/// <summary>
/// Determines the drag-and-drop operation which is beeing performed, which can be either None, Move or Copy.
/// </summary>
/// <param name="drgevent">DragEventArgs.</param>
/// <returns>The current drag-and-drop operation.</returns>
private DragDropEffects GetDragDropEffect(DragEventArgs drgevent)
{
const int CtrlKeyPlusLeftMouseButton = 9; // KeyState.
DragDropEffects effect = DragDropEffects.None;
// Retrieve the source control of the drag-and-drop operation.
IDragDropSource src = drgevent.Data.GetData("IDragDropSource") as IDragDropSource;
if (src != null && _dragDropGroup == src.DragDropGroup)
{ // The stuff being draged is compatible.
if (src == this)
{ // Drag-and-drop happens within this control.
if (_allowReorder && !Sorted)
{
effect = DragDropEffects.Move;
}
}
else if (_isDragDropTarget)
{
// If only Copy is allowed then copy. If Copy and Move are allowed, then Move, unless the Ctrl-key is pressed.
if (src.IsDragDropCopySource && (!src.IsDragDropMoveSource || drgevent.KeyState == CtrlKeyPlusLeftMouseButton))
{
effect = DragDropEffects.Copy;
}
else if (src.IsDragDropMoveSource)
{
effect = DragDropEffects.Move;
}
}
}
return(effect);
}
} // ReSharper restore UnusedMember.Global
private static void SourceChanged(object sender, DependencyPropertyChangedEventArgs e)
{
DependencyObject Element = sender as DependencyObject;
IDragDropSource NewSource = e.NewValue as IDragDropSource;
IDragDropSource CurrentSource = e.OldValue as IDragDropSource;
if (Element is UIElement || Element is ContentElement)
{
if (CurrentSource != null)
{
DragDropSourceAdapter Adapter;
DragDrop.dragDropSources.TryGetValue(Element, out Adapter).DbC_Assure(isSuccess => isSuccess);
DragDrop.dragDropSources.Remove(Element);
Adapter?.Dispose();
}
if (NewSource != null)
{
DragDropSourceAdapter Adapter = DragDropSourceAdapter.Create(NewSource, Element);
DragDrop.dragDropSources.Add(Element, Adapter);
}
}
else
{
throw new InvalidOperationException("Drag and Drop source can only be registered on UIElements and ContentElements");
}
}
private DragDropSourceAdapter(IDragDropSource sourceHandler, DependencyObject source)
{
this.sourceHandler = sourceHandler;
this.source = source;
this.dragSourceHandler = DragDrop.GetDragDropUISourceHandler(source.GetType()).Create(source, this);
System.Windows.DragDrop.AddGiveFeedbackHandler(this.source, DragDropSourceAdapter.GiveFeedback);
System.Windows.DragDrop.AddQueryContinueDragHandler(this.source, DragDropSourceAdapter.QueryContinueDrag);
}
static bool TryGetAsDragDropSource <T>(
object obj,
[MaybeNullWhen(false)] out IDragDropSource <T> source)
{
if (obj is ISourceList <T> sourceList)
{
source = new SourceListDragDropSource <T>(sourceList);
return(true);
}
if (obj is ISourceListUiFunnel <T> funnel)
{
source = new SourceListDragDropSource <T>(funnel.SourceList);
return(true);
}
if (obj is IDerivativeSelectedCollection <T> derivative)
{
if (derivative.OriginalList == null)
{
source = default;
return(false);
}
else
{
source = new ListDragDropSource <T>(derivative.OriginalList);
return(true);
}
}
if (obj is IList <T> l)
{
source = new ListDragDropSource <T>(l);
return(true);
}
source = default;
return(false);
}
protected override void OnDragDrop(DragEventArgs drgevent)
{
base.OnDragDrop(drgevent);
_visualCue.Clear();
// Retrieve the drag item data.
// Conditions have been testet in OnDragEnter and OnDragOver, so everything should be ok here.
IDragDropSource src = drgevent.Data.GetData("IDragDropSource") as IDragDropSource;
object[] srcItems = src.GetSelectedItems();
// If the list box is sorted, we don't know where the items will be inserted
// and we will have troubles selecting the inserted items. So let's disable sorting here.
bool sortedSave = Sorted;
Sorted = false;
// Insert at the currently hovered row.
int row = DropIndex(drgevent.Y);
int insertPoint = row;
if (row >= Items.Count)
{ // Append items to the end.
Items.AddRange(srcItems);
}
else
{ // Insert items before row.
foreach (object item in srcItems)
{
Items.Insert(row++, item);
}
}
// Remove all the selected items from the source, if moving.
DropOperation operation; // Remembers the operation for the event we'll raise.
if (drgevent.Effect == DragDropEffects.Move)
{
int adjustedInsertPoint = insertPoint;
src.RemoveSelectedItems(ref adjustedInsertPoint);
if (src == this)
{ // Items are being reordered.
insertPoint = adjustedInsertPoint;
operation = DropOperation.Reorder;
}
else
{
operation = DropOperation.MoveToHere;
}
}
else
{
operation = DropOperation.CopyToHere;
}
// Adjust the selected items in the target.
ClearSelected();
if (SelectionMode == SelectionMode.One)
{ // Select the first item inserted.
SelectedIndex = insertPoint;
}
else if (SelectionMode != SelectionMode.None)
{ // Select the inserted items.
for (int i = insertPoint; i < insertPoint + srcItems.Length; i++)
{
SetSelected(i, true);
}
}
// Now that we've selected the inserted items, restore the "Sorted" property.
Sorted = sortedSave;
// Notify the target (this control).
DroppedEventArgs e = new DroppedEventArgs
{
Operation = operation,
Source = src,
Target = this,
DroppedItems = srcItems
};
OnDropped(e);
// Notify the source (the other control).
if (operation != DropOperation.Reorder)
{
e = new DroppedEventArgs
{
Operation = operation == DropOperation.MoveToHere ? DropOperation.MoveFromHere : DropOperation.CopyFromHere,
Source = src,
Target = this,
DroppedItems = srcItems
};
src.OnDropped(e);
}
ClearSelected();
}
/// <summary>
/// Registers a IDragDropSource to the manager
/// </summary>
/// <param name="dragDropSource"></param>
public void RegisterDragDropSource(IDragDropSource dragDropSource)
{
if (dragDropSource == null) throw new ArgumentNullException("dragDropSource");
_sources.Add(dragDropSource);
RegisterDraggable(dragDropSource);
}
/// <summary>
/// Generates drop targets when a drag operation is about to begin
/// </summary>
/// <param name="source"></param>
protected void GenerateDropTargets(IDragDropSource source)
{
if (RootPanel.Children.Contains(_dropTargetLayout))
RemoveDropTargets();
_currentDragDropData = source.DragDropData;
//source cannot be its own target during drag, so filter it out of the iteration, if exists
//var dzs = _targets
// .Where(o => !(source.Equals(o)));
//.OrderBy(o => o.ZOrder)
//.SelectMany(o => o.GetDropZones(source.DragDropData));
//NOTE: Using nested foreach instead of .SelectMany (commented out above)
//NOTE: because .SelectMany seems to be making duplicate calls to o.GetDropZones(..)
_targets
.Where(o => !(source.Equals(o)))
.ToObservable()
.Subscribe(ddTarget =>
{
// ReSharper disable ConvertToLambdaExpression
ddTarget.GetDropZones(source.DragDropData)
.ToObservable()
.Subscribe(dropZone =>
{
#if DEBUG
//color up the hotspots during debug for visual reference
if (ShowDropTargets)
{
var c = (byte)(200);
((Grid)dropZone.HotSpot).Background = new SolidColorBrush(Color.FromArgb(150, c, c, c));
}
#endif
//Canvas.SetZIndex(dz.DropZoneUI, dz.Source.ZOrder);
dropZone.MouseLeftButtonUp += DropZoneMouseLeftButtonUp;
_dropTargetLayout.Children.Add(dropZone.DropZoneUI);
});
// ReSharper restore ConvertToLambdaExpression
});
RootPanel.Children.Add(_dropTargetLayout);
}
/// <summary>
/// Unregisters a IDragDropSource from the manager
/// </summary>
/// <param name="dragDropSource"></param>
public void UnRegisterDragDropSource(IDragDropSource dragDropSource)
{
if (dragDropSource == null) throw new ArgumentNullException("dragDropSource");
if (_sources.Contains(dragDropSource))
{
_sources.Remove(dragDropSource);
UnRegisterDraggable(dragDropSource);
}
}
public static DragDropSourceAdapter Create(IDragDropSource dragDropSource, DependencyObject dependencyObject)
{
return(new DragDropSourceAdapter(dragDropSource, dependencyObject));
}
// ReSharper disable UnusedMember.Global
///<summary>
/// Registers a drag and drop source handler for a given UI element
///</summary>
public static void SetSource(DependencyObject element, IDragDropSource source)
{
element.SetValue(DragDrop.SourceProperty, source);
}
