Wrap Panel Virtualization

using System.ComponentModel.Composition;
using System.Windows;
using System.Windows.Controls;
using MediaAssistant.Controls.WaitScreen;
using MefBasic;
using MefBasic.Threading;
using MediaAssistant.DAL;

namespace MediaAssistant.Controls.MovieThumbnails
{
    [Export]
    public partial class MovieThumbnailsView : IView
    {
        public MovieThumbnailsView()
        {
            InitializeComponent();
        }

        private void HandleScrollChanged(object sender, ScrollChangedEventArgs e)
        {
            ShowVisibleItems(sender);
        }

        private void ShowVisibleItems(object sender)
        {
            var scrollViewer = (FrameworkElement) sender;
            var visibleAreaEntered = false;
            var visibleAreaLeft = false;
            var invisibleItemDisplayed = 0;
            foreach (Movie item in thumbnailListBox.Items)
            {
                if (item.IsVisible) continue;
                var listBoxItem = (FrameworkElement) thumbnailListBox.ItemContainerGenerator.ContainerFromItem(item);
                if (visibleAreaLeft==false && IsFullyOrPartiallyVisible(listBoxItem, scrollViewer))
                {
                    visibleAreaEntered = true;
                }
                else if (visibleAreaEntered)
                {
                    visibleAreaLeft = true;
                }
                if(visibleAreaEntered)
                {
                    if(visibleAreaLeft && ++invisibleItemDisplayed>10)
                        break;
                    var job = new Job(MakeVisible);
                    job.Store.Add(item);
                    job.Start();
                }
            }
        }

        private static void MakeVisible(Job obj)
        {
            obj.Store.GetObject<Movie>().IsVisible = true;
        }

        protected bool IsFullyOrPartiallyVisible(FrameworkElement child, FrameworkElement scrollViewer)
        {
            var childTransform = child.TransformToAncestor(scrollViewer);
            var childRectangle = childTransform.TransformBounds(new Rect(new Point(0, 0), child.RenderSize));
            var ownerRectangle = new Rect(new Point(0, 0), scrollViewer.RenderSize);
            return ownerRectangle.IntersectsWith(childRectangle);
        }

    }
}