private static DropItemLocationAdorner GetAdorner(IDragDropFeedback feedback, FrameworkElement draggedOverElement, bool createIfNeeded)
{
var dragDropFeedback = (DragDropFeedback)feedback;
DropItemLocationAdorner adorner = (dragDropFeedback != null) ? dragDropFeedback.Adorner : null;
if (adorner == null)
{
var adornedElement = GetRootItemsControl(draggedOverElement);
if ((adornedElement != null) && DragDropRearrangeBehavior.GetAllowsDragDropRearrange(adornedElement))
{
if ((adorner == null) && createIfNeeded)
{
adorner = new DropItemLocationAdorner(adornedElement, draggedOverElement);
dragDropFeedback.Adorner = adorner;
}
}
}
else if ((draggedOverElement != adorner.AdornedItemsControl) && (draggedOverElement.GetParent <ItemsControl>(i => i == adorner.AdornedItemsControl) == null))
{
if (dragDropFeedback != null)
{
dragDropFeedback.DropLocation = DropOnItemLocation.None;
}
}
return(adorner);
}
/// <summary>
/// Update the adorner's location, etc.
/// </summary>
/// <param name="draggedOverElement">The item being dragged over.</param>
/// <param name="dragDropFeedback">Feedback interface.</param>
/// <param name="exitDragDrop">If <c>true</c>, we're doing a drag-drop exit.</param>
public static void Update(FrameworkElement draggedOverElement, IDragDropFeedback dragDropFeedback, bool exitDragDrop)
{
var ending = (dragDropFeedback == null) || (dragDropFeedback.DropLocation == DropOnItemLocation.None);
var adorner = GetAdorner(dragDropFeedback, draggedOverElement, !ending); // may modify the feedback
ending = (dragDropFeedback == null) || (dragDropFeedback.DropLocation == DropOnItemLocation.None);
if (ending || exitDragDrop)
{
if (adorner != null)
{
adorner.Remove(dragDropFeedback, exitDragDrop);
}
}
else
{
if ((adorner != null) && (draggedOverElement != adorner.AdornedElement))
{
if (adorner.Layer == null)
{
adorner.Layer = AdornerLayer.GetAdornerLayer(adorner.AdornedElement);
adorner.Layer.Add(adorner);
}
// fix up size / position
adorner.SuspendUpdates = true;
adorner.DragOverElement = draggedOverElement;
adorner.DropLocation = dragDropFeedback.DropLocation;
adorner.AllowsChildren = dragDropFeedback.AllowsChildren;
adorner.SuspendUpdates = false;
}
}
}
private void Remove(IDragDropFeedback feedback, bool exitDragDrop)
{
if (Layer != null)
{
Layer.Remove(this);
Layer = null;
if (exitDragDrop)
{
((DragDropFeedback)feedback).Adorner = null;
}
}
SuspendUpdates = true;
DragOverElement = null;
DropLocation = DropOnItemLocation.None;
SomethingChanged = false;
AllowsChildren = false;
}
private static void HandleDragOver(object sender, DragEventArgs args)
{
var visual = sender as FrameworkElement;
IDragDropFeedback dragDropFeedback = null;
if (args.Data.GetDataPresent(DragDropHelpers.DragDropFeedbackDataFormat))
{
dragDropFeedback = args.Data.GetData(DragDropHelpers.DragDropFeedbackDataFormat) as IDragDropFeedback;
}
else
{
var itemsControl = visual as System.Windows.Controls.ItemsControl;
var allowsRearrange = (itemsControl != null) && DragDropRearrangeBehavior.GetAllowsDragDropRearrange(itemsControl);
if (allowsRearrange)
{
dragDropFeedback = new DragDropFeedback();
args.Data.SetData(DragDropHelpers.DragDropFeedbackDataFormat, dragDropFeedback);
}
}
if (dragDropFeedback != null)
{
var height = visual.ActualHeight;
var location = args.GetPosition(visual);
var dropLocation = GetDropLocation(visual, location);
dragDropFeedback.DropLocation = dropLocation;
}
GetDragOverCommand(visual).Execute(args);
if (dragDropFeedback != null)
{
if (args.Effects == DragDropEffects.None)
{
dragDropFeedback.DropLocation = DropOnItemLocation.None;
}
DropItemLocationAdorner.Update(visual, dragDropFeedback, false);
}
args.Handled = true;
}
