//
// Timer tick. Updates scrolling of the TreeView
//
private void timer_Tick(object sender, EventArgs e)
{
// get node at mouse position
Point pt = PointToClient(MousePosition);
TreeNode node = GetNodeAt(pt);
if (node == null)
{
return;
}
// if mouse is near to the top, scroll up
if (pt.Y < 30)
{
// set actual node to the upper one
if (node.PrevVisibleNode != null)
{
node = node.PrevVisibleNode;
// hide drag image
DragHelper.ImageList_DragShowNolock(false);
// scroll and refresh
node.EnsureVisible();
Refresh();
// show drag image
DragHelper.ImageList_DragShowNolock(true);
}
}
// if mouse is near to the bottom, scroll down
else if (pt.Y > Size.Height - 30)
{
if (node.NextVisibleNode != null)
{
node = node.NextVisibleNode;
DragHelper.ImageList_DragShowNolock(false);
node.EnsureVisible();
Refresh();
DragHelper.ImageList_DragShowNolock(true);
}
}
}
//
// OnDragOver event handler. Updates the dragged node's ghost image's position
//
protected override void OnDragOver(DragEventArgs drgevent)
{
base.OnDragOver(drgevent);
// Cancel if no node is being dragged
if (_draggedNode == null)
{
return;
}
// Compute drag position and move image
var findForm = FindForm();
if (findForm != null)
{
Point formP = findForm.PointToClient(new Point(drgevent.X, drgevent.Y));
DragHelper.ImageList_DragMove(formP.X - Left, formP.Y - Top);
}
// Get actual drop node
TreeNode dropNode = GetNodeAt(PointToClient(new Point(drgevent.X, drgevent.Y)));
if (dropNode == null)
{
drgevent.Effect = DragDropEffects.None;
return;
}
TreeViewNodeDragEventArgs evArgs = new TreeViewNodeDragEventArgs(TreeViewNodeDragEventType.DragOver, TreeViewNodeDragEventBehavior.PlaceInside, _draggedNode, dropNode);
if (DragOperation != null)
{
DragOperation(evArgs);
// Cancel the operation if the user specified so
if (evArgs.Cancel)
{
drgevent.Effect = DragDropEffects.None;
OnDragDrop(drgevent);
return;
}
if (!evArgs.Allow)
{
return;
}
}
drgevent.Effect = DragDropEffects.Move;
// Dissalow the drag here
if (!evArgs.Allow)
{
drgevent.Effect = DragDropEffects.None;
}
// if mouse is on a new node select it
if (_tempDropNode != dropNode)
{
DragHelper.ImageList_DragShowNolock(false);
SelectedNode = dropNode;
DragHelper.ImageList_DragShowNolock(true);
_tempDropNode = dropNode;
}
// Avoid that drop node is child of drag node
TreeNode tmpNode = dropNode;
while (tmpNode.Parent != null)
{
if (tmpNode.Parent == _draggedNode)
{
drgevent.Effect = DragDropEffects.None;
}
tmpNode = tmpNode.Parent;
}
}
