Add column to proxied Model

krzysieklfc

I have subclassed a QIdentityProxyModel which proxies QFileSystemModel and which I use in a QTableView. Now, I want to append the 4th column at the end.

I followed the sugestions described here:

I incremented the return value of columnCount() - this results in a blank, glitched column.
I implemented index() with the following:

QModelIndex ModelProxy::index(int row, int column, const QModelIndex& parent) const {
	if (column == 4) 
		return createIndex(row, column);

        auto proxyRootIndex = mapFromSource(fs()->QFileSystemModel::index(fs()->rootPath()));
	return QIdentityProxyModel::index(row, column, proxyRootIndex);
}

But this gives me access violation error when I'm creating these indexes.

I realize there are already some threads addressing the same issue, but they did not help me so I would appreciate if anyone could point out what I'm missing.

Here's my code:

class ModelProxy : public QIdentityProxyModel
{
public:

	ModelProxy(QObject* parent = nullptr);
	QVariant data(const QModelIndex& index, int role = Qt::DisplayRole) const override;

	virtual QVariant headerData(int section, Qt::Orientation orientation = Qt::Horizontal, int role = Qt::DisplayRole) const override;
	virtual int columnCount(const QModelIndex& parent = QModelIndex()) const override;
	virtual int rowCount(const QModelIndex& parent = QModelIndex()) const override;
	QModelIndex setRootPath(const QString& path) { return fs()->setRootPath(path); };
	QString getRootPath() { return fs()->rootPath(); };
	QModelIndex getRootIndex() { return mapFromSource(fs()->QFileSystemModel::index(fs()->rootPath())); };

	virtual QModelIndex index(int row, int column, const QModelIndex& parent = QModelIndex()) const override;

private:
	Q_OBJECT

	QFileSystemModel* fs() const { return qobject_cast<QFileSystemModel*>(sourceModel()); }

	QMultiMap<QString, QVariant> m_icon, m_width, m_height, m_type, m_channels, m_size;

signals:
	void rootPathChanged(const QString&);
};


ModelProxy::ModelProxy(QObject* parent)
	: QIdentityProxyModel(parent)
{
	setSourceModel(new QFileSystemModel(this));
	fs()->setReadOnly(true);
	fs()->setFilter(QDir::NoDotAndDotDot | QDir::Files);
	auto filters = QStringList{ "*.exr", "*.EXR", "*.hdr", "*.HDR" };
	fs()->setNameFilters(filters);
	fs()->setNameFilterDisables(false);


	connect(fs(), &QFileSystemModel::rootPathChanged,
		this, &ModelProxy::rootPathChanged);
}

QModelIndex ModelProxy::index(int row, int column, const QModelIndex& parent) const {
	auto proxyRootIndex = mapFromSource(fs()->QFileSystemModel::index(fs()->rootPath()));

	if (column == 4) {
		return createIndex(row, column);
	}
	return QIdentityProxyModel::index(row, column, proxyRootIndex);
}

int ModelProxy::columnCount(const QModelIndex&) const {
	QModelIndex proxyRootIndex = mapFromSource(fs()->QFileSystemModel::index(fs()->rootPath()));
	return QIdentityProxyModel::columnCount(proxyRootIndex) + 1;
}

int ModelProxy::rowCount(const QModelIndex&) const {
	QModelIndex proxyRootIndex = mapFromSource(fs()->QFileSystemModel::index(fs()->rootPath()));
	return QIdentityProxyModel::rowCount(proxyRootIndex);
}

QVariant ModelProxy::headerData(int index, Qt::Orientation orient, int role) const {
	return QIdentityProxyModel::headerData(index, orient, role);
}

QVariant ModelProxy::data(const QModelIndex& index, int role) const
{
	qDebug() << "data " << index.row() << index.column();

	switch (role) {
	case QFileSystemModel::FileIconRole:
	{
		if (index.column() == 0) {
			auto const path = QString{ index.data(QFileSystemModel::FilePathRole).toString() };

			if (QFile::exists(path) && path.toLower().endsWith(".exr") || path.toLower().endsWith(".hdr")) {
				if (m_icon.contains(path))
					return m_icon.value(path);
				else {
					QPersistentModelIndex pIndex = index;
					emit hasIcon(path, QIdentityProxyModel::data(index, role).value<QIcon>(), pIndex);

					QThreadPool::globalInstance()->setMaxThreadCount(1);
					QtConcurrent::run([this, path, pIndex, role] {
						emit hasIcon(path, QIcon{ ":/resources/img/arrow_icon.png" }, pIndex);
						emit hasIcon(path, loadHDRtoIcon(path, pIndex), pIndex);
					});
				}
			}
			else
				return QIdentityProxyModel::data(index, role);
		}
	}

	case Qt::DisplayRole:
	{
		auto const path = QString{ index.data(QFileSystemModel::FilePathRole).toString() };

		switch (index.column()) {
		case 1:
		{
			if (m_type.contains(path))
				return m_type.value(path);
			else return QVariant{};
		}
		case 2:
		{
			if (m_channels.contains(path))
				return m_channels.value(path);
			else return QVariant{};
		}
		case 3:
		{
			if (m_width.contains(path) && m_height.contains(path))
				return m_width.value(path).toString() + "x" + m_height.value(path).toString();
			else return QVariant{};
		}
		case 4:
		{
			if (m_size.contains(path))
				return m_size.value(path);
			return QString{ "test" };
		}
		default: return QIdentityProxyModel::data(index, role);
		}
	}
	}
	return QIdentityProxyModel::data(index, role);
}

Christian Ehrlicher

@krzysieklfc said in Add column to proxied Model:

But this gives me access violation error when I'm creating these indexes.

Please provide a backtrace for this. I would guess it's an assertion rather than a crash.
And your rowCount() doesn't look correct - since it's a tree it's important to pass the correct parent instead simply using the rootPath. The same goes for columnCount

krzysieklfc

@christian-ehrlicher Hello,

The exception occurs at the last line of ModelProxy::data(), in return QIdentityProxyModel::data(index, role);
when data() is called for the 0th row and 4th column.

Exception thrown at 0x00007FFE0B373D4A (Qt5Widgets.dll) in 3dsmax.exe: 0xC0000005: Access violation reading location 0x0000000000000030.

I reimplemented columnCount() and rowCount() to use parent, but the result is the same. I'm not sure if this is correct though.

int ModelProxy::columnCount(const QModelIndex& parent) const {
	auto sp = mapToSource(parent);
	if (sp.isValid() && sp.model())
		return (sp.model()->columnCount(sp) + 1);
	return 0;
}

int ModelProxy::rowCount(const QModelIndex& parent) const {
	auto sp = mapToSource(parent);
	if (sp.isValid() && sp.model())
		return sp.model()->rowCount(sp);
	return 0;
}

Christian Ehrlicher

Please provide a backtrace for the exception. For me it looks like your're working on an invalid instance of the class.

AsevaPliuha

It seems you're trying to append a 4th column to a QIdentityProxyModel that proxies a QFileSystemModel and is being used in a QTableView. You've tried incrementing the return value of column Count() and implementing index() as described in the linked thread, but are still running into issues. One thing to keep in mind is that when working with proxy models, it's important to ensure that the index mappings are properly set up and that the data is being correctly passed through the proxy. If the above methods did not help you, it's possible that there is an issue with the way the proxy model is being set up or configured. It would be best to check the documentation and make sure that the proxy model is properly configured. Another solution you can look into is using fast residential proxies to access your data in a different way, but it's not related to your current problem.