/// <summary>
/// Removes existing placeholders and draws a new one according to the given location.
/// </summary>
/// <param name="location">Location of the placeholder to draw</param>
/// <param name="node">Node we're over (set null if location is None)</param>
/// <param name="parent">Parent node (only relevent to leaf bottom location, set
/// null otherwise)</param>
private void SetPlaceholders(PlaceholderLocation location, TreeNode node, TreeNode parent)
{
// Clear placeholders
if (_placeholdersVisible)
{
Refresh();
}
// Set placeholder flag
_placeholdersVisible = location != PlaceholderLocation.None;
// Draw the proper one
switch (location)
{
case PlaceholderLocation.LeafTop:
DrawLeafTopPlaceholders(node);
break;
case PlaceholderLocation.LeafBottom:
DrawLeafBottomPlaceholders(node, parent);
break;
case PlaceholderLocation.FolderTop:
DrawFolderTopPlaceholders(node);
break;
case PlaceholderLocation.FolderAdd:
DrawAddToFolderPlaceholder(node);
break;
case PlaceholderLocation.FolderBottom:
DrawFolderBottomPlaceholders(node);
break;
}
}
/// <summary>
/// This method handles the <see cref="TreeView.DragOver"/> event for a <see cref="TreeViewControl"/>.
/// </summary>
/// <param name="treeView">The <see cref="TreeView"/> of the <see cref="TreeViewControl"/>.</param>
/// <param name="e">The arguments of the <see cref="TreeView.DragOver"/> event.</param>
/// <param name="getTreeNodeInfoForData">A function for obtaining the <see cref="TreeNodeInfo"/> object corresponding to a provided data object.</param>
public void HandleDragOver(FormsTreeView treeView, DragEventArgs e, Func <object, TreeNodeInfo> getTreeNodeInfoForData)
{
if (lastDragOverPoint.X == e.X && lastDragOverPoint.Y == e.Y)
{
return;
}
lastDragOverPoint = new Point(e.X, e.Y);
Point point = treeView.PointToClient(lastDragOverPoint);
TreeNode nodeOver = treeView.GetNodeAt(point);
TreeNode draggedNode = GetDraggedNodeData(e);
if (draggedNode == null || nodeOver == null || nodeOver == draggedNode || IsDropTargetChildOfDraggedNode(nodeOver, draggedNode))
{
RemovePlaceHolder(treeView);
e.Effect = DragDropEffects.None;
return;
}
ScrollIntoView(point, nodeOver, treeView);
PlaceholderLocation placeholderLocation = GetPlaceHoldersLocation(treeView, draggedNode, nodeOver, getTreeNodeInfoForData);
if (nodeDropTarget == null)
{
return;
}
TreeNodeInfo treeNodeInfo = getTreeNodeInfoForData(nodeDropTarget.Tag);
bool canDrop = treeNodeInfo.CanDrop != null && treeNodeInfo.CanDrop(draggedNode.Tag, nodeDropTarget.Tag);
e.Effect = canDrop ? DragDropEffects.Move : DragDropEffects.None;
if (placeholderLocation == PlaceholderLocation.None)
{
RemovePlaceHolder(treeView);
e.Effect = DragDropEffects.None;
return;
}
if (canDrop)
{
CreatePlaceholder(treeView, nodeOver, placeholderLocation);
}
else
{
RemovePlaceHolder(treeView);
e.Effect = DragDropEffects.None;
}
}
private void CreatePlaceholder(FormsTreeView treeView, TreeNode node, PlaceholderLocation placeHolderLocation)
{
if (lastPlaceholderNode == node && lastPlaceholderLocation == placeHolderLocation)
{
return;
}
RemovePlaceHolder(treeView);
lastPlaceholderNode = node;
lastPlaceholderLocation = placeHolderLocation;
placeHolderGraphics = treeView.CreateGraphics();
DrawPlaceHolder(node, placeHolderLocation, treeView.CreateGraphics());
}
private static void DrawPlaceHolder(TreeNode node, PlaceholderLocation location, Graphics graphics)
{
Point[] rightTriangle = MakePlaceHoldeTriangle(node, AnchorStyles.Right, location);
graphics.FillPolygon(Brushes.Black, rightTriangle);
if (location == PlaceholderLocation.Middle)
{
return;
}
Point[] leftTriangle = MakePlaceHoldeTriangle(node, AnchorStyles.Left, location);
graphics.FillPolygon(Brushes.Black, leftTriangle);
int yLine = location == PlaceholderLocation.Top
? node.Bounds.Top
: node.Bounds.Bottom;
graphics.DrawLine(new Pen(Color.Black, 1), new Point(GetImageLeft(node), yLine), new Point(node.Bounds.Right, yLine));
}
private static Point[] MakePlaceHoldeTriangle(TreeNode node, AnchorStyles anchor, PlaceholderLocation location)
{
const int placeHolderWidth = 4;
const int placeHolderHeight = 8;
int xPos, yPos;
Rectangle bounds = node.Bounds;
switch (anchor)
{
case AnchorStyles.Left:
xPos = GetImageLeft(node) - placeHolderWidth;
break;
case AnchorStyles.Right:
xPos = bounds.Right;
break;
default:
throw new NotSupportedException();
}
switch (location)
{
case PlaceholderLocation.Top:
yPos = bounds.Top;
break;
case PlaceholderLocation.Bottom:
yPos = bounds.Bottom;
break;
case PlaceholderLocation.Middle:
yPos = bounds.Top + bounds.Height / 2;
break;
default:
throw new NotSupportedException();
}
return(CreateTrianglePoints(new Rectangle(xPos, yPos - placeHolderWidth, placeHolderWidth, placeHolderHeight), anchor));
}