How to override (re-implement) a member function in QFileSystemModel

c++, class, overriding, qt

Solution

Looks like this was anticipated, as there is a method for setting the "icon provider":

http://doc.qt.io/archives/qt-4.7/qfilesystemmodel.html#setIconProvider

The parameter, a `QFileIconProvider`, looks to be a fairly simple class that you can implement an instance of yourself, with a method that fetches an icon from a `QFileInfo` (basically, a file name):

http://doc.qt.io/archives/qt-4.7/qfileinfo.html

You could implement one of these that just returns the same icon for everything. If you find that doesn't address your problem, the following compiled fine for me...FWIW:

class FileModel : public QFileSystemModel {
public:
    QVariant data(const QModelIndex &index, int role) const
    {
        if (role == Qt::DecorationRole) {
            return QVariant (QIcon ());
        }    

        return QFileSystemModel::data(index, role);
    }
};

Problem

I've been struggling with this for a while. Qt's `QFileSystemModel` is really slow when fetching several hundred files because of a really bad icon fetching algorithm. I want to completely disable icons. They are fetched in `QFileSystemModel::data` method which is not virtual (the source of QFileSystemModel is available here: http://qt.gitorious.org/qt/qt/blobs/4.7/src/gui/dialogs/qfilesystemmodel.cpp) This is the code I'm trying to run: ``` class FileModel : public QFileSystemModel { using QFileSystemModel::data; public: QVariant QFileSystemModel::data(const QModelIndex &index, int role) const { // my own implementation here } } ``` but it fails with `cannot define member function QFileSystemModel::data witin FileModel` UPDATE I've managed to override the function and this is what I have now: ``` class FileModel : public QFileSystemModel { public: QVariant data(const QModelIndex &index, int role) const { // Here goes Qt's implementation Q_D(const QFileSystemModel); if (!index.isValid() || index.model() != this) return QVariant(); switch (role) { case Qt::EditRole: case Qt::DisplayRole: switch (index.column()) { case 0: return d->name(index); case 1: return d->size(index); case 2: return d->type(index); case 3: return d->time(index); default: qWarning("data: invalid display value column %d", index.column()); break; } break; case FilePathRole: return filePath(index); case FileNameRole: return d->name(index); case Qt::DecorationRole: if (index.column() == 0) { QIcon icon = d->icon(index); // This is the part I need to change if (icon.isNull()) { if (d->node(index)->isDir()) icon = d->fileInfoGatherer.iconProvider()->icon(QFileIconProvider::Folder); else icon = d->fileInfoGatherer.iconProvider()->icon(QFileIconProvider::File); } return icon; } break; case Qt::TextAlignmentRole: if (index.column() == 1) return Qt::AlignRight; break; case FilePermissions: int p = permissions(index); return p; } return QVariant(); } }; ``` However this code doesn't compile. This is the error I get: `'const QFileSystemModelPrivate* QFileSystemModel::d_func() const' is private`

Original source