Custom sortable columns in QFileSystemModel

[JonB]

@Jo-Jo
Well, start by checking that goes through the toDateTime() path, what their values are and that is getting it right. I don't know what is wrong just by looking at it.

Btw, check whether the QString::localeAwareCompare(0 is case insensitive or case sensitive? Windows, but not Linux, sorts case insensitively, yours might not.

You have just updated your code: I'm not sure it is any different from what you first wrote, but if it is and works that's fine.

[Jo Jo]

@JonB Everything worked except for the "Date Modified" column. It turned out that Qt returns this date as a QString. I had to convert this string to QDateTime. Now the code looks like this:

class CustomSortFilterProxyModel : public QSortFilterProxyModel
{
    QList<int> m_dtCols{3,4};
public:
    explicit CustomSortFilterProxyModel(QObject *parent = nullptr) : QSortFilterProxyModel(parent) {}

protected:
    bool lessThan(const QModelIndex &left, const QModelIndex &right) const override
    {
        auto model = (QFileSystemModel*)sourceModel();
        bool isLeftDir = model->isDir(left);
        bool isRightDir = model->isDir(right);

        if ((isLeftDir && isRightDir) || (!isLeftDir && !isRightDir))
        {
            auto leftName  = model->data(left,  Qt::DisplayRole);
            auto rightName = model->data(right, Qt::DisplayRole);

            //return (leftName.toDateTime() < rightName.toDateTime()); // OK, works fine for dates

            if (m_dtCols.contains(sortColumn()))
            {
                if (sortColumn() == 3)
                {
                    QDateTime dt1 = QDateTime::fromString(leftName.toString(), "M/d/yyyy h:mm AP");
                    QDateTime dt2 = QDateTime::fromString(rightName.toString(), "M/d/yyyy h:mm AP");
                    return dt1 < dt2;
                }

                return (leftName.toDateTime() < rightName.toDateTime());
            }

            const int compare = QString::localeAwareCompare(leftName.toString(), rightName.toString());

            if(compare != 0) {
                return compare < 0;
            }
        }
        else if (isLeftDir)
        {
            return true;
        }

        return false;
    }
};

However, I'm not sure that I'm setting the date format correctly. It can change depending on the OS settings, or am I wrong?

[Christian Ehrlicher]

@Jo-Jo said in Custom sortable columns in QFileSystemModel:

I had to convert this string to QDateTime

You already converted the QVariant to a QDateTime above - so why do you use the way through QString now again?

[Jo Jo]

@Christian-Ehrlicher said in Custom sortable columns in QFileSystemModel:

You already converted the QVariant to a QDateTime above - so why do you use the way through QString now again?

Because "Date Modified" column is created by Qt and Qt using QString for this column. If I convert QVariant to QDateTime, in this case comparison does not work properly

[Christian Ehrlicher]

Then you should debug why ... e.g. with a qDebug() statement as @JonB already wrote some time ago....

[JonB]

@Jo-Jo said in Custom sortable columns in QFileSystemModel:

Everything worked except for the "Date Modified" column. It turned out that Qt returns this date as a QString.

I am surprised at this, but untested. You are now talking about a "Date Modified" column inbuilt into QFileSystemModel, and not the "creation date" column you added for your birthTime()? But that is QDateTime QFileSystemModel::lastModified(). So I don't understand where you are getting any string for a datetime which you need to convert.

[Jo Jo]

@JonB said in Custom sortable columns in QFileSystemModel:

You are now talking about a "Date Modified" column inbuilt into QFileSystemModel, and not the "creation date" column you added for your birthTime()?

Yes. This column value is QString, not QDateTime. You may check sources: https://codebrowser.dev/qt5/qtbase/src/widgets/dialogs/qfilesystemmodel.cpp.html#808

[Christian Ehrlicher]

Thast's why https://doc.qt.io/qt-6/qfilesystemmodel.html#lastModified is there.

[JonB]

@Jo-Jo
I now see that, and see from https://codebrowser.dev/qt5/qtbase/src/widgets/dialogs/qfilesystemmodel.cpp.html#737 that it is called in the implementation of QFileSystemModel::data() for column #3, which is what I needed to know.

I also see it is formatted as a string with QLocale::ShortFormat. I don't know what that looks like, I don't know how "precise" it is (e.g. down to, say, milliseconds or likely not?), I don't know what the locale-aware formatting does with it. Putting all these together it would not surprise me if it is unsuitable for sorting, and/or for converting back (accurately) to a datetime/comparing. Whereas the birthTime() you use for your extra column is indeed a datetime type and is suitable.

Hence, as both I and @Christian-Ehrlicher have said, I would use lastModified() just as you use birthDate() for this column in your own code for data() method.

[Jo Jo]

@Christian-Ehrlicher @JonB agree with you guys about lastModified, thanks!