QModelIndex{
    int r, c;
    quintptr i;
    const QAbstractItemModel *m;
    inline QModelIndex QModelIndex::parent() const
    { return m ? m->parent(*this) : QModelIndex(); }

    inline QVariant QModelIndex::data(int arole) const
    { return m ? m->data(*this, arole) : QVariant(); }
}

QPersistentModelIndex{
    QPersistentModelIndexData *d;
}
QPersistentModelIndexData{
    QModelIndex index;
    QAtomicInt ref;
}

// model 不存储数据 只是定义了操作数据的接口
// 但是抽象出了持久引用，保存持久引用结构
QAbstractItemModelPrivate{
    struct Change {
        Q_DECL_CONSTEXPR Change() : parent(), first(-1), last(-1), needsAdjust(false) {}
        Q_DECL_CONSTEXPR Change(const QModelIndex &p, int f, int l) : parent(p), first(f), last(l), needsAdjust(false) {}

        QModelIndex parent;
        int first, last;


        // In cases such as this:
        // - A
        // - B
        // - C
        // - - D
        // - - E
        // - - F
        //
        // If B is moved to above E, C is the source parent in the signal and its row is 2. When the move is
        // completed however, C is at row 1 and there is no row 2 at the same level in the model at all.
        // The QModelIndex is adjusted to correct that in those cases before reporting it though the
        // rowsMoved signal.
        bool needsAdjust;

        Q_DECL_CONSTEXPR bool isValid() const { return first >= 0 && last >= 0; }
    };
    QStack<Change> changes;
    struct Persistent {
        Persistent() {}
        QMultiHash<QModelIndex, QPersistentModelIndexData *> indexes;
        QStack<QVector<QPersistentModelIndexData *> > moved;
        QStack<QVector<QPersistentModelIndexData *> > invalidated;
        void insertMultiAtEnd(const QModelIndex& key, QPersistentModelIndexData *data);
    } persistent;
    Qt::DropActions supportedDragActions;
    QHash<int,QByteArray> roleNames;
}

QHash<QModelIndex, QPersistentModelIndexData *> &indexes = model->d_func()->persistent.indexes;


qnamespace.h

    enum ItemDataRole {
        DisplayRole = 0,
        DecorationRole = 1,
        EditRole = 2,
        ToolTipRole = 3,
        StatusTipRole = 4,
        WhatsThisRole = 5,
        // Metadata
        FontRole = 6,
        TextAlignmentRole = 7,
        BackgroundRole = 8,
        ForegroundRole = 9,
#if QT_DEPRECATED_SINCE(5, 13) // ### Qt 6: remove me
        BackgroundColorRole Q_DECL_ENUMERATOR_DEPRECATED = BackgroundRole,
        TextColorRole Q_DECL_ENUMERATOR_DEPRECATED = ForegroundRole,
#endif
        CheckStateRole = 10,
        // Accessibility
        AccessibleTextRole = 11,
        AccessibleDescriptionRole = 12,
        // More general purpose
        SizeHintRole = 13,
        InitialSortOrderRole = 14,
        // Internal UiLib roles. Start worrying when public roles go that high.
        DisplayPropertyRole = 27,
        DecorationPropertyRole = 28,
        ToolTipPropertyRole = 29,
        StatusTipPropertyRole = 30,
        WhatsThisPropertyRole = 31,
        // Reserved
        UserRole = 0x0100
    };

    enum ItemFlag {
        NoItemFlags = 0,
        ItemIsSelectable = 1,
        ItemIsEditable = 2,
        ItemIsDragEnabled = 4,
        ItemIsDropEnabled = 8,
        ItemIsUserCheckable = 16,
        ItemIsEnabled = 32,
        ItemIsAutoTristate = 64,
#if QT_DEPRECATED_SINCE(5, 6)
        ItemIsTristate = ItemIsAutoTristate,
#endif
        ItemNeverHasChildren = 128,
        ItemIsUserTristate = 256
    };
    Q_DECLARE_FLAGS(ItemFlags, ItemFlag)
    Q_DECLARE_OPERATORS_FOR_FLAGS(ItemFlags)