#include <QtCore/QDebug>
#include <QtGui/QApplication>
#include <QtGui/QDragMoveEvent>
#include <QtGui/QPainter>
#include <QtGui/QTreeWidget>

class TreeWidget : public QTreeWidget
{
public:
	TreeWidget( QWidget* parent = 0 )
		: QTreeWidget( parent ),
		_dragMoveItemBelow( 0 )
	{
		setDragDropMode( QTreeWidget::InternalMove );
	}

	~TreeWidget() {}

private:
	void dragMoveEvent( QDragMoveEvent* event )
	{
		_dragMoveLine = QLine();
		event->ignore();

		QTreeWidgetItem* item = itemFromIndex( indexAt( event->pos() ) );
		if ( item == currentItem() ) {
			return;
		}

		const QRect& rect = visualRect( indexAt( event->pos() ) );
		if ( rect.top() + 2 >= event->pos().y() ) {
			if ( currentItem() == itemAbove( item ) ) {
				return;
			}

			_dragMoveLine = QLine( rect.left(), rect.top(), rect.right(), rect.top() );
			_dragMoveItemBelow = item;
			event->acceptProposedAction();
		} else if ( rect.bottom() - 2 <= event->pos().y() ) {
			if ( currentItem() == itemBelow( item ) ) {
				return;
			}

			_dragMoveLine = QLine( rect.left(), rect.bottom(), rect.right(), rect.bottom() );
			_dragMoveItemBelow = itemBelow( item );
			event->acceptProposedAction();
		}

		viewport()->update();
	}

	void dropEvent( QDropEvent* )
	{
		QTreeWidgetItem* item = currentItem();
		item = takeTopLevelItem( indexOfTopLevelItem( item ) );

		insertTopLevelItem( indexOfTopLevelItem( _dragMoveItemBelow ), item );
		setCurrentItem( item );

		_dragMoveLine = QLine();
		viewport()->update();
	}

	void paintEvent( QPaintEvent* event )
	{
		QTreeWidget::paintEvent( event );

		QPainter p( viewport() );
		p.setPen( QPen( Qt::black, 2 ) );
		p.drawLine( _dragMoveLine );
	}

	QLine _dragMoveLine;
	QTreeWidgetItem* _dragMoveItemBelow;
};

int main( int argc, char** argv )
{
	QApplication app( argc, argv );

	TreeWidget widget;
	widget.setColumnCount( 1 );
	widget.headerItem()->setText( 0, QObject::tr( "Title" ) );

	QTreeWidgetItem* item1 = new QTreeWidgetItem( &widget );
	item1->setText( 0, "1" );

	QTreeWidgetItem* item2 = new QTreeWidgetItem( &widget );
	item2->setText( 0, "2" );

	QTreeWidgetItem* item3 = new QTreeWidgetItem( &widget );
	item3->setText( 0, "3" );

	QTreeWidgetItem* item4 = new QTreeWidgetItem( &widget );
	item4->setText( 0, "4" );

	QTreeWidgetItem* item5 = new QTreeWidgetItem( &widget );
	item5->setText( 0, "5" );

	app.setActiveWindow( &widget );
	widget.show();

	return app.exec();
}