QAbstractItemModel derivative showing a checkbox next to each index

[i92guboj]

Hello.

I am creating an FtpFileSystemModel, and, for that, I am using QAbstractItemModel as a base, which I have never subclassed before.

After quite a few problems I have reached the point where my ftp files are displayed in a QTreeView, just like a QFileSystemModel would do with a local fs.

There are a few quirks here and there, though. The thing that worries me is that all the indexes (or "cells"), show a ticker next to them. This is better illustrated with a screenshot:

20140517.122325.jpg

See the ftp file listing to the middle-right portion of the screenshot.

Before you ask, the flags() method is this:

Qt::ItemFlags FtpFileSystemModel::flags(const QModelIndex &index) const
{
    if(!index.isValid())
    {
        return 0;
    }
 
    Qt::ItemFlags flags = Qt::ItemIsEnabled | Qt::ItemIsSelectable;
    qDebug() << Q_FUNC_INFO << QString("flags: %1").arg(flags);
    return flags;
}

Qt::ItemFlags FtpFileSystemModel::flags(const QModelIndex &index) const
{
    if(!index.isValid())
    {
        return 0;
    }

    Qt::ItemFlags flags = Qt::ItemIsEnabled | Qt::ItemIsSelectable;
    qDebug() << Q_FUNC_INFO << QString("flags: %1").arg(flags);
    return flags;
}

To copy to clipboard, switch view to plain text mode 

As you see, neither of Qt::ItemIsUserCheckable or Qt::ItemIsTristate is set.

I have also a problem with alignment, but I haven't dug much into it. I am setting these in data(), but they don't seem to do anything:

if(role == Qt::TextAlignmentRole)
    {
        Qt::Alignment flags = 0;
 
        if(index.column() == 0 || index.column() == 1)
        {
            flags = Qt::AlignVCenter | Qt::AlignLeft;
        }
        else
        {
            flags = Qt::AlignVCenter | Qt::AlignRight;
        }
    }

if(role == Qt::TextAlignmentRole)
    {
        Qt::Alignment flags = 0;

        if(index.column() == 0 || index.column() == 1)
        {
            flags = Qt::AlignVCenter | Qt::AlignLeft;
        }
        else
        {
            flags = Qt::AlignVCenter | Qt::AlignRight;
        }
    }

To copy to clipboard, switch view to plain text mode 

Thanks for any idea you can share

[anda_skoa]

This is most likely unrelated to flags() or alignment, the most likely cause is that your data() method returns something other than a null QVariant when it is asked for the CheckStateRole.

A common mistake is to forget to check the "role" argument that is passed to data().

Cheers,
_

[i92guboj]

It worked like a charm. Thanks.

But.... out of curiosity, how are you supposed to know that? I can't see that info in the subclassing document for QAbstractItemModel not even in the internet...

Again, thank you

[anda_skoa]

The API contract of the data() method is that it returns a null variant for all indexes or roles that it does not have actual data for.

From QAbstractItemModel::data()

Note: If you do not have a value to return, return an invalid QVariant instead of returning 0.

Cheers,
_

[i92guboj]

Ok. Thanks. Now I think I fully got it. Some more checks are due now in my code :lol:

Thank you.