/// <summary>
/// Retrieves all the logical descendents of a framework element using a
/// breadth-first search. For performance reasons this method manually
/// manages the stack instead of using recursion.
/// </summary>
/// <param name="parent">The parent framework element.</param>
/// <returns>The logical children of the framework element.</returns>
internal static IEnumerable <FrameworkElement> GetLogicalDescendents(this FrameworkElement parent)
{
Debug.Assert(parent != null, "The parent cannot be null.");
return
(FunctionalProgramming.TraverseBreadthFirst(
parent,
node => node.GetLogicalChildren(),
node => true));
}
/// <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);
}
