internal void HandleDragOver(SharpTreeViewItem item, DragEventArgs e)
{
HidePreview();
var target = GetDropTarget(item, e);
if (target != null)
{
e.Handled = true;
ShowPreview(target.Item, target.Place);
}
var sv = STVUTILS.TryGetScrollViewer(this);
double tolerance = item.NodeView.ActualHeight / 2;
double verticalPos = e.GetPosition(this).Y;
// take the difference between tolerance and position to scroll more rapidly as tolerance gap closes
if (verticalPos < tolerance)
{
sv.ScrollToVerticalOffset(sv.VerticalOffset - (tolerance - verticalPos));
}
else if (verticalPos > ActualHeight - tolerance)
{
sv.ScrollToVerticalOffset(sv.VerticalOffset + (verticalPos - ActualHeight + tolerance));
}
}
/// <summary>
/// Handles the node expanding event in the tree view.
/// This method gets called only if the node is in the visible region (a SharpTreeNodeView exists).
/// </summary>
internal void HandleExpanding(SharpTreeNode node)
{
if (doNotScrollOnExpanding)
{
return;
}
SharpTreeNode lastVisibleChild = node;
while (true)
{
SharpTreeNode tmp = lastVisibleChild.Children.LastOrDefault(c => c.IsVisible);
if (tmp != null)
{
lastVisibleChild = tmp;
}
else
{
break;
}
}
if (lastVisibleChild != node)
{
Debug.Assert(flattener != null);
if (flattener == null)
{
return;
}
// A new scrollViewer.ViewportHeight value is available at the earliest at Render prio.
// If there are many empty lines, it will equal the number of visible items (eg. 5,
// but viewport can show eg. 10).
Dispatcher.BeginInvoke(DispatcherPriority.Render, new Action(() => {
var itemsPerPage = STVUTILS.GetItemsPerPage(this, 0);
int nodeIndex = flattener.IndexOf(node);
int lastVisibleChildIndex = flattener.IndexOf(lastVisibleChild);
Debug.Assert(nodeIndex >= 0 && lastVisibleChildIndex >= 0);
if (itemsPerPage > 0 && nodeIndex >= 0 && lastVisibleChildIndex >= 0)
{
int lastIndex = Math.Min(lastVisibleChildIndex, nodeIndex + itemsPerPage - 1);
ScrollIntoView(Items[lastIndex]);
Dispatcher.BeginInvoke(DispatcherPriority.Loaded, new Action(() => ScrollIntoView(node)));
}
}));
}
}
