Qt5 QStyledItemDelegate on a QListView removes all the default style - c++

Question

I have some QIcon and QString pairs displayed in a QListview. The whole thing has been set up using the Qt Model/View Programming.
I am displaying labeled icons in this QListView. Items are displayed using the IconMode, Snap and TopToBottom flags. Thus, these are organised into a grid.
I would like to layout all the QListView items vertically and centered. In order to do this, I subclassed the QStyledItemDelegate object, and overloaded the paint method. However, I have three main problems:
Icon labels have been moved (in the QStyledItemDelegate subclasses) and a dotted square appears at its original place.
All the default styles are gone (hover, selection). I know how I can add some again, but I would like to use the default one (Windows style).
Everything is rendered into a grid, even if setGridSize is not called. I would like to use only one "column".
Here is a piece of code:
An extract of the constructor of my custom QListView:
setViewMode(QListView::IconMode);
setMovement(QListView::Snap);
setFlow(QListView::TopToBottom);
setSpacing(5);
setIconSize(QSize(iconSize, iconSize));
setGridSize(QSize(iconSize + 10, iconSize + 10));
setDragEnabled(true);
setAcceptDrops(true);
setDropIndicatorShown(true);
The paint method of the QStyledItemDelegate:
void FramesStyledItemDelegate::paint(QPainter* painter, const QStyleOptionViewItem& option, const QModelIndex& index) const
{
QStyleOptionViewItemV4 opt = option;
//initStyleOption(&opt, index);
opt.icon = QIcon();
opt.text = QString();
QApplication::style()->drawControl(QStyle::CE_ItemViewItem, &opt, painter);
const QRect r = option.rect;
QIcon icon = qvariant_cast<QIcon>(index.data(Qt::DecorationRole));
QString string = qvariant_cast<QString>(index.data(Qt::DisplayRole));
QPixmap pix = icon.pixmap(r.size());
const QPoint p = QPoint((r.width() - pix.width())/2, (r.height() - pix.height())/2);
painter->drawPixmap(r.topLeft() + p, pix);
painter->drawText(r.center() + p + QPoint(-(string.count() / 2), r.height() / 2), string);
}
If I do not use the initStyleOption shown above, I can remove the
dotted square, but I lose all the default styles.
If I uncomment the initStyleOption, The dotted square appears. I also lose all the default styles.
Here are some screenshots:
The cursor is on item 0 (No hover decoration, no selection decoration).
Item 0 has been selected. A small dotted square appears (initStyleOption has been uncommented).
I have switched to the ListMode. Selection decoration is working but not hover. Again, a small dotted square appears at the original place of the label.
Does someone have an idea? Thanks for your answers.