/// <summary>
/// Retrieves the drop target of a drag event.
/// </summary>
/// <param name="args">Information about the drag event.</param>
/// <returns>The drop target of a drag event.</returns>
protected override ItemsControl GetDropTarget(SW.DragEventArgs args)
{
DependencyObject originalSource = (DependencyObject)args.OriginalSource;
ItemsControl dropTarget = GetItemsControlAncestor(originalSource);
if (dropTarget != null)
{
TreeViewItem targetItemContainer = GetItemContainerAncestor(dropTarget, (DependencyObject)args.OriginalSource);
Orientation? orientation = GetOrientation(dropTarget);
if (orientation != null && targetItemContainer != null)
{
Rect treeViewItemRect = GetTreeViewItemRectExcludingChildren(targetItemContainer);
Point relativePoint = args.GetPosition(targetItemContainer);
double thirdWidth = treeViewItemRect.Width / 3.0;
double thirdHeight = treeViewItemRect.Height / 3.0;
// If dragging into center third of item then the drop target
// is the tree view item being hovered over.
if
((orientation == Orientation.Horizontal &&
relativePoint.X > thirdWidth && relativePoint.X < (treeViewItemRect.Width - thirdWidth)) ||
(orientation == Orientation.Vertical &&
relativePoint.Y > thirdHeight && relativePoint.Y < (treeViewItemRect.Height - thirdHeight)))
{
return(targetItemContainer);
}
}
}
return(base.GetDropTarget(args));
}
/// <summary>
/// Retrieves the original source of a new DragOver event. Attempts to
/// determine the original source by finding the the deepest element
/// in the tree that the mouse is over.
/// </summary>
/// <param name="args">Information about the drag event.</param>
/// <returns>The original source of a new DragOver event.</returns>
private static UIElement GetDragOverOriginalSource(SW.DragEventArgs args)
{
UIElement originalSource = args.OriginalSource as UIElement;
// Use the previous original source and go to its root.
// Note: this won't work if a popup appears on top of the
// original source but it will work if the previous original source
// is inside of a popup.
UIElement rootVisual = originalSource.GetVisualAncestors().OfType <UIElement>().LastOrDefault();
if (rootVisual != null)
{
// If the original source disappears (ex. a popup disappears),
// use the root visual.
rootVisual = Application.Current.RootVisual;
originalSource =
FunctionalProgramming.TraverseBreadthFirst(
rootVisual,
node => node.GetVisualChildren().OfType <UIElement>(),
node => new Rect(new Point(0, 0), node.GetSize()).Contains(args.GetPosition(node)))
.LastOrDefault();
}
return(originalSource);
}