I implementing a custom QStyledItemDelegate and want to know decoration QRect in sizeHint() method to calculate correct size hint for my items.

I tried:

QSize
WordWrapItemDelegate::sizeHint( const QStyleOptionViewItem & option,
    const QModelIndex & index ) const
{
    QStyleOptionViewItem opt = option;
    initStyleOption( &opt, index );
    opt.rect = { 0, 0, m_parent->header()->sectionSize( index.column() ), 0 };
    
    QStyle * style = opt.widget ? opt.widget->style() : QApplication::style();
    auto iconRect = style->subElementRect( QStyle::SE_ItemViewItemDecoration, &opt, opt.widget );
    
    qDebug() << iconRect;
    
    return option.fontMetrics.boundingRect(
        QRect( 0, 0,
            m_parent->header()->sectionSize( index.column() ) -
                option.decorationSize.width() /** level * 2*/, 0 ),
        Qt::AlignLeft | Qt::TextWordWrap,
        index.data( Qt::DisplayRole ).toString() ).size();
}

And:

QSize
WordWrapItemDelegate::sizeHint( const QStyleOptionViewItem & option,
    const QModelIndex & index ) const
{
    int level = 1;
    auto i = index;
    
    while( i.parent().isValid() )
    {
        ++level;
        i = i.parent();
    }
    
    return option.fontMetrics.boundingRect(
        QRect( 0, 0,
            m_parent->header()->sectionSize( index.column() ) -
                option.decorationSize.width() * level * 2, 0 ),
        Qt::AlignLeft | Qt::TextWordWrap,
        index.data( Qt::DisplayRole ).toString() ).size();
}

The second variant works, but, as you can see, I use some hard-coding option.decorationSize.width() * level * 2.

In the first variant in iconRect set Y only, but I need a width of a decoration.

Do anybody know how to know the width of the decoration in item?