add comobox as the header of QTableWidget

how to add the comobox in the header of the QTableWidget;,and how to control the TableWidget's rows and columns just by click the scroll button at the both side of the scroll bar.
i use the the wheel event to add rows ,but i can't find how to know the wheel's direction

Code:

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void DataEditor::wheelEvent(QWheelEvent *e)
{
 
 
 
 
	if (table->verticalScrollBar()->value()==table->verticalScrollBar()->maximum())
	{
		int count=table->rowCount()+1;
		table->setRowCount(count);
	}
	if (table->verticalScrollBar()->value()==table->verticalScrollBar()->minimum())
	{
 
		if ((table->verticalScrollBar()->value())>20)
		{	int count=table->rowCount()-1;
		table->setRowCount(count);			
		}
 
 
	}
}

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