// IControlOverrides
protected override void OnDrop(Windows.UI.Xaml.DragEventArgs e)
{
var args = e;
if (args.AcceptedOperation == DataPackageOperation.Move && !args.Handled)
{
if (m_draggedTreeViewNode != null && IsIndexValid(m_emptySlotIndex))
{
// Get the node at which we will insert
TreeViewNode insertAtNode = NodeAtFlatIndex(m_emptySlotIndex);
if (IsMutiSelectWithSelectedItems)
{
// Multiselect drag and drop. In the selected items, find all the selected subtrees
// and move each of those subtrees.
var selectedRootNodes = GetRootsOfSelectedSubtrees();
// Loop through in reverse order because we are inserting above the previous item to get the order correct.
for (int i = selectedRootNodes.Count - 1; i >= 0; --i)
{
MoveNodeInto(selectedRootNodes[i], insertAtNode);
}
}
else
{
MoveNodeInto(m_draggedTreeViewNode, insertAtNode);
}
UpdateDropTargetDropEffect(false, false, null);
args.Handled = true;
}
}
base.OnDrop(e);
}
protected override void OnDragEnter(Windows.UI.Xaml.DragEventArgs args)
{
if (!args.Handled)
{
UpdateDropTargetDropEffect(false, false, null);
}
base.OnDragEnter(args);
}
protected override void OnDragLeave(Windows.UI.Xaml.DragEventArgs args)
{
m_emptySlotIndex = -1;
base.OnDragLeave(args);
if (!args.Handled)
{
UpdateDropTargetDropEffect(false, true, null);
}
}
protected override void OnDragOver(Windows.UI.Xaml.DragEventArgs args)
{
if (!args.Handled)
{
args.AcceptedOperation = DataPackageOperation.None;
IInsertionPanel insertionPanel = (IInsertionPanel)ItemsPanelRoot;
// reorder is only supported with panels that implement IInsertionPanel
if (insertionPanel != null && m_draggedTreeViewNode != null && CanReorderItems)
{
int aboveIndex = -1;
int belowIndex = -1;
var itemsSource = ListViewModel;
int size = itemsSource.Count;
var point = args.GetPosition((UIElement)insertionPanel);
insertionPanel.GetInsertionIndexes(point, out aboveIndex, out belowIndex);
// a value of -1 means we're inserting at the end of the list or before the last item
if (belowIndex == -1)
{
// this allows the next part of this code to test if we're dropping before or after the last item
belowIndex = size - 1;
}
// if we have an insertion point
// a value of 0 means we're inserting at the beginning
// a value greater than size - 1 means we're inserting at the end as items are collapsing
if (belowIndex > size - 1)
{
// don't go out of bounds
// since items might be collapsing as we're dragging
m_emptySlotIndex = size - 1;
}
else if (belowIndex > 0 && m_draggedTreeViewNode != null)
{
m_emptySlotIndex = -1;
TreeViewNode tvi = m_draggedTreeViewNode;
if (ListViewModel.IndexOfNode(tvi, out var draggedIndex))
{
int indexToUse = (draggedIndex < belowIndex) ? belowIndex : (belowIndex - 1);
var item = ContainerFromIndex(indexToUse);
if (item != null)
{
var treeViewItem = (TreeViewItem)item;
var pointInsideItem = args.GetPosition(treeViewItem);
// if the point is in the top half of the item
// we need to insert before that item
if (pointInsideItem.Y < treeViewItem.ActualHeight / 2)
{
m_emptySlotIndex = belowIndex - 1;
}
else
{
m_emptySlotIndex = belowIndex;
}
}
}
}
else
{
// top of the list
m_emptySlotIndex = 0;
}
bool allowReorder = true;
if (IsFlatIndexValid(m_emptySlotIndex))
{
var insertAtNode = NodeAtFlatIndex(m_emptySlotIndex);
if (IsMultiselect)
{
// If insertAtNode is in the selected items, then we do not want to allow a dropping.
var selectedItems = ListViewModel.SelectedNodes;
for (var i = 0; i < selectedItems.Count; i++)
{
var selectedNode = selectedItems[i];
if (selectedNode == insertAtNode)
{
allowReorder = false;
break;
}
}
}
else
{
if (m_draggedTreeViewNode != null && insertAtNode != null && insertAtNode.Parent != null)
{
var insertContainer = ContainerFromNode(insertAtNode.Parent);
if (insertContainer != null)
{
allowReorder = ((TreeViewItem)insertContainer).AllowDrop;
}
}
}
}
else
{
// m_emptySlotIndex does not exist in the ViewModel - don't allow the reorder.
allowReorder = false;
}
if (allowReorder)
{
args.AcceptedOperation = DataPackageOperation.Move;
}
else
{
m_emptySlotIndex = -1;
args.AcceptedOperation = DataPackageOperation.None;
args.Handled = true;
}
}
UpdateDropTargetDropEffect(false, false, null);
}
base.OnDragOver(args);
}
// Required as OnDrop is protected and can't be accessed from outside internal void OnDropInternal(Windows.UI.Xaml.DragEventArgs e) => OnDrop(e);