Use of QAbstractItemDelegate::closeEditor

[jml]

I'm trying to user input perform validation in a QTableView/QAbstractTableModelstructure. I want to keep the cursor in a table cell if the entry is invalid. The only thing I've found that seems to work is

void DoubleEditDelegate::setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const
{	
	QString data = static_cast<QLineEdit*>(editor)->text();
	int pos;
	QValidator::State state = validator_->validate(data, pos);
	if (validator_->validate(data, pos) == QValidator::Acceptable)
	{
		model->setData(index, data);
		emit const_cast<DoubleEditDelegate*>(this)->clearMessage();
	}
	else
	{
		emit const_cast<DoubleEditDelegate*>(this)->errorMessage("Double required at line " + QString::number(index.row()+1));
		emit const_cast<DoubleEditDelegate*>(this)->closeEditor(editor, QAbstractItemDelegate::EditPreviousItem);
	}	
}

void DoubleEditDelegate::setModelData(QWidget *editor, QAbstractItemModel *model, const QModelIndex &index) const
{	
	QString data = static_cast<QLineEdit*>(editor)->text();
	int pos;
	QValidator::State state = validator_->validate(data, pos);
	if (validator_->validate(data, pos) == QValidator::Acceptable)
	{
		model->setData(index, data);
		emit const_cast<DoubleEditDelegate*>(this)->clearMessage();
	}
	else
	{
		emit const_cast<DoubleEditDelegate*>(this)->errorMessage("Double required at line " + QString::number(index.row()+1));
		emit const_cast<DoubleEditDelegate*>(this)->closeEditor(editor, QAbstractItemDelegate::EditPreviousItem);
	}	
}

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This doesn't seem right - having to const_cast the "this" pointer. Is this the correct way to use the closeEditor signal? If not, how do I do this?

Thanks for any help.