internal bool IsOnCurrentPage(ListBoxItem item)
{
var itemsHostRect = Rect.Empty;
var listBoxItemRect = Rect.Empty;
if (_visual == null)
{
ItemsControlHelper ich = new ItemsControlHelper(ListBox);
ScrollContentPresenter scp = ich.ScrollHost == null ? null : ich.ScrollHost.GetVisualDescendants().OfType<ScrollContentPresenter>().FirstOrDefault();
_visual = (ich.ScrollHost == null) ? null : ((scp == null) ? ((FrameworkElement)ich.ScrollHost) : ((FrameworkElement)scp));
}
if (_visual == null)
return true;
itemsHostRect = new Rect(0.0, 0.0, _visual.ActualWidth, _visual.ActualHeight);
//ListBoxItem item = ListBox.ItemContainerGenerator.ContainerFromIndex(index) as ListBoxItem;
if (item == null)
{
listBoxItemRect = Rect.Empty;
return false;
}
GeneralTransform transform = item.TransformToVisual(_visual);
listBoxItemRect = new Rect(transform.Transform(new Point()), transform.Transform(new Point(item.ActualWidth, item.ActualHeight)));
if (!this.IsVerticalOrientation())
{
return ((itemsHostRect.Left <= listBoxItemRect.Left) && (listBoxItemRect.Right <= itemsHostRect.Right));
}
return ((listBoxItemRect.Bottom + 100 >= itemsHostRect.Top) && (listBoxItemRect.Top - 100 <= itemsHostRect.Bottom));
//return ((itemsHostRect.Top <= listBoxItemRect.Bottom) && (listBoxItemRect.Top <= itemsHostRect.Bottom));
}
/// <summary>
/// Indicate whether the specified item is currently visible.
/// </summary>
/// <param name="item">The item.</param>
/// <param name="itemsHostRect">Rect for the item host element.</param>
/// <param name="listBoxItemRect">Rect for the ListBoxItem element.</param>
/// <returns>True if the item is visible; false otherwise.</returns>
/// <remarks>Similar to WPF's corresponding ItemsControl method.</remarks>
private bool IsOnCurrentPage(object item, out Rect itemsHostRect, out Rect listBoxItemRect)
{
// Get Rect for item host element
DependencyObject ItemsHost = VisualTreeHelper.GetChild(this, 0);
ItemsHost = VisualTreeHelper.GetChild(ItemsHost, 0);
FrameworkElement itemsHost =
(null != TemplateScrollViewer) ?
((null != TemplateScrollViewer.ElementScrollContentPresenter) ? TemplateScrollViewer.ElementScrollContentPresenter as FrameworkElement : TemplateScrollViewer as FrameworkElement) :
ItemsHost as FrameworkElement;
if (itemsHost == null)
{
itemsHostRect = Rect.Empty;
listBoxItemRect = Rect.Empty;
return(false);
}
itemsHostRect = new Rect(new Point(), new Point(itemsHost.RenderSize.Width, itemsHost.RenderSize.Height));
ListBoxItem listBoxItem = (ListBoxItem)ItemContainerGenerator.ContainerFromItem(item);
if (listBoxItem == null)
{
listBoxItemRect = Rect.Empty;
return(false);
}
listBoxItemRect = new Rect(new Point(), listBoxItem.RenderSize);
// Adjust Rect to account for padding
Control itemsHostControl = itemsHost as Control;
if (null != itemsHostControl)
{
Thickness padding = itemsHostControl.Padding;
itemsHostRect = new Rect(
itemsHostRect.Left + padding.Left,
itemsHostRect.Top + padding.Top,
itemsHostRect.Width - padding.Left - padding.Right,
itemsHostRect.Height - padding.Top - padding.Bottom);
}
// Get relative Rect for ListBoxItem
GeneralTransform generalTransform = listBoxItem.TransformToVisual(itemsHost);
if (generalTransform != null)
{
listBoxItemRect = new Rect(generalTransform.Transform(new Point()), generalTransform.Transform(new Point(listBoxItem.RenderSize.Width, listBoxItem.RenderSize.Height)));
}
// Return result
return(IsVerticalOrientation() ?
(itemsHostRect.Top <= listBoxItemRect.Top) && (listBoxItemRect.Bottom <= itemsHostRect.Bottom) :
(itemsHostRect.Left <= listBoxItemRect.Left) && (listBoxItemRect.Right <= itemsHostRect.Right));
}