Enhancing thumbnails with PictureDelegate

By default, a QListView class will request Qt::DisplayRole and Qt::DecorationRole to display text and a picture for each item. Thus, we already have a visual result, for free, that looks like this:

However, our Gallery application deserves better thumbnail rendering. Hopefully, we can easily customize it using the view's delegate concept. A QListView class provides a default item rendering. We can do our own item rendering by creating a class that inherits QStyledItemDelegate. The aim is to paint your dream thumbnails with a name banner like the following screenshot:

Let's take a look at PictureDelegate.h:

#include <QStyledItemDelegate> 
 
class PictureDelegate : public QStyledItemDelegate 
{ 
    Q_OBJECT 
public: 
    PictureDelegate(QObject* parent = 0); 
 
    void paint(QPainter* painter, const QStyleOptionViewItem& 
        option, const QModelIndex& index) const override; 
 
    QSize sizeHint(const QStyleOptionViewItem& option...