Method OnDrop

Source/FlowEditor/Private/Graph/Widgets/SFlowGraphNode.cpp:1153–1230

}

FReply SFlowGraphNode::OnDrop(const FGeometry& MyGeometry, const FDragDropEvent& DragDropEvent)
{
	SetDragMarker(false);

	const TSharedPtr<FDragFlowGraphNode> DragNodeOp = DragDropEvent.GetOperationAs<FDragFlowGraphNode>();
	if (DragNodeOp.IsValid())
	{
		if (!DragNodeOp->IsValidOperation())
		{
			return FReply::Handled();
		}

		const float DragTime = static_cast<float>(FPlatformTime::Seconds() - DragNodeOp->StartTime);
		if (DragTime < 0.5f)
		{
			return FReply::Handled();
		}

		if (FlowGraphNode == nullptr)
		{
			return FReply::Unhandled();
		}

		const FScopedTransaction Transaction(LOCTEXT("GraphEd_DragDropNode", "Drag&Drop Node"));

		UFlowGraphNode* DropTargetNode = DragNodeOp->GetDropTargetNode();
		check(DropTargetNode);

		bool bReorderOperation = true;
		const TArray< TSharedRef<SGraphNode> >& DraggedNodes = DragNodeOp->GetNodes();
		RemoveDraggedSubNodes(DraggedNodes, bReorderOperation);

		const bool bShouldDropAsSubNodesOfDropTargetNode = bReorderOperation || ShouldDropDraggedNodesAsSubNodes(DraggedNodes, DropTargetNode);

		// Set up the DropTarget pointers based on the type of drop we've decided to do:
		UFlowGraphNode* DropTargetParentNode;
		if (bShouldDropAsSubNodesOfDropTargetNode)
		{
			DropTargetParentNode = DropTargetNode;
			DropTargetNode = nullptr;
		}
		else
		{
			DropTargetParentNode = DropTargetNode->GetParentNode();
		}

		check(DropTargetParentNode);

		const int32 InsertIndex = DropTargetParentNode->FindSubNodeDropIndex(DropTargetNode);

		for (int32 Idx = 0; Idx < DraggedNodes.Num(); Idx++)
		{
			UFlowGraphNode* DraggedTestNode = Cast<UFlowGraphNode>(DraggedNodes[Idx]->GetNodeObj());
			DraggedTestNode->Modify();
			DraggedTestNode->SetParentNodeForSubNode(DropTargetParentNode);

			DropTargetParentNode->Modify();
			DropTargetParentNode->InsertSubNodeAt(DraggedTestNode, InsertIndex);