//
// OnDragLeave event handler. Updates the dragged node's ghost image's position.
//
protected override void OnDragLeave(EventArgs e)
{
base.OnDragLeave(e);
DragHelper.ImageList_DragLeave(Handle);
// Disable timer for scrolling dragged item
_timer.Enabled = false;
}
//
// OnDragEnter event handler. Updates the dragged node's ghost image's position.
//
protected override void OnDragEnter(DragEventArgs drgevent)
{
base.OnDragEnter(drgevent);
DragHelper.ImageList_DragEnter(Handle, drgevent.X - Left, drgevent.Y - Top);
// Enable timer for scrolling dragged item
_timer.Enabled = true;
}
//
// 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);
}
}
}
//
// OnDragDrop event handler. Ends a node dragging
//
protected override void OnDragDrop(DragEventArgs drgevent)
{
base.OnDragDrop(drgevent);
// Cancel if no node is being dragged
if (_draggedNode == null)
{
return;
}
// Unlock updates
DragHelper.ImageList_DragLeave(Handle);
if (drgevent.Effect == DragDropEffects.None)
{
// Set drag node and temp drop node to null
_draggedNode = null;
_tempDropNode = null;
// Disable scroll timer
_timer.Enabled = false;
return;
}
// Get drop node
TreeNode dropNode = GetNodeAt(PointToClient(new Point(drgevent.X, drgevent.Y)));
// Launch the feedback for the drag operation
TreeViewNodeDragEventArgs evArgs = new TreeViewNodeDragEventArgs(TreeViewNodeDragEventType.DragEnd, TreeViewNodeDragEventBehavior.PlaceInside, _draggedNode, dropNode);
if (DragOperation != null)
{
DragOperation(evArgs);
// Cancel the operation if the user specified so
if (evArgs.Cancel)
{
return;
}
}
// If drop node isn't equal to drag node, add drag node as child of drop node
if (_draggedNode != dropNode)
{
// Remove drag node from parent
if (_draggedNode.Parent == null)
{
Nodes.Remove(_draggedNode);
}
else
{
_draggedNode.Parent.Nodes.Remove(_draggedNode);
}
// Place the dragged node before or after the target node depending on mouse position
if (evArgs.EventBehavior == TreeViewNodeDragEventBehavior.PlaceBeforeOrAfterAuto)
{
// Get drop node
Point mouseP = PointToClient(MousePosition);
// Figure out whether the node should be added uder or over the pointed item by checking if the mouse is under or over the middle of the item
evArgs.EventBehavior = mouseP.Y > dropNode.Bounds.Y + dropNode.Bounds.Height / 2
? TreeViewNodeDragEventBehavior.PlaceAfter
: TreeViewNodeDragEventBehavior.PlaceBefore;
}
// Place the dragged node before the target node
if (evArgs.EventBehavior == TreeViewNodeDragEventBehavior.PlaceBefore)
{
// Add drag node before drop node
if (dropNode.Parent != null)
{
dropNode.Parent.Nodes.Insert(dropNode.Index, _draggedNode);
}
else
{
Nodes.Insert(dropNode.Index, _draggedNode);
}
SelectedNode = _draggedNode;
}
// Place the dragged node after the target node
if (evArgs.EventBehavior == TreeViewNodeDragEventBehavior.PlaceAfter)
{
// Add drag node after drop node
if (dropNode.Parent != null)
{
dropNode.Parent.Nodes.Insert(dropNode.Index + 1, _draggedNode);
}
else
{
Nodes.Insert(dropNode.Index + 1, _draggedNode);
}
SelectedNode = _draggedNode;
}
// Place the dragged node inside the target node
if (evArgs.EventBehavior == TreeViewNodeDragEventBehavior.PlaceInside)
{
// Add drag node to drop node
dropNode.Nodes.Add(_draggedNode);
dropNode.ExpandAll();
}
// Launch the feedback for the drag operation
evArgs = new TreeViewNodeDragEventArgs(TreeViewNodeDragEventType.AfterDragEnd, evArgs.EventBehavior, _draggedNode, dropNode);
DragOperation?.Invoke(evArgs);
// Set drag node and temp drop node to null
_draggedNode = null;
_tempDropNode = null;
// Disable scroll timer
_timer.Enabled = false;
}
}
//
// 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;
}
}
//
// OnItemDrag event handler. Starts dragging a node
//
protected override void OnItemDrag(ItemDragEventArgs e)
{
base.OnItemDrag(e);
SelectedNode = (TreeNode)e.Item;
TreeViewNodeDragEventArgs evArgs = new TreeViewNodeDragEventArgs(TreeViewNodeDragEventType.DragStart, TreeViewNodeDragEventBehavior.PlaceInside, (TreeNode)e.Item, null);
if (DragOperation != null)
{
DragOperation(evArgs);
// Cancel the operation if the user specified so
if (evArgs.Cancel)
{
return;
}
}
// Get drag node and select it
_draggedNode = (TreeNode)e.Item;
SelectedNode = evArgs.DraggedNode;
// Reset image list used for drag image
_imageListDrag.Images.Clear();
_imageListDrag.ImageSize = new Size(_draggedNode.Bounds.Size.Width + Indent, _draggedNode.Bounds.Height);
//// Create new bitmap
// This bitmap will contain the tree node image to be dragged
Bitmap bmp = new Bitmap(_draggedNode.Bounds.Width + Indent, _draggedNode.Bounds.Height);
SolidBrush brush = new SolidBrush(ForeColor);
// Get graphics from bitmap
Graphics gfx = Graphics.FromImage(bmp);
gfx.SmoothingMode = SmoothingMode.HighQuality;
gfx.TextRenderingHint = System.Drawing.Text.TextRenderingHint.ClearTypeGridFit;
// Draw node icon into the bitmap
if (_draggedNode.ImageKey == "")
{
gfx.DrawImage(ImageList.Images[_draggedNode.ImageIndex], 0, 0);
}
else
{
if (ImageList?.Images[_draggedNode.ImageKey] != null)
{
gfx.DrawImage(ImageList.Images[_draggedNode.ImageKey], 0, 0);
}
}
// Draw node label into bitmap
gfx.DrawString(_draggedNode.Text, Font, brush, Indent, 1.0f);
gfx.Flush();
gfx.Dispose();
brush.Dispose();
// Add bitmap to imagelist
_imageListDrag.Images.Add(bmp);
// Get mouse position in client coordinates
Point p = PointToClient(MousePosition);
// Compute delta between mouse position and node bounds
int dx = p.X + Indent - _draggedNode.Bounds.Left;
int dy = p.Y - _draggedNode.Bounds.Top;
// Begin dragging image
if (DragHelper.ImageList_BeginDrag(_imageListDrag.Handle, 0, dx, dy))
{
// Begin dragging
DoDragDrop(bmp, DragDropEffects.Move);
// End dragging image
DragHelper.ImageList_EndDrag();
}
}
