Using QSortFilterProxyModel with a tree model

Question

I have a QDirModel whose current directory is set. Then I have a QListView which is supposed to show the files in that directory. This works fine.

Now I want to limit the files shown, so it only shows png files (the filename ends with .png). The problem is that using a QSortFilterProxyModel and setting the filter regexp will try to match every parent of the files as well. According to the documentation:

For hierarchical models, the filter is applied recursively to all children. If a parent item doesn't match the filter, none of its children will be shown.

So, how do I get the QSortFilterProxyModel to only filter the files in the directory, and not the directories it resides in?

Answer 1

Just use KRecursiveFilterProxyModel model from the KItemModels KDE API

Answer 2

We ran into something similar where I work, and ended up making our own proxy model to do our filtering. However, looking through the documentation for what you want (which seems like it would be a more common case), I came across two possibilities.

1. You might be able to set a name filter on the QDirModel and filter things that way. I have no idea if this will work like you want, or if the name filters apply to directories also. The documentation is kind of sparse on these.
2. Subclass the QSortFilterProxyModel and override the filterAcceptsRow function. From the documentation:

Custom filtering behavior can be achieved by reimplementing the filterAcceptsRow() and filterAcceptsColumn() functions.

Then you could presumably use the model index to check if the index item is a directory (automatically accept) or a file (filter on filename).

Answer 3

For people like me who are interested in the following behaviour : if a child matches the filter, then its ancestors should not be hidden :

bool MySortFilterProxyModel::filterAcceptsRow(int source_row, const QModelIndex & source_parent) const
{
    // custom behaviour :
    if(filterRegExp().isEmpty()==false)
    {
        // get source-model index for current row
        QModelIndex source_index = sourceModel()->index(source_row, this->filterKeyColumn(), source_parent) ;
        if(source_index.isValid())
        {
            // if any of children matches the filter, then current index matches the filter as well
            int i, nb = sourceModel()->rowCount(source_index) ;
            for(i=0; i<nb; ++i)
            {
                if(filterAcceptsRow(i, source_index))
                {
                    return true ;
                }
            }
            // check current index itself :
            QString key = sourceModel()->data(source_index, filterRole()).toString();
            return key.contains(filterRegExp()) ;
        }
    }
    // parent call for initial behaviour
    return QSortFilterProxyModel::filterAcceptsRow(source_row, source_parent) ;
}

Answer 4

As of Qt 5.10, QSortFilterProxyModel has the option to filter recursively. In other words, if a child matches the filter, its parents will be visible as well.

Check out QSortFilterProxyModel::recursiveFilteringEnabled.

Answer 5

derive qsortfilterproxymodel and then...

bool YourQSortFilterProxyModel::filterAcceptsRow ( int source_row, const QModelIndex & source_parent ) const
{
    if (source_parent == qobject_cast<QStandardItemModel*>(sourceModel())->invisibleRootItem()->index())
    {
        // always accept children of rootitem, since we want to filter their children 
        return true;
    }

    return QSortFilterProxyModel::filterAcceptsRow(source_row, source_parent);
}