Optimizing filterAcceptsRow() to filter a tree

[vfernandez]

I have a custom QSortFilterProxyModel that's being used with a custom model and a QTreeView. Through a QLineEdit and the corresponding signal/slot connection, it allows the user to search for something in the tree of the model and also to hide/show comments which are also nodes in the tree. This is the code:

ParsedTreeFilterProxyModel::ParsedTreeFilterProxyModel(QObject *parent)
 : QSortFilterProxyModel(parent)
{
	m_commentsVisible = true;
}
 
 
bool ParsedTreeFilterProxyModel::commentsVisible()
{
	return m_commentsVisible;
}
 
 
void ParsedTreeFilterProxyModel::setCommentsVisible(bool visible)
{
	m_commentsVisible = visible;
	filterChanged();
}
 
 
bool ParsedTreeFilterProxyModel::filterAcceptsRow(int sourceRow, const QModelIndex &sourceParent) const
{
	QString name = sourceModel()->data( sourceModel()->index(sourceRow, 0, sourceParent) ).toString();
	QString value = sourceModel()->data( sourceModel()->index(sourceRow, 1, sourceParent) ).toString();
	QString type = sourceModel()->data( sourceModel()->index(sourceRow, 0, sourceParent), Qt::UserRole ).toString();
	bool isComment = (type == "ConfigNode");
	return ( (!isComment || m_commentsVisible) && (name.contains(filterRegExp()) || value.contains(filterRegExp())) );
}

ParsedTreeFilterProxyModel::ParsedTreeFilterProxyModel(QObject *parent)
 : QSortFilterProxyModel(parent)
{
	m_commentsVisible = true;
}


bool ParsedTreeFilterProxyModel::commentsVisible()
{
	return m_commentsVisible;
}


void ParsedTreeFilterProxyModel::setCommentsVisible(bool visible)
{
	m_commentsVisible = visible;
	filterChanged();
}


bool ParsedTreeFilterProxyModel::filterAcceptsRow(int sourceRow, const QModelIndex &sourceParent) const
{
	QString name = sourceModel()->data( sourceModel()->index(sourceRow, 0, sourceParent) ).toString();
	QString value = sourceModel()->data( sourceModel()->index(sourceRow, 1, sourceParent) ).toString();
	QString type = sourceModel()->data( sourceModel()->index(sourceRow, 0, sourceParent), Qt::UserRole ).toString();
	bool isComment = (type == "ConfigNode");
	return ( (!isComment || m_commentsVisible) && (name.contains(filterRegExp()) || value.contains(filterRegExp())) );
}

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Nothing special but as you may guess, when I search for something it only displays the nodes from the top level. When a node is inside some subtree, the parent tree nodes aren't displayed (as the documentation states). Now I want to make it work as it should: display a tree node if there's some child somewhere in its subtree that matches the filter.

The question is: when filterAcceptsRow() is processing one of those parent tree nodes, do I have to search for nodes that match the filter through the whole subtree (which is obviously very inefficient and time-consuming) or is there a better, more efficient, way to do it? I could think of moving through the tree and when a node matches the filter marking all the parent nodes as "visible" or something like that but AFAIK it's not possible with filterAcceptsRow(). Is it?

P.S.: I'm using Qt 4.2.