Strayer

#include <QtCore>#include <QtGui>class CheckboxProxyModel : public QSortFilterProxyModel{public:	CheckboxProxyModel(QObject *parent = 0) : QSortFilterProxyModel(parent) {}	QVariant data(const QModelIndex &index, int role) const	{		if (index.column() < 3)		{			if (role == Qt::DisplayRole)				return QString("Checkbox %1").arg(index.column()+1);			else				return QVariant();		}		else			return QSortFilterProxyModel::data(index, role);	}	QVariant headerData(int section, Qt::Orientation orientation, int role) const	{		if (section < 3)		{			if (role == Qt::DisplayRole)				return QString("Hallo Welt!");			else				return QVariant();		}		else			// headerData uses mapToSource with section as the row parameter			// so I don't need to decrement section by three			return QSortFilterProxyModel::headerData(section, orientation, role);	}	QModelIndex mapToSource(const QModelIndex &proxyIndex) const	{		if (proxyIndex.column() < 3)			return QModelIndex();		else		{			QModelIndex tmp = QSortFilterProxyModel::index(proxyIndex.row(), proxyIndex.column()-3, proxyIndex.parent());			return QSortFilterProxyModel::mapToSource(tmp);		}	}	QModelIndex mapFromSource(const QModelIndex &sourceIndex) const	{		return QSortFilterProxyModel::index(sourceIndex.row(), sourceIndex.column()+3, sourceIndex.parent());	}	int columnCount(const QModelIndex &parent) const	{		return QSortFilterProxyModel::columnCount(parent)+3;	}};int main(int argc, char *argv[]){	QApplication a(argc, argv);	// Create view and model	QTreeView *view = new QTreeView();	QFileSystemModel *model = new QFileSystemModel(view);	// Get a root path for the model	QString rootPath = QFileDialog::getExistingDirectory(view, "Choose directory");	if (rootPath.isEmpty())	{		QMessageBox::critical(view, "Error!", "You did not choose a directory!");		return -1;	}	QModelIndex rootModelIndex = model->setRootPath(rootPath);	// Create proxy model	CheckboxProxyModel *proxyModel = new CheckboxProxyModel(view);	proxyModel->setSourceModel(model);	view->setModel(proxyModel);	// Set the root index of the view to the root path of the model	view->setRootIndex(proxyModel->mapFromSource(rootModelIndex));	view->show();	return a.exec();}