Artemis.Styles.DropTargetAdorners.DropTargetMetroInsertionAdorner.OnRender C# (CSharp) Метод

        protected override void OnRender(DrawingContext drawingContext)
        {
            var itemsControl = DropInfo.VisualTarget as ItemsControl;

            if (itemsControl != null)
            {
                // Get the position of the item at the insertion index. If the insertion point is
                // to be after the last item, then get the position of the last item and add an 
                // offset later to draw it at the end of the list.
                ItemsControl itemParent;

                if (DropInfo.VisualTargetItem != null)
                {
                    itemParent = ItemsControl.ItemsControlFromItemContainer(DropInfo.VisualTargetItem);
                }
                else
                {
                    itemParent = itemsControl;
                }

                var index = Math.Min(DropInfo.InsertIndex, itemParent.Items.Count - 1);

                var lastItemInGroup = false;
                var targetGroup = DropInfo.TargetGroup;
                if (targetGroup != null && targetGroup.IsBottomLevel &&
                    DropInfo.InsertPosition.HasFlag(RelativeInsertPosition.AfterTargetItem))
                {
                    var indexOf = targetGroup.Items.IndexOf(DropInfo.TargetItem);
                    lastItemInGroup = indexOf == targetGroup.ItemCount - 1;
                    if (lastItemInGroup && DropInfo.InsertIndex != itemParent.Items.Count)
                    {
                        index--;
                    }
                }

                var itemContainer = (UIElement) itemParent.ItemContainerGenerator.ContainerFromIndex(index);

                if (itemContainer != null)
                {
                    var itemRect = new Rect(itemContainer.TranslatePoint(new Point(), AdornedElement),
                        itemContainer.RenderSize);
                    Point point1, point2;
                    double rotation = 0;

                    if (DropInfo.VisualTargetOrientation == Orientation.Vertical)
                    {
                        if (DropInfo.InsertIndex == itemParent.Items.Count || lastItemInGroup)
                        {
                            itemRect.Y += itemContainer.RenderSize.Height;
                        }

                        point1 = new Point(itemRect.X, itemRect.Y);
                        point2 = new Point(itemRect.Right, itemRect.Y);
                    }
                    else
                    {
                        var itemRectX = itemRect.X;

                        if (DropInfo.VisualTargetFlowDirection == FlowDirection.LeftToRight &&
                            DropInfo.InsertIndex == itemParent.Items.Count)
                        {
                            itemRectX += itemContainer.RenderSize.Width;
                        }
                        else if (DropInfo.VisualTargetFlowDirection == FlowDirection.RightToLeft &&
                                 DropInfo.InsertIndex != itemParent.Items.Count)
                        {
                            itemRectX += itemContainer.RenderSize.Width;
                        }

                        point1 = new Point(itemRectX, itemRect.Y);
                        point2 = new Point(itemRectX, itemRect.Bottom);
                        rotation = 90;
                    }

                    drawingContext.DrawLine(m_Pen, point1, point2);
                    DrawTriangle(drawingContext, point1, rotation);
                    DrawTriangle(drawingContext, point2, 180 + rotation);
                }
            }
        }