e.NewSize.Height, null);
            _display.UniverseRunner.PhysicsRules.CopyData(_physics);
            _display.Visualize();
            _display.UniverseRunner.AutoKill = false;
            var img = new Image {
                Source = _display.Image
            };

            img.SetValue(Canvas.LeftProperty, 0.0);
            img.SetValue(Canvas.TopProperty, 0.0);
            CanvasOutput.Children.Add(img);

            // Start the thread.
            _stopRequest = false;
            _background  = new Thread(DoWork);
            _background.Start();
        }
        /// <summary>
        /// The window changed size.
        /// </summary>
        /// <param name="sender">The sending object.</param>
        /// <param name="e">The event.</param>
        private void Window_SizeChanged_1(object sender, SizeChangedEventArgs e)
        {
            // Clear out any previous animation
            StopAnimation();
            CanvasOutput.Children.Clear();

            // Create new animation at correct size.
            _display = new UniverseDisplayCell((int) e.NewSize.Width, (int) e.NewSize.Height, null);
            _display.UniverseRunner.PhysicsRules.CopyData(_physics);
            _display.Visualize();
            _display.UniverseRunner.AutoKill = false;
            var img = new Image {Source = _display.Image};
            img.SetValue(Canvas.LeftProperty, 0.0);
            img.SetValue(Canvas.TopProperty, 0.0);
            CanvasOutput.Children.Add(img);

            // Start the thread.
            _stopRequest = false;
            _background = new Thread(DoWork);
            _background.Start();
        }
 /// <summary>
 /// Update the user interface.
 /// </summary>
 private void UpdateUi()
 {
     _display.Visualize();
 }