qrangemodel_impl.h

Go to the documentation of this file.

// Copyright (C) 2025 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
// Qt-Security score:significant reason:default
 
#ifndef QRANGEMODEL_IMPL_H
#define QRANGEMODEL_IMPL_H
 
#ifndef Q_QDOC
 
#ifndef QRANGEMODEL_H
#error Do not include qrangemodel_impl.h directly
#endif
 
#if 0
#pragma qt_sync_skip_header_check
#pragma qt_sync_stop_processing
#endif
 
#include <QtCore/qabstractitemmodel.h>
#include <QtCore/qcollator.h>
#include <QtCore/qquasivirtual_impl.h>
#include <QtCore/qmetaobject.h>
#include <QtCore/qvariant.h>
#include <QtCore/qmap.h>
#include <QtCore/qscopedvaluerollback.h>
#include <QtCore/qset.h>
#include <QtCore/qregularexpression.h>
#include <QtCore/qvarlengtharray.h>
 
#include <algorithm>
#include <functional>
#include <iterator>
#include <type_traits>
#include <QtCore/qxptype_traits.h>
#include <tuple>
#include <QtCore/q23utility.h>
 
QT_BEGIN_NAMESPACE
 
namespace QRangeModelDetails
{
    template <typename T, template <typename...> typename... Templates>
    struct is_any_of_impl : std::false_type {};
 
    template <template <typename...> typename Template,
              typename... Params,
              template <typename...> typename... Templates>
    struct is_any_of_impl<Template<Params...>, Template, Templates...> : std::true_type {};
 
    template <typename T,
              template <typename...> typename Template,
              template <typename...> typename... Templates>
    struct is_any_of_impl<T, Template, Templates...> : is_any_of_impl<T, Templates...> {};
 
    template <typename T, template <typename...> typename... Templates>
    using is_any_of = is_any_of_impl<std::remove_cv_t<T>, Templates...>;
 
    template <typename T, typename = void>
    struct is_validatable : std::false_type {};
 
    template <typename T>
    struct is_validatable<T, std::void_t<decltype(*std::declval<T>())>>
        : std::is_constructible<bool, T> {};
 
    template <typename T, typename = void>
    struct is_smart_ptr : std::false_type {};
 
    template <typename T>
    struct is_smart_ptr<T,
        std::enable_if_t<std::conjunction_v<
                std::is_pointer<decltype(std::declval<T&>().get())>,
                std::is_same<decltype(*std::declval<T&>().get()), decltype(*std::declval<T&>())>,
                is_validatable<T>
            >>>
        : std::true_type
    {};
 
    // TODO: shouldn't we check is_smart_ptr && !is_copy_constructible && !is_copy_assignable
    //       to support users-specific ptrs?
    template <typename T>
    using is_any_unique_ptr = is_any_of<T,
#ifndef QT_NO_SCOPED_POINTER
            QScopedPointer,
#endif
            std::unique_ptr
        >;
 
    template <typename T>
    using is_any_shared_ptr = is_any_of<T, std::shared_ptr, QSharedPointer,
                                           QExplicitlySharedDataPointer, QSharedDataPointer>;
 
    template <typename T>
    using is_any_owning_ptr = std::disjunction<is_any_shared_ptr<T>, is_any_unique_ptr<T>>;
 
    template <typename T>
    using is_owning_or_raw_pointer = std::disjunction<is_any_owning_ptr<T>, std::is_pointer<T>>;
 
    template <typename T>
    static auto pointerTo(T&& t) {
        using Type = q20::remove_cvref_t<T>;
        if constexpr (is_any_of<Type, std::optional>())
            return t ? std::addressof(*std::forward<T>(t)) : nullptr;
        else if constexpr (std::is_pointer<Type>())
            return t;
        else if constexpr (is_smart_ptr<Type>())
            return t.get();
        else if constexpr (is_any_of<Type, std::reference_wrapper>())
            return std::addressof(t.get());
        else
            return std::addressof(std::forward<T>(t));
    }
 
    template <typename T>
    struct wrapped_helper
    {
        using type = std::remove_pointer_t<decltype(QRangeModelDetails::pointerTo(std::declval<T&>()))>;
    };
    template <>
    struct wrapped_helper<void>
    {
        using type = void;
    };
    template <typename T>
    using wrapped_t = typename QRangeModelDetails::wrapped_helper<T>::type;
 
    template <typename T>
    using is_wrapped = std::negation<std::is_same<
            QRangeModelDetails::wrapped_t<T>, std::remove_reference_t<T>
        >>;
 
    template <typename T, typename = void>
    struct tuple_like : std::false_type {};
    template <typename T, std::size_t N>
    struct tuple_like<std::array<T, N>> : std::false_type {};
    template <typename T>
    struct tuple_like<T, std::void_t<std::tuple_element_t<0, QRangeModelDetails::wrapped_t<T>>>>
        : std::true_type {};
    template <typename T>
    [[maybe_unused]] static constexpr bool tuple_like_v = tuple_like<T>::value;
 
    template <typename T, typename = void>
    struct array_like : std::false_type {};
    template <typename T, std::size_t N>
    struct array_like<std::array<T, N>> : std::true_type {};
    template <typename T, std::size_t N>
    struct array_like<T[N]> : std::true_type {};
    template <typename T>
    [[maybe_unused]] static constexpr bool array_like_v = array_like<T>::value;
 
    template <typename T, typename = void>
    struct has_metaobject : std::false_type {};
    template <typename T>
    struct has_metaobject<T, std::void_t<decltype(QRangeModelDetails::wrapped_t<T>::staticMetaObject)>>
        : std::true_type {};
    template <typename T>
    [[maybe_unused]] static constexpr bool has_metaobject_v = has_metaobject<T>::value;
 
    template <typename T>
    static constexpr bool isValid(const T &t) noexcept
    {
        if constexpr (std::is_array_v<T>)
            return true;
        else if constexpr (is_validatable<T>())
            return bool(t);
        else
            return true;
    }
 
    template <typename T>
    static decltype(auto) refTo(T&& t) {
        Q_ASSERT(QRangeModelDetails::isValid(t));
        // it's allowed to move only if the object holds unique ownership of the wrapped data
        using Type = q20::remove_cvref_t<T>;
        if constexpr (is_any_of<T, std::optional>())
            return *std::forward<T>(t); // let std::optional resolve dereferencing
        if constexpr (!is_wrapped<Type>() || is_any_unique_ptr<Type>())
            return q23::forward_like<T>(*QRangeModelDetails::pointerTo(t));
        else
            return *QRangeModelDetails::pointerTo(t);
    }
 
    template <typename It>
    auto key(It&& it) -> decltype(it.key()) { return std::forward<It>(it).key(); }
    template <typename It>
    auto key(It&& it) -> decltype((it->first)) { return std::forward<It>(it)->first; }
 
    template <typename It>
    auto value(It&& it) -> decltype(it.value()) { return std::forward<It>(it).value(); }
    template <typename It>
    auto value(It&& it) -> decltype((it->second)) { return std::forward<It>(it)->second; }
 
    // use our own, ADL friendly versions of begin/end so that we can overload
    // for pointers.
    using std::begin;
    using std::end;
    template <typename C>
    static auto adl_begin(C &&c) -> decltype(begin(QRangeModelDetails::refTo(std::forward<C>(c))))
    { return begin(QRangeModelDetails::refTo(std::forward<C>(c))); }
    template <typename C>
    static auto adl_end(C &&c) -> decltype(end(QRangeModelDetails::refTo(std::forward<C>(c))))
    { return end(QRangeModelDetails::refTo(std::forward<C>(c))); }
    template <typename C>
    static auto pos(C &&c, int i)
    { return std::next(QRangeModelDetails::adl_begin(std::forward<C>(c)), i); }
 
    // Test if a type is a range, and whether we can modify it using the
    // standard C++ container member functions insert, erase, and resize.
    // For the sake of QAIM, we cannot modify a range if it holds const data
    // even if the range itself is not const; we'd need to initialize new rows
    // and columns, and move old row and column data.
    template <typename C, typename = void>
    struct test_insert : std::false_type {};
 
    template <typename C>
    struct test_insert<C, std::void_t<decltype(std::declval<C>().insert(
        std::declval<typename C::const_iterator>(),
        std::declval<typename C::size_type>(),
        std::declval<typename C::value_type>()
    ))>>
        : std::true_type
    {};
 
    // Can we insert from another (identical) range? Required to support
    // move-only types
    template <typename C, typename = void>
    struct test_insert_range : std::false_type {};
 
    template <typename C>
    struct test_insert_range<C, std::void_t<decltype(std::declval<C&>().insert(
      std::declval<typename C::const_iterator&>(),
      std::declval<std::move_iterator<typename C::iterator>&>(),
      std::declval<std::move_iterator<typename C::iterator>&>()
    ))>>
        : std::true_type
    {};
 
    template <typename C, typename = void>
    struct test_erase : std::false_type {};
 
    template <typename C>
    struct test_erase<C, std::void_t<decltype(std::declval<C>().erase(
        std::declval<typename C::const_iterator>(),
        std::declval<typename C::const_iterator>()
    ))>>
        : std::true_type
    {};
 
    template <typename C, typename = void>
    struct test_resize : std::false_type {};
 
    template <typename C>
    struct test_resize<C, std::void_t<decltype(std::declval<C>().resize(
        std::declval<typename C::size_type>(),
        std::declval<typename C::value_type>()
    ))>>
        : std::true_type
    {};
 
    // we use std::rotate in moveRows/Columns, which requires the values (which
    // might be const if we only get a const iterator) to be swappable, and the
    // iterator type to be at least a forward iterator
    template <typename It>
    using test_rotate = std::conjunction<
                            std::is_swappable<decltype(*std::declval<It>())>,
                            std::is_base_of<std::forward_iterator_tag,
                                            typename std::iterator_traits<It>::iterator_category>
                        >;
 
    template <typename C, typename = void>
    struct test_splice : std::false_type {};
 
    template <typename C>
    struct test_splice<C, std::void_t<decltype(std::declval<C>().splice(
        std::declval<typename C::const_iterator>(),
        std::declval<C&>(),
        std::declval<typename C::const_iterator>(),
        std::declval<typename C::const_iterator>()
    ))>>
        : std::true_type
    {};
 
    template <typename C>
    static void rotate(C& c, int src, int count, int dst) {
        auto& container = QRangeModelDetails::refTo(c);
        using Container = std::remove_reference_t<decltype(container)>;
 
        const auto srcBegin = QRangeModelDetails::pos(container, src);
        const auto srcEnd = std::next(srcBegin, count);
        const auto dstBegin = QRangeModelDetails::pos(container, dst);
 
        if constexpr (test_splice<Container>::value) {
            if (dst > src && dst < src + count) // dst must be out of the source range
                container.splice(srcBegin, container, dstBegin, srcEnd);
            else if (dst != src) // otherwise, std::list gets corrupted
                container.splice(dstBegin, container, srcBegin, srcEnd);
        } else {
            if (src < dst) // moving right
                std::rotate(srcBegin, srcEnd, dstBegin);
            else // moving left
                std::rotate(dstBegin, srcBegin, srcEnd);
        }
    }
 
    // Test if a type is an associative container that we can use for multi-role
    // data, i.e. has a key_type and a mapped_type typedef, and maps from int,
    // Qt::ItemDataRole, or QString to QVariant. This excludes std::set (and
    // unordered_set), which are not useful for us anyway even though they are
    // considered associative containers.
    template <typename C, typename = void> struct is_multi_role : std::false_type
    {
        static constexpr bool int_key = false;
    };
    template <typename C> // Qt::ItemDataRole -> QVariant, or QString -> QVariant, int -> QVariant
    struct is_multi_role<C, std::void_t<typename C::key_type, typename C::mapped_type>>
        : std::conjunction<std::disjunction<std::is_same<typename C::key_type, int>,
                                            std::is_same<typename C::key_type, Qt::ItemDataRole>,
                                            std::is_same<typename C::key_type, QString>>,
                           std::is_same<typename C::mapped_type, QVariant>>
    {
        static constexpr bool int_key = !std::is_same_v<typename C::key_type, QString>;
    };
    template <typename C>
    [[maybe_unused]]
    static constexpr bool is_multi_role_v = is_multi_role<C>::value;
 
    using std::size;
    template <typename C, typename = void>
    struct test_size : std::false_type {};
    template <typename C>
    struct test_size<C, std::void_t<decltype(size(std::declval<C&>()))>> : std::true_type {};
 
    template <typename C, typename = void>
    struct test_cbegin : std::false_type {};
    template <typename C>
    struct test_cbegin<C, std::void_t<decltype(QRangeModelDetails::adl_begin(std::declval<const C&>()))>>
        : std::true_type
    {};
 
    template <typename C, typename = void>
    struct range_traits : std::false_type {
        static constexpr bool is_mutable = !std::is_const_v<C>;
        static constexpr bool has_insert = false;
        static constexpr bool has_insert_range = false;
        static constexpr bool has_erase = false;
        static constexpr bool has_resize = false;
        static constexpr bool has_rotate = false;
        static constexpr bool has_splice = false;
        static constexpr bool has_cbegin = false;
    };
    template <typename C>
    struct range_traits<C, std::void_t<decltype(QRangeModelDetails::adl_begin(std::declval<C&>())),
                                       decltype(QRangeModelDetails::adl_end(std::declval<C&>())),
                                       std::enable_if_t<!QRangeModelDetails::is_multi_role_v<C>>
                                      >> : std::true_type
    {
        using iterator = decltype(QRangeModelDetails::adl_begin(std::declval<C&>()));
        using value_type = std::remove_reference_t<decltype(*std::declval<iterator&>())>;
        static constexpr bool is_mutable = !std::is_const_v<C> && !std::is_const_v<value_type>;
        static constexpr bool has_insert = test_insert<C>();
        static constexpr bool has_insert_range = test_insert_range<C>();
        static constexpr bool has_erase = test_erase<C>();
        static constexpr bool has_resize = test_resize<C>();
        static constexpr bool has_rotate = test_rotate<iterator>();
        static constexpr bool has_splice = test_splice<C>();
        static constexpr bool has_cbegin = test_cbegin<C>::value;
    };
 
    // Specializations for types that look like ranges, but should be
    // treated as values.
    enum class Mutable { Yes, No };
    template <Mutable IsMutable>
    struct iterable_value : std::false_type {
        static constexpr bool is_mutable = IsMutable == Mutable::Yes;
        static constexpr bool has_insert = false;
        static constexpr bool has_erase = false;
        static constexpr bool has_resize = false;
        static constexpr bool has_rotate = false;
        static constexpr bool has_splice = false;
        static constexpr bool has_cbegin = true;
    };
    template <> struct range_traits<QByteArray> : iterable_value<Mutable::Yes> {};
    template <> struct range_traits<QString> : iterable_value<Mutable::Yes> {};
    template <class CharT, class Traits, class Allocator>
    struct range_traits<std::basic_string<CharT, Traits, Allocator>> : iterable_value<Mutable::Yes>
    {};
 
    // const T * and views are read-only
    template <typename T> struct range_traits<const T *> : iterable_value<Mutable::No> {};
    template <> struct range_traits<QLatin1StringView> : iterable_value<Mutable::No> {};
 
    template <typename C>
    using is_range = range_traits<C>;
    template <typename C>
    [[maybe_unused]] static constexpr bool is_range_v = is_range<C>();
 
    // Detect an ItemAccess specialization with static read/writeRole members
    template <typename T> struct QRangeModelItemAccess;
 
    template <typename T>
    struct item_access
    {
        using ItemType = std::remove_pointer_t<T>;
        using ItemAccess = QRangeModelItemAccess<ItemType>;
 
        template <typename Access, typename Test>
        using hasReadRole_test = decltype(Access::readRole(std::declval<const Test &>(),
                                                           Qt::DisplayRole));
        static constexpr bool hasReadRole = qxp::is_detected_v<hasReadRole_test, ItemAccess, ItemType>;
 
        template <typename Access, typename Test>
        using hasWriteRole_test = decltype(Access::writeRole(std::declval<Test&>(),
                                                             std::declval<QVariant>(), Qt::DisplayRole));
        static constexpr bool hasWriteRole = qxp::is_detected_v<hasWriteRole_test, ItemAccess, ItemType>;
 
        template <typename Access, typename Test>
        using hasFlags_test = decltype(Access::flags(std::declval<const Test&>()));
 
        static constexpr bool hasFlags = qxp::is_detected_v<hasFlags_test, ItemAccess, ItemType>;
 
        template <typename Access, typename Test>
        using hasMimeTypes_test = decltype(Access::mimeTypes());
        static constexpr bool hasMimeTypes = qxp::is_detected_v<hasMimeTypes_test, ItemAccess, ItemType>;
 
        template <typename Access, typename Test>
        using hasMimeData_test = decltype(Access::mimeData(std::declval<QSpan<const Test>>()));
        static constexpr bool hasMimeData = qxp::is_detected_v<hasMimeData_test, ItemAccess, ItemType>;
 
        template <typename Access>
        using hasCanDropMimeData_test = decltype(Access::canDropMimeData(
            std::declval<const QMimeData *>()
        ));
        static constexpr bool hasCanDropMimeData = qxp::is_detected_v<hasCanDropMimeData_test, ItemAccess>;
        template <typename Access, typename Test>
        using hasDropMimeData_test = decltype(Access::dropMimeData(
            std::declval<const QMimeData *>(),
            std::declval<std::back_insert_iterator<std::vector<Test>>>())
        );
        static constexpr bool hasDropMimeData = qxp::is_detected_v<hasDropMimeData_test,
                                                                   ItemAccess, ItemType>;
 
        // full versions with all parameters
        template <typename Access>
        using hasCanDropMimeDataFull_test = decltype(Access::canDropMimeData(
            std::declval<const QMimeData *>(), Qt::CopyAction, 0, 0, std::declval<const QModelIndex &>()
        ));
        static constexpr bool hasCanDropMimeDataFull = qxp::is_detected_v<hasCanDropMimeDataFull_test,
                                                                          ItemAccess>;
        template <typename Access, typename Test>
        using hasDropMimeDataFull_test = decltype(Access::dropMimeData(
            std::declval<const QMimeData *>(),
            Qt::CopyAction, 0, 0, std::declval<const QModelIndex &>(),
            std::declval<std::back_insert_iterator<std::vector<Test>>>()
        ));
        static constexpr bool hasDropMimeDataFull = qxp::is_detected_v<hasDropMimeDataFull_test,
                                                                       ItemAccess, ItemType>;
    };
 
    // Detect which options are set to override default heuristics. Since
    // QRangeModel is not yet defined we need to delay the evaluation.
    template <typename T> struct QRangeModelRowOptions;
 
    template <typename T, typename = void>
    struct row_category : std::false_type
    {
        static constexpr bool isMultiRole = item_access<std::remove_pointer_t<T>>::hasReadRole;
    };
 
    template <typename T>
    struct row_category<T, std::void_t<decltype(QRangeModelRowOptions<T>::rowCategory)>>
        : std::true_type
    {
        static constexpr auto rowCategory = QRangeModelRowOptions<T>::rowCategory;
        using RowCategory = decltype(rowCategory);
        static constexpr bool isMultiRole = rowCategory == RowCategory::MultiRoleItem;
    };
 
    template <typename RowOptions>
    using hasHeaderData_test = decltype(RowOptions::headerData(0, Qt::DisplayRole));
    template <typename row_type>
    static constexpr bool hasHeaderData = qxp::is_detected_v<hasHeaderData_test, QRangeModelRowOptions<row_type>>;
 
    template <typename row_type>
    using hasRowFlags_test = decltype(QRangeModelRowOptions<row_type>::flags(std::declval<const row_type &>()));
    template <typename row_type>
    static constexpr bool hasRowFlags = qxp::is_detected_v<hasRowFlags_test, row_type>;
 
    // drag'n'drop handling
    template <typename row_type>
    using hasMimeTypes_test = decltype(QRangeModelRowOptions<row_type>::mimeTypes());
    template <typename row_type>
    static constexpr bool hasMimeTypes = qxp::is_detected_v<hasMimeTypes_test, row_type>;
    template <typename row_type>
    using hasMimeDataIndexList_test = decltype(QRangeModelRowOptions<row_type>::mimeData(
        std::declval<const QModelIndexList &>())
    );
    template <typename row_type>
    static constexpr bool hasMimeDataIndexList = qxp::is_detected_v<hasMimeDataIndexList_test, row_type>;
    template <typename row_type>
    using hasMimeDataRowSpan_test = decltype(QRangeModelRowOptions<row_type>::mimeData(
        // we don't call it with a QSpan, but with a range type. QSpan is a close enough match.
        std::declval<QSpan<const row_type>>())
    );
    template <typename row_type>
    static constexpr bool hasMimeDataRowSpan = qxp::is_detected_v<hasMimeDataRowSpan_test, row_type>;
 
    // we allow simplified versions of (can)DropMimeData
    template <typename row_type>
    using hasCanDropMimeData_test = decltype(QRangeModelRowOptions<row_type>::canDropMimeData(
        std::declval<const QMimeData *>()
    ));
    template <typename row_type>
    static constexpr bool hasCanDropMimeData = qxp::is_detected_v<hasCanDropMimeData_test, row_type>;
    template <typename row_type>
    using hasDropMimeData_test = decltype(QRangeModelRowOptions<row_type>::dropMimeData(
        std::declval<const QMimeData *>(),
        std::declval<std::back_insert_iterator<std::vector<row_type>>>()
    ));
    template <typename row_type>
    static constexpr bool hasDropMimeData = qxp::is_detected_v<hasDropMimeData_test, row_type>;
 
    // the full versions get all the parameters
    template <typename row_type>
    using hasCanDropMimeDataFull_test = decltype(QRangeModelRowOptions<row_type>::canDropMimeData(
        std::declval<const QMimeData *>(), Qt::CopyAction, 0, 0, std::declval<const QModelIndex &>()
    ));
    template <typename row_type>
    static constexpr bool hasCanDropMimeDataFull = qxp::is_detected_v<hasCanDropMimeDataFull_test,
                                                                      row_type>;
    template <typename row_type>
    using hasDropMimeDataFull_test = decltype(QRangeModelRowOptions<row_type>::dropMimeData(
        std::declval<const QMimeData *>(),
        Qt::CopyAction, 0, 0, std::declval<const QModelIndex &>(),
        std::declval<std::back_insert_iterator<std::vector<row_type>>>()
    ));
    template <typename row_type>
    static constexpr bool hasDropMimeDataFull = qxp::is_detected_v<hasDropMimeDataFull_test,
                                                                   row_type>;
 
    // Find out how many fixed elements can be retrieved from a row element.
    // main template for simple values and ranges. Specializing for ranges
    // is ambiguous with arrays, as they are also ranges
    template <typename T, typename = void>
    struct row_traits {
        static constexpr bool is_range = is_range_v<q20::remove_cvref_t<T>>
                                      && !row_category<T>::isMultiRole;
        // A static size of -1 indicates dynamically sized range
        // A static size of 0 indicates that the specified type doesn't
        // represent static or dynamic range.
        static constexpr int static_size = is_range ? -1 : 0;
        using item_type = std::conditional_t<is_range, typename range_traits<T>::value_type, T>;
        static constexpr int fixed_size() { return 1; }
        static constexpr bool hasMetaObject = false;
 
        static QVariant column_name(int)
        {
            return {};
        }
 
        template <typename C, typename Fn>
        static bool for_element_at(C &&container, std::size_t idx, Fn &&fn)
        {
            if constexpr (is_range)
                return std::forward<Fn>(fn)(*QRangeModelDetails::pos(std::forward<C>(container), idx));
            else
                return std::forward<Fn>(fn)(std::forward<C>(container));
        }
 
        template <typename Fn>
        static bool for_each_element(const T &row, const QModelIndex &firstIndex, Fn &&fn)
        {
            if constexpr (static_size == 0) {
                return std::forward<Fn>(fn)(firstIndex, QRangeModelDetails::pointerTo(row));
            } else {
                int columnIndex = -1;
                return std::all_of(QRangeModelDetails::adl_begin(row),
                                   QRangeModelDetails::adl_end(row), [&](const auto &item) {
                    return std::forward<Fn>(fn)(firstIndex.siblingAtColumn(++columnIndex),
                                                QRangeModelDetails::pointerTo(item));
                });
            }
        }
    };
 
    // Specialization for tuple-like semantics (prioritized over metaobject)
    template <typename T>
    struct row_traits<T, std::enable_if_t<tuple_like_v<T> && !row_category<T>::isMultiRole>>
    {
        static constexpr std::size_t size64 = std::tuple_size_v<T>;
        static_assert(q20::in_range<int>(size64));
        static constexpr int static_size = int(size64);
 
        // are the types in a tuple all the same
        template <std::size_t ...I>
        static constexpr bool allSameTypes(std::index_sequence<I...>)
        {
            return (std::is_same_v<std::tuple_element_t<0, T>,
                                   std::tuple_element_t<I, T>> && ...);
        }
 
        using item_type = std::conditional_t<allSameTypes(std::make_index_sequence<size64>{}),
                                             std::tuple_element_t<0, T>, void>;
        static constexpr int fixed_size() { return 0; }
        static constexpr bool hasMetaObject = false;
 
        template <typename C, typename F>
        static auto for_element_at(C &&container, std::size_t idx, F &&function)
        {
            using type = q20::remove_cvref_t<QRangeModelDetails::wrapped_t<C>>;
            constexpr size_t size = std::tuple_size_v<type>;
            Q_ASSERT(idx < size);
            return QtPrivate::applyIndexSwitch<size>(idx, [&](auto idxConstant) {
                return function(get<idxConstant>(QRangeModelDetails::refTo(std::forward<C>(container))));
            });
        }
 
        static QVariant column_name(int section)
        {
            constexpr auto size = std::tuple_size_v<T>;
            Q_ASSERT(std::size_t(section) < size);
 
            QVariant result;
            QtPrivate::applyIndexSwitch<size>(section, [&result](auto idxConstant) {
                using ElementType = std::tuple_element_t<idxConstant.value, T>;
                const QMetaType metaType = QMetaType::fromType<
                                                QRangeModelDetails::wrapped_t<ElementType>
                                           >();
                if (metaType.isValid())
                    result = QString::fromUtf8(metaType.name());
            });
            return result;
        }
 
        template <typename Fn, std::size_t ...Is>
        static bool forEachTupleElement(const T &row, Fn &&fn, std::index_sequence<Is...>)
        {
            using std::get;
            return (std::forward<Fn>(fn)(QRangeModelDetails::pointerTo(get<Is>(row))) && ...);
        }
 
        template <typename Fn>
        static bool for_each_element(const T &row, const QModelIndex &firstIndex, Fn &&fn)
        {
            int column = -1;
            return forEachTupleElement(row, [&column, &fn, &firstIndex](const QObject *item){
                return std::forward<Fn>(fn)(firstIndex.siblingAtColumn(++column), item);
            }, std::make_index_sequence<static_size>());
        }
    };
 
    // Specialization for C arrays and std::array
    template <typename T, std::size_t N>
    struct row_traits<std::array<T, N>>
    {
        static_assert(q20::in_range<int>(N));
        static constexpr int static_size = int(N);
        using item_type = T;
        static constexpr int fixed_size() { return 0; }
        static constexpr bool hasMetaObject = false;
 
        template <typename C, typename F>
        static auto for_element_at(C &&container, std::size_t idx, F &&function)
        {
            Q_ASSERT(idx < size(QRangeModelDetails::refTo(std::forward<C>(container))));
            return function(QRangeModelDetails::refTo(std::forward<C>(container))[idx]);
        }
 
        static QVariant column_name(int section)
        {
            return section;
        }
 
        template <typename Fn>
        static bool for_each_element(const std::array<T, N> &row, const QModelIndex &firstIndex, Fn &&fn)
        {
            int columnIndex = -1;
            return std::all_of(QRangeModelDetails::adl_begin(row),
                               QRangeModelDetails::adl_end(row), [&](const auto &item) {
                return std::forward<Fn>(fn)(firstIndex.siblingAtColumn(++columnIndex),
                                            QRangeModelDetails::pointerTo(item));
            });
        }
    };
 
    template <typename T, std::size_t N>
    struct row_traits<T[N]> : row_traits<std::array<T, N>> {};
 
    // prioritize tuple-like over metaobject
    template <typename T>
    struct row_traits<T, std::enable_if_t<has_metaobject_v<T> && !tuple_like_v<T>>>
    {
        static constexpr int static_size = 0;
        using item_type = std::conditional_t<row_category<T>::isMultiRole, T, void>;
        static int fixed_size() {
            if constexpr (row_category<T>::isMultiRole) {
                return 1;
            } else {
                // Interpret a gadget in a list as a multi-column row item. To make
                // a list of multi-role items, wrap it into SingleColumn.
                static const int columnCount = []{
                    const QMetaObject &mo = T::staticMetaObject;
                    return mo.propertyCount() - mo.propertyOffset();
                }();
                return columnCount;
            }
        }
 
        static constexpr bool hasMetaObject = true;
 
        template <typename C, typename F>
        static auto for_element_at(C &&container, std::size_t, F &&function)
        {
            return std::forward<F>(function)(std::forward<C>(container));
        }
 
        static QVariant column_name(int section)
        {
            QVariant result;
            if (fixed_size() == 1) {
                const QMetaType metaType = QMetaType::fromType<T>();
                result = QString::fromUtf8(metaType.name());
            } else if (section <= fixed_size()) {
                const QMetaProperty prop = T::staticMetaObject.property(
                                    section + T::staticMetaObject.propertyOffset());
                result = QString::fromUtf8(prop.name());
            }
            return result;
        }
 
        template <typename Fn>
        static bool for_each_element(const T &row, const QModelIndex &firstIndex, Fn &&fn)
        {
            return std::forward<Fn>(fn)(firstIndex, QRangeModelDetails::pointerTo(row));
        }
    };
 
    template <typename T, typename = void>
    struct item_traits
    {
        template <typename That>
        static QHash<int, QByteArray> roleNames(That *)
        {
            return That::roleNamesForSimpleType();
        }
    };
 
    template <>
    struct item_traits<void>
    {
        template <typename That>
        static QHash<int, QByteArray> roleNames(That *that)
        {
            return that->itemModel().QAbstractItemModel::roleNames();
        }
    };
 
    template <typename T>
    struct item_traits<T, std::enable_if_t<QRangeModelDetails::is_multi_role<T>::value>>
        : item_traits<void>
    {
    };
 
    template <typename T>
    struct item_traits<T, std::enable_if_t<QRangeModelDetails::has_metaobject_v<T>>>
    {
        template <typename That>
        static QHash<int, QByteArray> roleNames(That *that)
        {
            return That::roleNamesForMetaObject(that->itemModel(), T::staticMetaObject);
        }
    };
 
    template <typename T>
    [[maybe_unused]] static constexpr int static_size_v =
            row_traits<std::remove_cv_t<QRangeModelDetails::wrapped_t<T>>>::static_size;
 
    template <typename Range>
    struct ListProtocol
    {
        using row_type = typename range_traits<QRangeModelDetails::wrapped_t<Range>>::value_type;
 
        template <typename R = row_type>
        auto newRow() -> decltype(R{}) { return R{}; }
    };
 
    template <typename Range>
    struct TableProtocol
    {
        using row_type = typename range_traits<QRangeModelDetails::wrapped_t<Range>>::value_type;
 
        template <typename R = row_type,
                  std::enable_if_t<
                      std::conjunction_v<
                          std::is_destructible<QRangeModelDetails::wrapped_t<R>>,
                          is_owning_or_raw_pointer<R>
                      >,
                  bool> = true>
        auto newRow() -> decltype(R(new QRangeModelDetails::wrapped_t<R>)) {
            if constexpr (is_any_of<R, std::shared_ptr>())
                return std::make_shared<QRangeModelDetails::wrapped_t<R>>();
            else
                return R(new QRangeModelDetails::wrapped_t<R>);
        }
 
        template <typename R = row_type,
                  std::enable_if_t<!is_owning_or_raw_pointer<R>::value, bool> = true>
        auto newRow() -> decltype(R{}) { return R{}; }
 
        template <typename R = row_type,
                  std::enable_if_t<std::is_pointer_v<std::remove_reference_t<R>>, bool> = true>
        auto deleteRow(R&& row) -> decltype(delete row) { delete row; }
    };
 
    template <typename Range,
              typename R = typename range_traits<QRangeModelDetails::wrapped_t<Range>>::value_type>
    using table_protocol_t = std::conditional_t<static_size_v<R> == 0 && !has_metaobject_v<R>,
                                                ListProtocol<Range>, TableProtocol<Range>>;
 
    // Default tree traversal protocol implementation for row types that have
    // the respective member functions. The trailing return type implicitly
    // removes those functions that are not available.
    template <typename Range>
    struct DefaultTreeProtocol : TableProtocol<Range>
    {
        template <typename R /*wrapped_row_type*/>
        auto parentRow(const R& row) const -> decltype(row.parentRow())
        {
            return row.parentRow();
        }
 
        template <typename R /* = wrapped_row_type*/>
        auto setParentRow(R &row, R* parent) -> decltype(row.setParentRow(parent))
        {
            row.setParentRow(parent);
        }
 
        template <typename R /* = wrapped_row_type*/>
        auto childRows(const R &row) const -> decltype(row.childRows())
        {
            return row.childRows();
        }
 
        template <typename R /* = wrapped_row_type*/>
        auto childRows(R &row) -> decltype(row.childRows())
        {
            return row.childRows();
        }
    };
 
    template <typename P, typename R>
    using protocol_parentRow_test = decltype(std::declval<P&>()
            .parentRow(std::declval<QRangeModelDetails::wrapped_t<R>&>()));
    template <typename P, typename R>
    using protocol_parentRow = qxp::is_detected<protocol_parentRow_test, P, R>;
 
    template <typename P, typename R>
    using protocol_childRows_test = decltype(std::declval<P&>()
            .childRows(std::declval<QRangeModelDetails::wrapped_t<R>&>()));
    template <typename P, typename R>
    using protocol_childRows = qxp::is_detected<protocol_childRows_test, P, R>;
 
    template <typename P, typename R>
    using protocol_setParentRow_test = decltype(std::declval<P&>()
            .setParentRow(std::declval<QRangeModelDetails::wrapped_t<R>&>(),
                          std::declval<QRangeModelDetails::wrapped_t<R>*>()));
    template <typename P, typename R>
    using protocol_setParentRow = qxp::is_detected<protocol_setParentRow_test, P, R>;
 
    template <typename P, typename R>
    using protocol_mutable_childRows_test = decltype(QRangeModelDetails::refTo(std::declval<P&>()
            .childRows(std::declval<QRangeModelDetails::wrapped_t<R>&>())) = {});
    template <typename P, typename R>
    using protocol_mutable_childRows = qxp::is_detected<protocol_mutable_childRows_test, P, R>;
 
    template <typename P, typename = void>
    struct protocol_newRow : std::false_type {};
    template <typename P>
    struct protocol_newRow<P, std::void_t<decltype(std::declval<P&>().newRow())>>
        : std::true_type {};
 
    template <typename P, typename R, typename = void>
    struct protocol_deleteRow : std::false_type {};
    template <typename P, typename R>
    struct protocol_deleteRow<P, R,
            std::void_t<decltype(std::declval<P&>().deleteRow(std::declval<R&&>()))>>
        : std::true_type {};
 
    template <typename Range,
              typename Protocol = DefaultTreeProtocol<Range>,
              typename R = typename range_traits<Range>::value_type,
              typename = void>
    struct is_tree_range : std::false_type {};
 
    template <typename Range, typename Protocol, typename R>
    struct is_tree_range<Range, Protocol, R,
                         std::enable_if_t<std::conjunction_v<
                            protocol_parentRow<Protocol, R>, protocol_childRows<Protocol, R>>>
            > : std::true_type {};
 
    template <typename Range>
    using if_table_range = std::enable_if_t<std::conjunction_v<
            is_range<QRangeModelDetails::wrapped_t<Range>>,
            std::negation<is_tree_range<QRangeModelDetails::wrapped_t<Range>>>
        >, bool>;
 
    template <typename Range, typename Protocol = DefaultTreeProtocol<Range>>
    using if_tree_range = std::enable_if_t<std::conjunction_v<
            is_range<QRangeModelDetails::wrapped_t<Range>>,
            is_tree_range<QRangeModelDetails::wrapped_t<Range>,
                          QRangeModelDetails::wrapped_t<Protocol>>
        >, bool>;
 
    template <typename Range, typename Protocol>
    struct protocol_traits
    {
        using protocol = QRangeModelDetails::wrapped_t<Protocol>;
        using row = typename range_traits<QRangeModelDetails::wrapped_t<Range>>::value_type;
        static constexpr bool is_tree = std::conjunction_v<protocol_parentRow<protocol, row>,
                                                           protocol_childRows<protocol, row>>;
        static constexpr bool is_list = static_size_v<row> == 0
                                     && (!has_metaobject_v<row> || row_category<row>::isMultiRole);
        static constexpr bool is_table = !is_list && !is_tree;
 
        static constexpr bool has_newRow = protocol_newRow<protocol>();
        static constexpr bool has_deleteRow = protocol_deleteRow<protocol, row>();
        static constexpr bool has_setParentRow = protocol_setParentRow<protocol, row>();
        static constexpr bool has_mutable_childRows = protocol_mutable_childRows<protocol, row>();
 
        static constexpr bool is_default = is_any_of<protocol, ListProtocol, TableProtocol, DefaultTreeProtocol>();
    };
 
    // Helpers for drag'n'drop:
    // MimeDataEntry gives customisations access to a pair of either a row or
    // an item (in form of the underlying type, i.e. unwrapped, as that's what
    // customizations specialize RowOptions and ItemAccess for), and the
    // corresponding index, with decomposition support for easy iteration.
    template <typename Entry>
    struct MimeDataEntry
    {
        using entry_type = q20::remove_cvref_t<Entry>;
        using wrapped_entry = QRangeModelDetails::wrapped_t<entry_type>;
        template<typename T, typename = void>
        struct is_constexpr_default_constructible : std::false_type {};
 
#ifndef Q_CC_MSVC // MSVC selects this even for non-constexpr types
        template<typename T>
        struct is_constexpr_default_constructible<T, std::void_t<int(*)[(T(), 1)]>> : std::true_type {};
#endif
 
        bool isValid() const { return QRangeModelDetails::isValid(m_entry); }
        const wrapped_entry &entry() const
        {
            if constexpr (QRangeModelDetails::is_owning_or_raw_pointer<entry_type>()) {
                // While we mark null-items or indexes in null-rows as not draggable,
                // client code might override that, or explicitly call QRM::mimeData()
                // with indexes that point at null-rows or -items.
                if (Q_UNLIKELY(!QRangeModelDetails::isValid(m_entry))) {
#ifndef QT_NO_DEBUG
                    qDebug("QRangeModel::mimeData: null-entry, test with isValid before accessing");
#endif
                    constexpr bool is_constexpr_default_constructible_v =
                                        is_constexpr_default_constructible<wrapped_entry>::value;
                    if constexpr (is_constexpr_default_constructible_v) {
                        Q_CONSTINIT static const wrapped_entry emptyDefault;
                        return QRangeModelDetails::refTo(emptyDefault);
                    } else {
                        // known to cause runtime initialization
                        static const wrapped_entry emptyDefault;
                        return QRangeModelDetails::refTo(emptyDefault);
                    }
                }
            }
            return std::as_const(QRangeModelDetails::refTo(m_entry));
        }
 
        const QModelIndex &index() const { return m_index; }
 
        template <std::size_t N>
        friend decltype(auto) get(const MimeDataEntry &entry)
        {
            if constexpr (N == 0)
                return entry.entry();
            else if constexpr (N == 1)
                return entry.index();
        }
        const Entry &m_entry;
        const QModelIndex m_index;
    };
} // namespace QRangeModelDetails
 
QT_END_NAMESPACE
 
// decomposition protocol
namespace std {
template <typename T>
struct tuple_size<QT_PREPEND_NAMESPACE(QRangeModelDetails::MimeDataEntry<T>)>
    : std::integral_constant<std::size_t, 2> {};
template <typename T>
struct tuple_element<0, QT_PREPEND_NAMESPACE(QRangeModelDetails::MimeDataEntry<T>)>
{ using type = QT_PREPEND_NAMESPACE(QRangeModelDetails)::wrapped_t<T>; };
template <typename T>
struct tuple_element<1, QT_PREPEND_NAMESPACE(QRangeModelDetails::MimeDataEntry<T>)>
{ using type = QT_PREPEND_NAMESPACE(QModelIndex); };
}  // namespace QRangeModelDetails
 
QT_BEGIN_NAMESPACE
 
namespace QRangeModelDetails {
    // A helper type for drop-support. Client code populates a sequence of
    // dropped things via an insertion iterator, and those get wrapped in a
    // DroppedEntry, which allows user code to also specify the position of the
    // thing in the target model.
    template <typename Entry>
    struct DroppedEntry
    {
        struct Cell {
            int m_row;
            int m_column;
 
            // implicit conversion is intentional
            Q_IMPLICIT Cell() noexcept : m_row(-1), m_column(-1)  {}
            Q_IMPLICIT Cell(int row, int column = 0) noexcept : m_row(row), m_column(column) {}
 
            friend bool operator==(const Cell &lhs, const Cell &rhs) noexcept
            {
                return lhs.m_row == rhs.m_row && lhs.m_column == rhs.m_column;
            }
        };
 
        // implicit conversion from and to entry is intentional
        Q_IMPLICIT DroppedEntry(Entry &&entry)
            : m_entry(std::move(entry)), m_cell{-1, -1}
        {}
        Q_IMPLICIT DroppedEntry(Entry &&entry, Cell cell)
            : m_entry(std::move(entry)), m_cell(cell)
        {}
 
        // we only move the actual data out
        operator Entry&&() && { return std::move(m_entry); }
 
        Entry m_entry;
        Cell m_cell;
    };
 
    class Q_CORE_EXPORT AutoConnectContext : public QObject
    {
        Q_DISABLE_COPY_MOVE(AutoConnectContext)
    public:
        enum class AutoConnectMapping
        {
            Roles,
            Columns,
        };
        AutoConnectContext(QObject *parent)
            : QObject(parent)
        {}
        ~AutoConnectContext() override;
 
        AutoConnectMapping mapping = AutoConnectMapping::Roles;
    };
 
    template <bool cacheProperties, bool itemsAreQObjects>
    struct PropertyData {
        static constexpr bool cachesProperties = false;
 
        void invalidateCaches() {}
    };
 
    struct PropertyCache
    {
        static constexpr bool cachesProperties = true;
        mutable QHash<int, QMetaProperty> properties;
 
        void invalidateCaches()
        {
            properties.clear();
        }
    protected:
        ~PropertyCache() = default;
    };
 
    template <>
    struct PropertyData<true, false> : PropertyCache
    {};
 
    struct ConnectionStorage
    {
        struct Connection {
            const QObject *sender;
            int role;
 
            friend bool operator==(const Connection &lhs, const Connection &rhs) noexcept
            {
                return lhs.sender == rhs.sender && lhs.role == rhs.role;
            }
            friend size_t qHash(const Connection &c, size_t seed) noexcept
            {
                return qHashMulti(seed, c.sender, c.role);
            }
        };
 
        AutoConnectContext *context = nullptr;
        mutable QSet<Connection> connections;
 
    protected:
        ~ConnectionStorage() = default;
    };
 
    template <>
    struct PropertyData<true, true> : PropertyCache, ConnectionStorage
    {};
 
    template <>
    struct PropertyData<false, true> : PropertyData<false, false>, ConnectionStorage
    {
        mutable QHash<int, QMetaProperty> properties;
    };
 
    // The storage of the model data. We might store it as a pointer, or as a
    // (copied- or moved-into) value (or smart pointer). But we always return a
    // raw pointer.
    template <typename ModelStorage, typename = void>
    struct Storage
    {
        mutable std::remove_const_t<ModelStorage> m_model;
 
        using iterator = decltype(QRangeModelDetails::adl_begin(m_model));
        using const_iterator = decltype(QRangeModelDetails::adl_begin(m_model));
    };
 
    template <typename ModelStorage>
    struct Storage<ModelStorage,
                   std::void_t<decltype(QRangeModelDetails::adl_begin(std::declval<const ModelStorage&>()))>>
    {
        ModelStorage m_model;
 
        using iterator = decltype(QRangeModelDetails::adl_begin(m_model));
        using const_iterator = decltype(QRangeModelDetails::adl_begin(std::as_const(m_model)));
    };
 
    template <typename ModelStorage, typename PropertyStorage>
    struct ModelData : Storage<ModelStorage>,
                       PropertyStorage
    {
        using WrappedStorage = Storage<QRangeModelDetails::wrapped_t<ModelStorage>>;
        using iterator = typename WrappedStorage::iterator;
        using const_iterator = typename WrappedStorage::const_iterator;
 
        auto model() { return QRangeModelDetails::pointerTo(this->m_model); }
        auto model() const { return QRangeModelDetails::pointerTo(this->m_model); }
 
        template <typename Model = ModelStorage>
        ModelData(Model &&model)
            : Storage<ModelStorage>{std::forward<Model>(model)}
        {}
    };
} // namespace QRangeModelDetails
 
class QRangeModel;
// forward declare so that we can declare friends
template <typename, typename, typename> class QRangeModelAdapter;
 
class QRangeModelImplBase : public QtPrivate::QQuasiVirtualInterface<QRangeModelImplBase>
{
    using Self = QRangeModelImplBase;
    using QtPrivate::QQuasiVirtualInterface<Self>::Method;
 
public:
    // keep in sync with QRangeModel::AutoConnectPolicy
    enum class AutoConnectPolicy {
        None,
        Full,
        OnRead,
    };
 
    // keep in sync with QRangeModel::DropOperation
    enum class DropOperation {
        DontDrop,
        Automatic,
        OverwriteAndIgnore,
        OverwriteAndExtend,
        InsertAsSiblings,
        InsertAsChildren,
    };
 
    // overridable prototypes (quasi-pure-virtual methods)
    void invalidateCaches();
    bool setHeaderData(int section, Qt::Orientation orientation, const QVariant &data, int role);
    bool setData(const QModelIndex &index, const QVariant &data, int role);
    bool setItemData(const QModelIndex &index, const QMap<int, QVariant> &data);
    bool clearItemData(const QModelIndex &index);
    bool insertColumns(int column, int count, const QModelIndex &parent);
    bool removeColumns(int column, int count, const QModelIndex &parent);
    bool moveColumns(const QModelIndex &sourceParent, int sourceColumn, int count, const QModelIndex &destParent, int destColumn);
    bool insertRows(int row, int count, const QModelIndex &parent);
    bool removeRows(int row, int count, const QModelIndex &parent);
    bool moveRows(const QModelIndex &sourceParent, int sourceRow, int count, const QModelIndex &destParent, int destRow);
 
    QModelIndex index(int row, int column, const QModelIndex &parent) const;
    QModelIndex sibling(int row, int column, const QModelIndex &index) const;
    int rowCount(const QModelIndex &parent) const;
    int columnCount(const QModelIndex &parent) const;
    Qt::ItemFlags flags(const QModelIndex &index) const;
    QVariant headerData(int section, Qt::Orientation orientation, int role) const;
    QVariant data(const QModelIndex &index, int role) const;
    QMap<int, QVariant> itemData(const QModelIndex &index) const;
    inline QHash<int, QByteArray> roleNames() const;
    QModelIndex parent(const QModelIndex &child) const;
 
    void multiData(const QModelIndex &index, QModelRoleDataSpan roleDataSpan) const;
    void setAutoConnectPolicy();
 
    void interfaceVersion(int &version) const;
    void sort(int column, Qt::SortOrder order);
    QModelIndexList match(const QModelIndex &start, int role, const QVariant &value,
                          int hits, Qt::MatchFlags flags) const;
 
    Qt::DropActions adjustSupportedDragActions(Qt::DropActions dragActions);
    Qt::DropActions adjustSupportedDropActions(Qt::DropActions dropActions);
    QStringList mimeTypes() const;
    bool canDropMimeData(const QMimeData *data, Qt::DropAction action, int row, int column,
                         const QModelIndex &parent) const;
    bool dropMimeData(const QMimeData *data, Qt::DropAction action, int row, int column,
                      const QModelIndex &parent);
    QMimeData *mimeData(const QModelIndexList &indexes) const;
 
    // bindings for overriding
 
    using InvalidateCaches = Method<&Self::invalidateCaches>;
    using SetHeaderData = Method<&Self::setHeaderData>;
    using SetData = Method<&Self::setData>;
    using SetItemData = Method<&Self::setItemData>;
    using ClearItemData = Method<&Self::clearItemData>;
    using InsertColumns = Method<&Self::insertColumns>;
    using RemoveColumns = Method<&Self::removeColumns>;
    using MoveColumns = Method<&Self::moveColumns>;
    using InsertRows = Method<&Self::insertRows>;
    using RemoveRows = Method<&Self::removeRows>;
    using MoveRows = Method<&Self::moveRows>;
 
    using Index = Method<&Self::index>;
    using Sibling = Method<&Self::sibling>;
    using RowCount = Method<&Self::rowCount>;
    using ColumnCount = Method<&Self::columnCount>;
    using Flags = Method<&Self::flags>;
    using HeaderData = Method<&Self::headerData>;
    using Data = Method<&Self::data>;
    using ItemData = Method<&Self::itemData>;
    using RoleNames = Method<&Self::roleNames>;
    using Parent = Method<&Self::parent>;
 
    // 6.11
    using MultiData = Method<&Self::multiData>;
    using SetAutoConnectPolicy = Method<&Self::setAutoConnectPolicy>;
 
    // 6.12
    using InterfaceVersion = Method<&Self::interfaceVersion>;
    using Sort = Method<&Self::sort>;
    using Match = Method<&Self::match>;
    using AdjustSupportedDragActions = Method<&Self::adjustSupportedDragActions>;
    using AdjustSupportedDropActions = Method<&Self::adjustSupportedDropActions>;
 
    using MimeTypes = Method<&Self::mimeTypes>;
    using CanDropMimeData = Method<&Self::canDropMimeData>;
    using DropMimeData = Method<&Self::dropMimeData>;
    using MimeData = Method<&Self::mimeData>;
 
    template <typename C>
    using MethodTemplates = std::tuple<
        typename C::Destroy,
        typename C::InvalidateCaches,
        typename C::SetHeaderData,
        typename C::SetData,
        typename C::SetItemData,
        typename C::ClearItemData,
        typename C::InsertColumns,
        typename C::RemoveColumns,
        typename C::MoveColumns,
        typename C::InsertRows,
        typename C::RemoveRows,
        typename C::MoveRows,
        typename C::Index,
        typename C::Parent,
        typename C::Sibling,
        typename C::RowCount,
        typename C::ColumnCount,
        typename C::Flags,
        typename C::HeaderData,
        typename C::Data,
        typename C::ItemData,
        typename C::RoleNames,
        typename C::MultiData,
        typename C::SetAutoConnectPolicy,
        typename C::InterfaceVersion,
        typename C::Sort,
        typename C::Match,
        typename C::AdjustSupportedDragActions,
        typename C::AdjustSupportedDropActions,
        typename C::MimeTypes,
        typename C::CanDropMimeData,
        typename C::DropMimeData,
        typename C::MimeData
    >;
 
    static Q_CORE_EXPORT QRangeModelImplBase *getImplementation(QRangeModel *model);
    static Q_CORE_EXPORT const QRangeModelImplBase *getImplementation(const QRangeModel *model);
 
private:
    friend class QRangeModelPrivate;
    friend struct PropertyChangedHandler;
 
    QRangeModel *m_rangeModel;
 
protected:
    explicit QRangeModelImplBase(QRangeModel *itemModel)
        : m_rangeModel(itemModel)
    {}
 
    inline QModelIndex createIndex(int row, int column, const void *ptr = nullptr) const;
    inline QModelIndexList persistentIndexList() const;
    inline void changePersistentIndex(const QModelIndex &from, const QModelIndex &to);
    inline void dataChanged(const QModelIndex &from, const QModelIndex &to,
                            const QList<int> &roles);
    inline void beginResetModel();
    inline void endResetModel();
    inline void beginInsertColumns(const QModelIndex &parent, int start, int count);
    inline void endInsertColumns();
    inline void beginRemoveColumns(const QModelIndex &parent, int start, int count);
    inline void endRemoveColumns();
    inline bool beginMoveColumns(const QModelIndex &sourceParent, int sourceFirst, int sourceLast,
                                 const QModelIndex &destParent, int destRow);
    inline void endMoveColumns();
    inline void beginInsertRows(const QModelIndex &parent, int start, int count);
    inline void endInsertRows();
    inline void beginRemoveRows(const QModelIndex &parent, int start, int count);
    inline void endRemoveRows();
    inline bool beginMoveRows(const QModelIndex &sourceParent, int sourceFirst, int sourceLast,
                              const QModelIndex &destParent, int destRow);
    inline void endMoveRows();
    inline void beginLayoutChange();
    inline void endLayoutChange();
    inline AutoConnectPolicy autoConnectPolicy() const;
    inline static Qt::partial_ordering compareData(const QVariant &lhs, const QVariant &rhs,
                                                   const QCollator *collator);
 
public:
    inline QAbstractItemModel &itemModel();
    inline const QAbstractItemModel &itemModel() const;
 
    // implemented in qrangemodel.cpp
    Q_CORE_EXPORT static QHash<int, QByteArray> roleNamesForMetaObject(const QAbstractItemModel &model,
                                                                       const QMetaObject &metaObject);
    Q_CORE_EXPORT static QHash<int, QByteArray> roleNamesForSimpleType();
 
protected:
    Q_CORE_EXPORT QScopedValueRollback<bool> blockDataChangedDispatch();
 
    Q_CORE_EXPORT static QHash<int, QMetaProperty> roleProperties(const QAbstractItemModel &model,
                                                                  const QMetaObject &metaObject);
    Q_CORE_EXPORT static QHash<int, QMetaProperty> columnProperties(const QMetaObject &metaObject);
    Q_CORE_EXPORT static bool connectProperty(const QModelIndex &index, const QObject *item,
                                              QRangeModelDetails::AutoConnectContext *context,
                                              int role, const QMetaProperty &property);
    Q_CORE_EXPORT static bool connectPropertyConst(const QModelIndex &index, const QObject *item,
                                                   QRangeModelDetails::AutoConnectContext *context,
                                                   int role, const QMetaProperty &property);
    Q_CORE_EXPORT static bool connectProperties(const QModelIndex &index, const QObject *item,
                                                QRangeModelDetails::AutoConnectContext *context,
                                                const QHash<int, QMetaProperty> &properties);
    Q_CORE_EXPORT static bool connectPropertiesConst(const QModelIndex &index, const QObject *item,
                                                     QRangeModelDetails::AutoConnectContext *context,
                                                     const QHash<int, QMetaProperty> &properties);
    Q_CORE_EXPORT int sortRole() const;
    Q_CORE_EXPORT const QCollator *sortCollator() const;
    Q_CORE_EXPORT QCollator matchCollator() const;
 
    Q_CORE_EXPORT static QVariant convertMatchValue(const QVariant &value, Qt::MatchFlags flags);
    Q_CORE_EXPORT static bool matchValue(const QString &itemData, const QVariant &value,
                                         Qt::MatchFlags flags);
    Q_CORE_EXPORT static bool matchValue(const QString &itemData, const QVariant &value,
                                         Qt::MatchFlags flags, const QCollator &collator);
    static bool matchValue(const QVariant &itemData, const QVariant &value, Qt::MatchFlags flags,
                           const QCollator &collator)
    {
        if ((flags & Qt::MatchTypeMask) == Qt::MatchExactly)
            return itemData == value;
        return matchValue(itemData.toString(), value, flags, collator);
    }
 
    Q_CORE_EXPORT bool dropDataOnItem(const QMimeData *data, const QModelIndex &index);
};
 
template <typename Structure, typename Range,
          typename Protocol = QRangeModelDetails::table_protocol_t<Range>>
class QRangeModelImpl
        : public QtPrivate::QQuasiVirtualSubclass<QRangeModelImpl<Structure, Range, Protocol>,
                                                  QRangeModelImplBase>,
          private QtPrivate::CompactStorage<Protocol>
{
public:
    using range_type = QRangeModelDetails::wrapped_t<Range>;
    using range_features = QRangeModelDetails::range_traits<range_type>;
    using row_reference = decltype(*QRangeModelDetails::adl_begin(std::declval<range_type&>()));
    using row_type = std::remove_reference_t<row_reference>;
    using wrapped_row_type = QRangeModelDetails::wrapped_t<row_type>;
    using row_features = QRangeModelDetails::range_traits<wrapped_row_type>;
    using row_traits = QRangeModelDetails::row_traits<std::remove_cv_t<wrapped_row_type>>;
    using protocol_type = QRangeModelDetails::wrapped_t<Protocol>;
    using protocol_traits = QRangeModelDetails::protocol_traits<Range, protocol_type>;
 
    static constexpr bool itemsAreQObjects = std::is_base_of_v<QObject, std::remove_pointer_t<
                                                               typename row_traits::item_type>>;
    static constexpr bool rowsAreQObjects = std::is_base_of_v<QObject, wrapped_row_type>
                                         && row_traits::hasMetaObject; // not treated as tuple
 
    using ModelData = QRangeModelDetails::ModelData<std::conditional_t<
                                                        std::is_pointer_v<Range>,
                                                        Range, std::remove_reference_t<Range>
                                                    >,
                                                    QRangeModelDetails::PropertyData<QRangeModelDetails::has_metaobject_v<typename row_traits::item_type>,
                                                                 itemsAreQObjects || rowsAreQObjects
                                                                >
                                                   >;
    using ProtocolStorage = QtPrivate::CompactStorage<Protocol>;
 
    using const_row_reference = decltype(*std::declval<typename ModelData::const_iterator&>());
 
    static_assert(!QRangeModelDetails::is_any_of<range_type, std::optional>() &&
                  !QRangeModelDetails::is_any_of<row_type, std::optional>(),
                  "Currently, std::optional is not supported for ranges and rows, as "
                  "it has range semantics in c++26. Once the required behavior is clarified, "
                  "std::optional for ranges and rows will be supported.");
 
protected:
 
    using Self = QRangeModelImpl<Structure, Range, Protocol>;
    using Ancestor = QtPrivate::QQuasiVirtualSubclass<Self, QRangeModelImplBase>;
 
    Structure& that() { return static_cast<Structure &>(*this); }
    const Structure& that() const { return static_cast<const Structure &>(*this); }
 
    template <typename C>
    static constexpr int size(const C &c)
    {
        if (!QRangeModelDetails::isValid(c))
            return 0;
 
        if constexpr (QRangeModelDetails::test_size<C>()) {
            using std::size;
            return int(size(c));
        } else {
#if defined(__cpp_lib_ranges)
            using std::ranges::distance;
#else
            using std::distance;
#endif
            using container_type = std::conditional_t<QRangeModelDetails::range_traits<C>::has_cbegin,
                                                      const QRangeModelDetails::wrapped_t<C>,
                                                      QRangeModelDetails::wrapped_t<C>>;
            container_type& container = const_cast<container_type &>(QRangeModelDetails::refTo(c));
            return int(distance(QRangeModelDetails::adl_begin(container),
                                QRangeModelDetails::adl_end(container)));
        }
    }
 
    static constexpr int static_row_count = QRangeModelDetails::static_size_v<range_type>;
    static constexpr bool rows_are_raw_pointers = std::is_pointer_v<row_type>;
    static constexpr bool rows_are_owning_or_raw_pointers =
            QRangeModelDetails::is_owning_or_raw_pointer<row_type>();
    static constexpr int static_column_count = QRangeModelDetails::static_size_v<row_type>;
    static constexpr bool one_dimensional_range = static_column_count == 0;
 
    auto maybeBlockDataChangedDispatch()
    {
        if constexpr (itemsAreQObjects || rowsAreQObjects)
            return this->blockDataChangedDispatch();
        else
            return false;
    }
 
    // A row might be a value (or range of values), or a pointer.
    // row_ptr is always a pointer, and const_row_ptr is a pointer to const.
    using row_ptr = wrapped_row_type *;
    using const_row_ptr = const wrapped_row_type *;
 
    template <typename T>
    static constexpr bool has_metaobject = QRangeModelDetails::has_metaobject_v<
                                                std::remove_pointer_t<std::remove_reference_t<T>>>;
 
    // A iterator type to use as the input iterator with the
    // range_type::insert(pos, start, end) overload if available (it is in
    // std::vector, but not in QList). Generates a prvalue when dereferenced,
    // which then gets moved into the newly constructed row, which allows us to
    // implement insertRows() for move-only row types.
    struct EmptyRowGenerator
    {
        using value_type = row_type;
        using reference = value_type;
        using pointer = value_type *;
        using iterator_category = std::input_iterator_tag;
        using difference_type = int;
 
        value_type operator*() { return impl->makeEmptyRow(parentRow); }
        EmptyRowGenerator &operator++() { ++n; return *this; }
        friend bool operator==(const EmptyRowGenerator &lhs, const EmptyRowGenerator &rhs) noexcept
        { return lhs.n == rhs.n; }
        friend bool operator!=(const EmptyRowGenerator &lhs, const EmptyRowGenerator &rhs) noexcept
        { return !(lhs == rhs); }
 
        difference_type n = 0;
        Structure *impl = nullptr;
        const row_ptr parentRow = nullptr;
    };
 
    // If we have a move-only row_type and can add/remove rows, then the range
    // must have an insert-from-range overload.
    static_assert(static_row_count || range_features::has_insert_range
                                   || std::is_copy_constructible_v<row_type>,
                  "The range holding a move-only row-type must support insert(pos, start, end)");
 
    using AutoConnectPolicy = typename Ancestor::AutoConnectPolicy;
    using DropOperation = typename Ancestor::DropOperation;
 
public:
    static constexpr bool isMutable()
    {
        return range_features::is_mutable && row_features::is_mutable
            && std::is_reference_v<row_reference>
            && Structure::is_mutable_impl;
    }
    static constexpr bool dynamicRows() { return isMutable() && static_row_count < 0; }
    static constexpr bool dynamicColumns() { return static_column_count < 0; }
 
    explicit QRangeModelImpl(Range &&model, Protocol&& protocol, QRangeModel *itemModel)
        : Ancestor(itemModel)
        , ProtocolStorage{std::forward<Protocol>(protocol)}
        , m_data{std::forward<Range>(model)}
    {
    }
 
 
    // static interface, called by QRangeModelImplBase
 
    void interfaceVersion(int &versionNumber) const
    {
        versionNumber = QT_VERSION;
    }
 
    void invalidateCaches() { m_data.invalidateCaches(); }
 
    // Not implemented
    bool setHeaderData(int , Qt::Orientation , const QVariant &, int ) { return false; }
 
    // actual implementations
    QModelIndex index(int row, int column, const QModelIndex &parent) const
    {
        if (row < 0 || column < 0 || column >= columnCount(parent)
                                  || row >= rowCount(parent)) {
            return {};
        }
 
        return that().indexImpl(row, column, parent);
    }
 
    QModelIndex sibling(int row, int column, const QModelIndex &index) const
    {
        if (row == index.row() && column == index.column())
            return index;
 
        // we use indexes at column -1 in drag'n'drop handling to mark full rows
        if (column >= this->columnCount({}))
            return {};
 
        if (row == index.row())
            return this->createIndex(row, column, index.constInternalPointer());
 
        const_row_ptr parentRow = static_cast<const_row_ptr>(index.constInternalPointer());
        const auto siblingCount = size(that().childrenOf(parentRow));
        if (row < 0 || row >= int(siblingCount))
            return {};
        return this->createIndex(row, column, parentRow);
    }
 
    Qt::ItemFlags flags(const QModelIndex &index) const
    {
        if (!index.isValid()) {
            if constexpr (isMutable())
                return Qt::ItemIsDropEnabled;
            else
                return Qt::NoItemFlags;
        }
 
        // try customization
        std::optional<Qt::ItemFlags> customFlags;
        if constexpr (QRangeModelDetails::hasRowFlags<wrapped_row_type>) {
            const_row_reference row = rowData(index);
            if (QRangeModelDetails::isValid(row)) {
                customFlags = QRangeModelDetails::QRangeModelRowOptions<wrapped_row_type>::flags(
                    QRangeModelDetails::refTo(row)
                );
            }
        }
 
        readAt(index, [&customFlags](auto &&ref){
            Q_UNUSED(ref);
            using wrapped_value_type = q20::remove_cvref_t<QRangeModelDetails::wrapped_t<decltype(ref)>>;
            if constexpr (QRangeModelDetails::item_access<wrapped_value_type>::hasFlags) {
                using ItemAccess = QRangeModelDetails::QRangeModelItemAccess<wrapped_value_type>;
                if (QRangeModelDetails::isValid(ref)) {
                    customFlags = ItemAccess::flags(QRangeModelDetails::refTo(ref));
                    return true;
                }
            }
            return false;
        });
 
        Qt::ItemFlags f = customFlags ? *customFlags : Structure::defaultFlags();
        // adjust custom flags based on what is not possible
        if constexpr (!isMutable())
            f &= ~(Qt::ItemIsEditable | Qt::ItemIsDropEnabled);
        if (index.column())
            f |= Qt::ItemNeverHasChildren;
        if (customFlags)
            return f;
 
        // compute flags ourselves
        if (!this->itemModel().mimeTypes().isEmpty()) {
            f |= Qt::ItemIsDragEnabled;
            if constexpr (isMutable())
                f |= Qt::ItemIsDropEnabled;
        }
 
        if constexpr (QRangeModelDetails::is_owning_or_raw_pointer<row_type>()) {
            // pointer rows might be null
            const_row_reference row = rowData(index);
            if (!QRangeModelDetails::isValid(row))
                f &= ~Qt::ItemIsDragEnabled;
        }
 
        if constexpr (isMutable()) {
            // Note: Read-only items are still droppable - we can't know here
            // whether the model will insert data as new rows or children, or if
            // it will overwrite the data of the dropped-on item. So we allow
            // dropping on items that are not editable.
            if constexpr (row_traits::hasMetaObject) {
                if (index.column() < row_traits::fixed_size()) {
                    const QMetaObject mo = wrapped_row_type::staticMetaObject;
                    const QMetaProperty prop = mo.property(index.column() + mo.propertyOffset());
                    if (prop.isWritable())
                        f |= Qt::ItemIsEditable;
                }
            } else if constexpr (static_column_count <= 0) {
                using item_type = typename row_traits::item_type;
                if constexpr (QRangeModelDetails::is_owning_or_raw_pointer<item_type>()) {
                    // pointer items might be null
                    if (!readAt(index, [](auto &&i){ return QRangeModelDetails::isValid(i); }))
                        f &= ~Qt::ItemIsDragEnabled;
                }
                f |= Qt::ItemIsEditable;
            } else if constexpr (std::is_reference_v<row_reference> && !std::is_const_v<row_reference>) {
                // we want to know if the elements in the tuple are const; they'd always be, if
                // we didn't remove the const of the range first.
                const_row_reference row = rowData(index);
                row_reference mutableRow = const_cast<row_reference>(row);
                if (QRangeModelDetails::isValid(mutableRow)) {
                    row_traits::for_element_at(mutableRow, index.column(), [&f](auto &&ref){
                        using target_type = decltype(ref);
                        if constexpr (QRangeModelDetails::is_owning_or_raw_pointer<target_type>()) {
                            // pointer items might be null
                            if (!QRangeModelDetails::isValid(ref))
                                f &= ~Qt::ItemIsDragEnabled;
                        }
                        if constexpr (std::is_const_v<std::remove_reference_t<target_type>>)
                            f &= ~Qt::ItemIsEditable;
                        else if constexpr (std::is_lvalue_reference_v<target_type>)
                            f |= Qt::ItemIsEditable;
                    });
                } else {
                    // If there's no usable value stored in the row, then we can't
                    // do anything with this item, except perhaps drop data into it
                    f &= ~Qt::ItemIsEditable;
                }
            }
        }
        return f;
    }
 
    QVariant headerData(int section, Qt::Orientation orientation, int role) const
    {
        QVariant result;
        if constexpr (QRangeModelDetails::hasHeaderData<wrapped_row_type>) {
            if (orientation == Qt::Horizontal) {
                result = QRangeModelDetails::QRangeModelRowOptions<wrapped_row_type>::headerData(
                    section, role
                );
                if (result.isValid())
                    return result;
            }
        }
 
        if (role != Qt::DisplayRole || orientation != Qt::Horizontal
         || section < 0 || section >= columnCount({})) {
            return this->itemModel().QAbstractItemModel::headerData(section, orientation, role);
        }
 
        result = row_traits::column_name(section);
        if (!result.isValid())
            result = this->itemModel().QAbstractItemModel::headerData(section, orientation, role);
        return result;
    }
 
    QVariant data(const QModelIndex &index, int role) const
    {
        if (!index.isValid())
            return {};
 
        QModelRoleData result(role);
        multiData(index, result);
        return std::move(result.data());
    }
 
    static constexpr bool isRangeModelRole(int role)
    {
        return role == Qt::RangeModelDataRole
            || role == Qt::RangeModelAdapterRole;
    }
 
    static constexpr bool isPrimaryRole(int role)
    {
        return role == Qt::DisplayRole || role == Qt::EditRole;
    }
 
    QMap<int, QVariant> itemData(const QModelIndex &index) const
    {
        QMap<int, QVariant> result;
 
        if (index.isValid()) {
            // optimisation for items backed by a QMap<int, QVariant> or equivalent
            if (!readAt(index, [&result](const auto &value) {
                if constexpr (std::is_convertible_v<decltype(value), decltype(result)>) {
                    result = value;
                    return true;
                }
                return false;
            })) {
                const auto roles = this->itemModel().roleNames().keys();
                QVarLengthArray<QModelRoleData, 16> roleDataArray;
                roleDataArray.reserve(roles.size());
                for (auto role : roles) {
                    if (isRangeModelRole(role))
                        continue;
                    roleDataArray.emplace_back(role);
                }
                QModelRoleDataSpan roleDataSpan(roleDataArray);
                multiData(index, roleDataSpan);
 
                for (QModelRoleData &roleData : roleDataSpan) {
                    if (roleData.data().isValid())
                        result[roleData.role()] = std::move(roleData.data());
                }
            }
        }
        return result;
    }
 
    struct ItemReader
    {
        template <typename value_type>
        bool operator()(const value_type &value) const
        {
            using multi_role = QRangeModelDetails::is_multi_role<value_type>;
            using wrapped_value_type = QRangeModelDetails::wrapped_t<value_type>;
 
            const auto readModelData = [&value](QModelRoleData &roleData){
                if (!QRangeModelDetails::isValid(value)) {
                    roleData.clearData();
                    return true;
                }
 
                const int role = roleData.role();
                if (role == Qt::RangeModelDataRole) {
                    // Qt QML support: "modelData" role returns the entire multi-role item.
                    // QML can only use raw pointers to QObject (so we unwrap), and gadgets
                    // only by value (so we take the reference).
                    if constexpr (std::is_copy_assignable_v<wrapped_value_type>)
                        roleData.setData(QVariant::fromValue(QRangeModelDetails::refTo(value)));
                    else
                        roleData.setData(QVariant::fromValue(QRangeModelDetails::pointerTo(value)));
                } else if (role == Qt::RangeModelAdapterRole) {
                    // for QRangeModelAdapter however, we want to respect smart pointer wrappers
                    if constexpr (std::is_copy_assignable_v<value_type>)
                        roleData.setData(QVariant::fromValue(value));
                    else
                        roleData.setData(QVariant::fromValue(QRangeModelDetails::pointerTo(value)));
                } else {
                    return false;
                }
                return true;
            };
 
            if constexpr (QRangeModelDetails::item_access<wrapped_value_type>::hasReadRole) {
                using ItemAccess = QRangeModelDetails::QRangeModelItemAccess<wrapped_value_type>;
                for (auto &roleData : roleDataSpan) {
                    if (!readModelData(roleData)) {
                        roleData.setData(ItemAccess::readRole(QRangeModelDetails::refTo(value),
                                                              roleData.role()));
                    }
                }
            } else if constexpr (multi_role()) {
                const auto roleNames = [this]() -> QHash<int, QByteArray> {
                    Q_UNUSED(this);
                    if constexpr (!multi_role::int_key)
                        return that->itemModel().roleNames();
                    else
                        return {};
                }();
                using key_type = typename value_type::key_type;
                for (auto &roleData : roleDataSpan) {
                    const auto &it = [&roleNames, &value, role = roleData.role()]{
                        Q_UNUSED(roleNames);
                        if constexpr (multi_role::int_key)
                            return value.find(key_type(role));
                        else
                            return value.find(roleNames.value(role));
                    }();
                    if (it != QRangeModelDetails::adl_end(value))
                        roleData.setData(QRangeModelDetails::value(it));
                    else
                        roleData.clearData();
                }
            } else if constexpr (has_metaobject<value_type>) {
                if (row_traits::fixed_size() <= 1) {
                    for (auto &roleData : roleDataSpan) {
                        if (!readModelData(roleData)) {
                            roleData.setData(that->readRole(index, roleData.role(),
                                                            QRangeModelDetails::pointerTo(value)));
                        }
                    }
                } else if (index.column() <= row_traits::fixed_size()) {
                    for (auto &roleData : roleDataSpan) {
                        const int role = roleData.role();
                        if (isPrimaryRole(role)) {
                            roleData.setData(that->readProperty(index,
                                                                QRangeModelDetails::pointerTo(value)));
                        } else {
                            roleData.clearData();
                        }
                    }
                }
            } else {
                for (auto &roleData : roleDataSpan) {
                    const int role = roleData.role();
                    if (isPrimaryRole(role) || isRangeModelRole(role))
                        roleData.setData(read(value));
                    else
                        roleData.clearData();
                }
            }
            return true;
        }
 
        const QModelIndex &index;
        QModelRoleDataSpan roleDataSpan;
        const QRangeModelImpl * const that;
    };
 
    void multiData(const QModelIndex &index, QModelRoleDataSpan roleDataSpan) const
    {
        if (!readAt(index, ItemReader{index, roleDataSpan, this})) {
            for (auto &roleData : roleDataSpan)
                roleData.clearData();
        }
    }
 
    bool setData(const QModelIndex &index, const QVariant &data, int role)
    {
        if (!index.isValid())
            return false;
 
        if constexpr (isMutable()) {
            auto emitDataChanged = qScopeGuard([this, &index, role]{
                Q_EMIT this->dataChanged(index, index,
                                    role == Qt::EditRole || role == Qt::RangeModelDataRole
                                || role == Qt::RangeModelAdapterRole
                                        ? QList<int>{} : QList<int>{role});
            });
            // we emit dataChanged at the end, block dispatches from auto-connected properties
            [[maybe_unused]] auto dataChangedBlocker = maybeBlockDataChangedDispatch();
 
            const auto writeData = [this, column = index.column(), &data, role](auto &&target) -> bool {
                using value_type = q20::remove_cvref_t<decltype(target)>;
                using wrapped_value_type = QRangeModelDetails::wrapped_t<value_type>;
                using multi_role = QRangeModelDetails::is_multi_role<value_type>;
 
                if constexpr (std::conjunction_v<QRangeModelDetails::is_any_owning_ptr<value_type>,
                                                 std::is_default_constructible<wrapped_value_type>>) {
                    if (!QRangeModelDetails::isValid(target))
                        target.reset(new wrapped_value_type);
                }
 
                auto setRangeModelDataRole = [&target, &data]{
                    constexpr auto targetMetaType = QMetaType::fromType<value_type>();
                    const auto dataMetaType = data.metaType();
                    constexpr bool isWrapped = QRangeModelDetails::is_wrapped<value_type>();
                    if constexpr (!std::is_copy_assignable_v<wrapped_value_type>) {
                        // we don't support replacing objects that are stored as raw pointers,
                        // as this makes object ownership very messy. But we can replace objects
                        // stored in smart pointers, and we can initialize raw nullptr objects.
                        if constexpr (isWrapped) {
                            constexpr bool is_raw_pointer = std::is_pointer_v<value_type>;
                            if constexpr (!is_raw_pointer && std::is_copy_assignable_v<value_type>) {
                                if (data.canConvert(targetMetaType)) {
                                    target = data.value<value_type>();
                                    return true;
                                }
                            } else if constexpr (is_raw_pointer) {
                                if (!QRangeModelDetails::isValid(target) && data.canConvert(targetMetaType)) {
                                    target = data.value<value_type>();
                                    return true;
                                }
                            } else {
                                Q_UNUSED(target);
                            }
                        }
                        // Otherwise we have a move-only or polymorph type. fall through to
                        // error handling.
                    } else if constexpr (isWrapped) {
                        if (QRangeModelDetails::isValid(target)) {
                            auto &targetRef = QRangeModelDetails::refTo(target);
                            // we need to get a wrapped value type out of the QVariant, which
                            // might carry a pointer. We have to try all alternatives.
                            if (const auto mt = QMetaType::fromType<wrapped_value_type>();
                                data.canConvert(mt)) {
                                targetRef = data.value<wrapped_value_type>();
                                return true;
                            } else if (const auto mtp = QMetaType::fromType<wrapped_value_type *>();
                                        data.canConvert(mtp)) {
                                targetRef = *data.value<wrapped_value_type *>();
                                return true;
                            }
                        }
                    } else if (targetMetaType == dataMetaType) {
                        QRangeModelDetails::refTo(target) = data.value<value_type>();
                        return true;
                    } else if (dataMetaType.flags() & QMetaType::PointerToGadget) {
                        QRangeModelDetails::refTo(target) = *data.value<value_type *>();
                        return true;
                    }
#ifndef QT_NO_DEBUG
                    qCritical("Not able to assign %s to %s",
                                qPrintable(QDebug::toString(data)), targetMetaType.name());
#endif
                    return false;
                };
 
                if constexpr (QRangeModelDetails::item_access<wrapped_value_type>::hasWriteRole) {
                    using ItemAccess = QRangeModelDetails::QRangeModelItemAccess<wrapped_value_type>;
                    if (isRangeModelRole(role))
                        return setRangeModelDataRole();
                    return ItemAccess::writeRole(QRangeModelDetails::refTo(target), data, role);
                } else if constexpr (has_metaobject<value_type>) {
                    if (row_traits::fixed_size() <= 1) { // multi-role value
                        if (isRangeModelRole(role))
                            return setRangeModelDataRole();
                        return writeRole(role, QRangeModelDetails::pointerTo(target), data);
                    } else if (column <= row_traits::fixed_size() // multi-column
                            && (isPrimaryRole(role) || isRangeModelRole(role))) {
                        return writeProperty(column, QRangeModelDetails::pointerTo(target), data);
                    }
                } else if constexpr (multi_role::value) {
                    Qt::ItemDataRole roleToSet = Qt::ItemDataRole(role);
                    // If there is an entry for EditRole, overwrite that; otherwise,
                    // set the entry for DisplayRole.
                    const auto roleNames = [this]() -> QHash<int, QByteArray> {
                        Q_UNUSED(this);
                        if constexpr (!multi_role::int_key)
                            return this->itemModel().roleNames();
                        else
                            return {};
                    }();
                    if (role == Qt::EditRole) {
                        if constexpr (multi_role::int_key) {
                            if (target.find(roleToSet) == target.end())
                                roleToSet = Qt::DisplayRole;
                        } else {
                            if (target.find(roleNames.value(roleToSet)) == target.end())
                                roleToSet = Qt::DisplayRole;
                        }
                    }
                    if constexpr (multi_role::int_key)
                        return write(target[roleToSet], data);
                    else
                        return write(target[roleNames.value(roleToSet)], data);
                } else if (isPrimaryRole(role) || isRangeModelRole(role)) {
                    return write(target, data);
                }
                return false;
            };
 
            if (!writeAt(index, writeData)) {
                emitDataChanged.dismiss();
                return false;
            } else if constexpr (itemsAreQObjects || rowsAreQObjects) {
                if (isRangeModelRole(role) && this->autoConnectPolicy() == AutoConnectPolicy::Full) {
                    if (QObject *item = data.value<QObject *>())
                        Self::connectProperties(index, item, m_data.context, m_data.properties);
                }
            }
            return true;
        }
        return false;
    }
 
    template <typename LHS, typename RHS>
    void updateTarget(LHS &org, RHS &&copy) noexcept
    {
        if constexpr (std::is_pointer_v<RHS>)
            return;
        else if constexpr (std::is_assignable_v<LHS, RHS>)
            org = std::forward<RHS>(copy);
        else
            qSwap(org, copy);
    }
    template <typename LHS, typename RHS>
    void updateTarget(LHS *org, RHS &&copy) noexcept
    {
        updateTarget(*org, std::forward<RHS>(copy));
    }
 
    bool setItemData(const QModelIndex &index, const QMap<int, QVariant> &data)
    {
        if (!index.isValid() || data.isEmpty())
            return false;
 
        if constexpr (isMutable()) {
            auto emitDataChanged = qScopeGuard([this, &index, &data]{
                Q_EMIT this->dataChanged(index, index, data.keys());
            });
            // we emit dataChanged at the end, block dispatches from auto-connected properties
            [[maybe_unused]] auto dataChangedBlocker = maybeBlockDataChangedDispatch();
 
            bool tried = false;
            auto writeItemData = [this, &tried, &data](auto &target) -> bool {
                Q_UNUSED(this);
                using value_type = q20::remove_cvref_t<decltype(target)>;
                using multi_role = QRangeModelDetails::is_multi_role<value_type>;
                using wrapped_value_type = QRangeModelDetails::wrapped_t<value_type>;
 
                // transactional: if possible, modify a copy and only
                // update target if all values from data could be stored.
                auto makeCopy = [](const value_type &original){
                    if constexpr (!std::is_copy_assignable_v<wrapped_value_type>)
                        return QRangeModelDetails::pointerTo(original); // no transaction support
                    else if constexpr (std::is_pointer_v<decltype(original)>)
                        return *original;
                    else if constexpr (std::is_copy_assignable_v<value_type>)
                        return original;
                    else
                        return QRangeModelDetails::pointerTo(original);
                };
 
                const auto roleNames = this->itemModel().roleNames();
 
                if constexpr (QRangeModelDetails::item_access<wrapped_value_type>::hasWriteRole) {
                    tried = true;
                    using ItemAccess = QRangeModelDetails::QRangeModelItemAccess<wrapped_value_type>;
                    const auto roles = roleNames.keys();
                    auto targetCopy = makeCopy(target);
                    for (int role : roles) {
                        if (!ItemAccess::writeRole(QRangeModelDetails::refTo(targetCopy),
                                                   data.value(role), role)) {
                            return false;
                        }
                    }
                    updateTarget(target, std::move(targetCopy));
                    return true;
                } else if constexpr (multi_role()) {
                    using key_type = typename value_type::key_type;
                    tried = true;
                    const auto roleName = [&roleNames](int role) {
                        return roleNames.value(role);
                    };
 
                    // transactional: only update target if all values from data
                    // can be stored. Storing never fails with int-keys.
                    if constexpr (!multi_role::int_key)
                    {
                        auto invalid = std::find_if(data.keyBegin(), data.keyEnd(),
                            [&roleName](int role) { return roleName(role).isEmpty(); }
                        );
 
                        if (invalid != data.keyEnd()) {
#ifndef QT_NO_DEBUG
                            qWarning("No role name set for %d", *invalid);
#endif
                            return false;
                        }
                    }
 
                    for (auto &&[role, value] : data.asKeyValueRange()) {
                        if constexpr (multi_role::int_key)
                            target[static_cast<key_type>(role)] = value;
                        else
                            target[QString::fromUtf8(roleName(role))] = value;
                    }
                    return true;
                } else if constexpr (has_metaobject<value_type>) {
                    if (row_traits::fixed_size() <= 1) {
                        tried = true;
                        auto targetCopy = makeCopy(target);
                        for (auto &&[role, value] : data.asKeyValueRange()) {
                            if (isRangeModelRole(role))
                                continue;
                            if (!writeRole(role, QRangeModelDetails::pointerTo(targetCopy), value)) {
                                const QByteArray roleName = roleNames.value(role);
#ifndef QT_NO_DEBUG
                                qWarning("Failed to write value '%s' to role '%s'",
                                         qPrintable(QDebug::toString(value)), roleName.data());
#endif
                                return false;
                            }
                        }
                        updateTarget(target, std::move(targetCopy));
                        return true;
                    }
                }
                return false;
            };
 
            if (!writeAt(index, writeItemData)) {
                emitDataChanged.dismiss();
                if (!tried)
                    return this->itemModel().QAbstractItemModel::setItemData(index, data);
            }
            return true;
        }
        return false;
    }
 
    bool clearItemData(const QModelIndex &index)
    {
        if (!index.isValid())
            return false;
 
        if constexpr (isMutable()) {
            auto emitDataChanged = qScopeGuard([this, &index]{
                Q_EMIT this->dataChanged(index, index, {});
            });
 
            auto clearData = [column = index.column()](auto &&target) {
                if constexpr (row_traits::hasMetaObject) {
                    if (row_traits::fixed_size() <= 1) {
                        // multi-role object/gadget: reset all properties
                        return resetProperty(-1, QRangeModelDetails::pointerTo(target));
                    } else if (column <= row_traits::fixed_size()) {
                        return resetProperty(column, QRangeModelDetails::pointerTo(target));
                    }
                } else { // normal structs, values, associative containers
                    target = {};
                    return true;
                }
                return false;
            };
 
            if (!writeAt(index, clearData)) {
                emitDataChanged.dismiss();
                return false;
            }
            return true;
        }
        return false;
    }
 
    QHash<int, QByteArray> roleNames() const
    {
        // will be 'void' if columns don't all have the same type
        using item_type = QRangeModelDetails::wrapped_t<typename row_traits::item_type>;
        using item_traits = typename QRangeModelDetails::item_traits<item_type>;
        return item_traits::roleNames(this);
    }
 
    bool autoConnectPropertiesInRow(const row_type &row, int rowIndex, const QModelIndex &parent) const
    {
        if (!QRangeModelDetails::isValid(row))
            return true; // nothing to do
        return row_traits::for_each_element(QRangeModelDetails::refTo(row),
                                            this->itemModel().index(rowIndex, 0, parent),
                                            [this](const QModelIndex &index, const QObject *item) {
            if constexpr (isMutable())
                return Self::connectProperties(index, item, m_data.context, m_data.properties);
            else
                return Self::connectPropertiesConst(index, item, m_data.context, m_data.properties);
        });
    }
 
    void clearConnectionInRow(const row_type &row, int rowIndex, const QModelIndex &parent) const
    {
        if (!QRangeModelDetails::isValid(row))
            return;
        row_traits::for_each_element(QRangeModelDetails::refTo(row),
                                     this->itemModel().index(rowIndex, 0, parent),
                                     [this](const QModelIndex &, const QObject *item) {
            m_data.connections.removeIf([item](const auto &connection) {
                return connection.sender == item;
            });
            return true;
        });
    }
 
    void setAutoConnectPolicy()
    {
        if constexpr (itemsAreQObjects || rowsAreQObjects) {
            using item_type = std::remove_pointer_t<typename row_traits::item_type>;
            using Mapping = QRangeModelDetails::AutoConnectContext::AutoConnectMapping;
 
            delete m_data.context;
            m_data.connections = {};
            switch (this->autoConnectPolicy()) {
            case AutoConnectPolicy::None:
                m_data.context = nullptr;
                break;
            case AutoConnectPolicy::Full:
                m_data.context = new QRangeModelDetails::AutoConnectContext(&this->itemModel());
                if constexpr (itemsAreQObjects) {
                    m_data.properties = QRangeModelImplBase::roleProperties(this->itemModel(),
                                                                            item_type::staticMetaObject);
                    m_data.context->mapping = Mapping::Roles;
                } else {
                    m_data.properties = QRangeModelImplBase::columnProperties(wrapped_row_type::staticMetaObject);
                    m_data.context->mapping = Mapping::Columns;
                }
                if (!m_data.properties.isEmpty())
                    that().autoConnectPropertiesImpl();
                break;
            case AutoConnectPolicy::OnRead:
                m_data.context = new QRangeModelDetails::AutoConnectContext(&this->itemModel());
                if constexpr (itemsAreQObjects) {
                    m_data.context->mapping = Mapping::Roles;
                } else {
                    m_data.properties = QRangeModelImplBase::columnProperties(wrapped_row_type::staticMetaObject);
                    m_data.context->mapping = Mapping::Columns;
                }
                break;
            }
        } else {
#ifndef QT_NO_DEBUG
            qWarning("All items in the range must be QObject subclasses");
#endif
        }
    }
 
    struct unordered {
        friend constexpr bool operator<(unordered, QtPrivate::CompareAgainstLiteralZero) noexcept
        { return false; }
        friend constexpr bool operator>(unordered, QtPrivate::CompareAgainstLiteralZero) noexcept
        { return false; }
    };
 
    struct Compare
    {
        template <typename C, typename LessThan>
        using sortMember_test = decltype(std::declval<C&>().sort(std::declval<LessThan &&>()));
        static constexpr bool hasSortMember = qxp::is_detected_v<sortMember_test, range_type, Compare>;
 
        template <typename Stringish>
        using collatedCompare_test = decltype(
            std::declval<const QCollator&>().compare(std::declval<const Stringish&>(),
                                                     std::declval<const Stringish&>())
        );
        template <typename Stringish>
        static constexpr bool hasCollatedCompare = qxp::is_detected_v<collatedCompare_test,
                                                                        Stringish>;
 
 
        Compare(const QRangeModelImpl *impl, int column, Qt::SortOrder order)
            : that(impl), m_index(impl->createIndex(-1, column, nullptr))
            , collator(impl->sortCollator()), m_order(order), m_sortRole(impl->sortRole())
        {
        }
 
        template <typename Item>
        auto operator()(const Item &lhs, const Item &rhs) const
        {
            auto ordering = compare(lhs, rhs);
            return m_order == Qt::AscendingOrder ? ordering < 0 : ordering > 0;
        }
 
        template <typename Item>
        auto compare(const Item &lhs, const Item &rhs) const
        {
            using value_type = QRangeModelDetails::wrapped_t<Item>;
            using multi_role = QRangeModelDetails::is_multi_role<value_type>;
 
            if constexpr (QRangeModelDetails::item_access<value_type>::hasReadRole
                        || multi_role() || has_metaobject<value_type>) {
                QModelRoleData result(m_sortRole);
                // Minor abuse of QModelIndex: the reader needs an index to implement
                // lazy auto-connections, but we only have a column. So we construct
                // an invalid QModelIndex that carries only that column value. That's
                // enough for reading values, and the auto-connection logic skips for
                // invalid indexes.
                ItemReader reader{m_index, result, that};
                Q_ASSERT(!reader.index.isValid());
                reader(lhs);
                const QVariant lhsVariant = std::move(result.data());
                reader(rhs);
                const QVariant rhsVariant = std::move(result.data());
                return QRangeModelImplBase::compareData(lhsVariant, rhsVariant, collator);
            } else if constexpr (std::is_same_v<QVariant, value_type>) {
                return QRangeModelImplBase::compareData(lhs, rhs, collator);
            } else if constexpr (QtOrderingPrivate::CompareThreeWayTester::hasCompareThreeWay_v
                                                                            <value_type, value_type>) {
                // all types supported by QCollator are also three-way comparable
                if constexpr (hasCollatedCompare<value_type>) {
                    if (collator) {
                        using ordering = decltype(qCompareThreeWay(lhs, rhs));
                        int res = collator->compare(lhs, rhs);
                        if (res < 0)
                            return ordering::less;
                        if (res > 0)
                            return ordering::greater;
                        return ordering::equal;
                    }
                }
                return qCompareThreeWay(lhs, rhs);
            } else {
                return unordered{};
            }
        }
 
        bool checkComparable() const
        {
            return that->readAt(that->index(0, 0, {}), [this](const auto &item){
                // before we call std::stable_sort, check that we can compare the
                // types we'll ultimately get called with. This doesn't catch cases
                // where we end up comparing QVariant, and we cannot make this a
                // compile time check as long as readAt etc are not constexpr.
                using ordering = decltype(compare(item, item));
                if constexpr (std::is_same_v<ordering, unordered>) {
#ifndef QT_NO_DEBUG
                    const QMetaType itemtype = QMetaType::fromType<QRangeModelDetails::wrapped_t<
                                                    q20::remove_cvref_t<decltype(item)>>
                                                >();
                    qCritical("QRangeModel: Cannot compare items of type %s in column %d!",
                              itemtype.name(), m_index.column());
#else
                    Q_UNUSED(this);
#endif
                    return false;
                } else {
                    return true;
                }
            });
        }
 
        template <typename Item>
        static std::optional<bool> compareInvalid(const Item &lhs, const Item &rhs)
        {
            // invalid data > valid data
            if (!QRangeModelDetails::isValid(lhs))
                return false;
            if (!QRangeModelDetails::isValid(rhs))
                return true;
            return std::nullopt;
        }
 
        const QRangeModelImpl * const that;
        const QModelIndex m_index;
        const QCollator * const collator;
        const Qt::SortOrder m_order;
        const int m_sortRole;
    };
 
    void sort(int column, Qt::SortOrder order)
    {
        if constexpr (isMutable() && std::is_swappable_v<row_type>) {
            if (rowCount({}) < 2 || column >= columnCount({}))
                return;
            Compare compare(this, column, order);
            if (!compare.checkComparable())
                return;
 
            this->beginLayoutChange();
            QScopeGuard endLayoutChange([this]{ this->endLayoutChange(); });
            that().sortImpl([&compare](const auto &leftRow, const auto &rightRow) {
                if (auto anyInvalid = Compare::compareInvalid(leftRow, rightRow))
                    return *anyInvalid;
                return row_traits::for_element_at(leftRow, compare.m_index.column(),
                                                  [&rightRow, &compare](const auto &leftItem){
                    return row_traits::for_element_at(rightRow, compare.m_index.column(),
                                                      [&leftItem, &compare](const auto &rightItem){
                        // Called by std::stable_sort. Since "column" is a runtime value, we
                        // can't statically assert that lhs and rhs are of the same type.
                        if constexpr (std::is_same_v<decltype(leftItem), decltype(rightItem)>) {
                            if (auto anyInvalid = Compare::compareInvalid(leftItem, rightItem))
                                return *anyInvalid;
                            return compare(QRangeModelDetails::refTo(leftItem),
                                           QRangeModelDetails::refTo(rightItem));
                        } else {
                            Q_UNREACHABLE();
                        }
                        return false;
                    });
                });
            });
        }
    }
 
    template <typename LessThan>
    void sortSubRange(range_type &range, row_ptr expectedParent, const LessThan &lessThan)
    {
        auto begin = QRangeModelDetails::adl_begin(range);
        auto end = QRangeModelDetails::adl_end(range);
        if (begin == end)
            return;
 
        QModelIndexList persistentIndexes = this->persistentIndexList();
        that().prunePersistentIndexList(persistentIndexes, expectedParent);
 
        if (persistentIndexes.isEmpty()) {
            using It = typename range_features::iterator;
            constexpr bool is_random_access = std::is_base_of_v<std::random_access_iterator_tag,
                                                typename std::iterator_traits<It>::iterator_category>;
            // fast path if we have no persistent indexes: sort the range in place
            if constexpr (Compare::hasSortMember) {
                range.sort(lessThan);
                return;
            } else if constexpr (is_random_access) {
                std::stable_sort(begin, end, lessThan);
                return;
            }
        }
 
        // slow path: create an indexed version of the range by adding a
        // column that records row movements.
        struct SortTracker
        {
            row_type row;
            int index;
        };
 
        const int rangeSize = size(range);
        // Allocate all necessary memory here so that a potential exception
        // gets thrown before we have made any modifications.
        std::vector<SortTracker> tracked;
        tracked.reserve(rangeSize);
        std::vector<int> newRows;
        newRows.resize(rangeSize);
 
        // move all rows into that index paired with its unsorted position
        int row = -1;
        for (auto &&it = std::move_iterator(begin); it != std::move_iterator(end); ++it)
            tracked.emplace_back(SortTracker{*it, ++row});
 
        // sort the index based on a comparions of the data
        std::stable_sort(tracked.begin(), tracked.end(),
                            [&lessThan](const SortTracker &lhs, const SortTracker &rhs){
            return lessThan(lhs.row, rhs.row);
        });
 
        // write the values back to the range in (now ordered) sequence,
        // and create a mapping from old to new row
        auto sorted = std::move_iterator(tracked.begin());
        auto write = QRangeModelDetails::adl_begin(range);
        qsizetype changedIndexCount = 0;
        for (int newIndex = 0; newIndex < rangeSize; ++write, ++sorted, ++newIndex) {
            auto &&tracker = *sorted;
            changedIndexCount += (tracker.index != newIndex);
            *write = std::move(tracker.row);
            newRows[tracker.index] = newIndex;
        }
 
        // free memory from intermediate vector
        tracked.clear();
        tracked.shrink_to_fit();
 
        // update relevant persistent model indexes
        for (const auto &fromIndex : std::as_const(persistentIndexes)) {
            const int newRow = newRows.at(fromIndex.row());
            if (fromIndex.row() == newRow)
                continue;
            const QModelIndex toIndex = that().indexImpl(newRow,
                                                         fromIndex.column(),
                                                         fromIndex.parent());
            this->changePersistentIndex(fromIndex, toIndex);
        }
    }
 
    QModelIndexList match(const QModelIndex &start, int role, const QVariant &value, int hits,
                          Qt::MatchFlags flags) const
    {
        QCollator collator = this->matchCollator();
        collator.setCaseSensitivity(flags.testFlag(Qt::MatchCaseSensitive) ? Qt::CaseSensitive
                                                                           : Qt::CaseInsensitive);
        return that().matchImpl(start, role,
                                QRangeModelImplBase::convertMatchValue(value, flags), hits,
                                flags, collator);
    }
 
    bool matchRow(const_row_reference row, const QModelIndex &index, int role, const QVariant &value,
                  Qt::MatchFlags flags, const QCollator &collator) const
    {
        const uint matchType = (flags & Qt::MatchTypeMask).toInt();
 
        return row_traits::for_element_at(row, index.column(), [&](const auto &element) {
            using value_type = q20::remove_cvref_t<decltype(element)>;
            using wrapped_value_type = QRangeModelDetails::wrapped_t<value_type>;
            using multi_role = QRangeModelDetails::is_multi_role<value_type>;
 
            if constexpr (QRangeModelDetails::item_access<wrapped_value_type>::hasReadRole
                          || multi_role() || has_metaobject<value_type>) {
                QModelRoleData roleData(role);
                ItemReader reader{index, roleData, this};
                reader(element);
                return QRangeModelImplBase::matchValue(roleData.data(), value, flags, collator);
            } else if constexpr (std::is_same_v<wrapped_value_type, QVariant>) {
                return QRangeModelImplBase::matchValue(element, value, flags, collator);
            } else {
                constexpr QMetaType mt = QMetaType::fromType<wrapped_value_type>();
                if (mt == value.metaType()) {
                    if (matchType == Qt::MatchExactly)
                        return mt.equals(QRangeModelDetails::pointerTo(element), value.constData());
                    else if constexpr (std::is_same_v<wrapped_value_type, QString>)
                        return QRangeModelImplBase::matchValue(element, value, flags, collator);
                } else {
                    return QRangeModelImplBase::matchValue(QVariant::fromValue(QRangeModelDetails::refTo(element)),
                                                           value, flags, collator);
                }
            }
            return false;
        });
    }
 
    template <typename InsertFn>
    bool doInsertColumns(int column, int count, const QModelIndex &parent, InsertFn insertFn)
    {
        if (count == 0)
            return false;
        range_type * const children = childRange(parent);
        if (!children)
            return false;
 
        this->beginInsertColumns(parent, column, column + count - 1);
 
        for (auto &child : *children) {
            auto it = QRangeModelDetails::pos(child, column);
            (void)insertFn(QRangeModelDetails::refTo(child), it, count);
        }
 
        this->endInsertColumns();
 
        // endInsertColumns emits columnsInserted, at which point clients might
        // have populated the new columns with objects (if the columns aren't objects
        // themselves).
        if constexpr (itemsAreQObjects) {
            if (m_data.context && this->autoConnectPolicy() == AutoConnectPolicy::Full) {
                for (int r = 0; r < that().rowCount(parent); ++r) {
                    for (int c = column; c < column + count; ++c) {
                        const QModelIndex index = that().index(r, c, parent);
                        writeAt(index, [this, &index](QObject *item){
                            return Self::connectProperties(index, item,
                                                           m_data.context, m_data.properties);
                        });
                    }
                }
            }
        }
 
        return true;
    }
 
    bool insertColumns(int column, int count, const QModelIndex &parent)
    {
        if constexpr (dynamicColumns() && isMutable() && row_features::has_insert) {
            return doInsertColumns(column, count, parent, [](auto &row, auto it, int n){
                row.insert(it, n, {});
                return true;
            });
        } else {
            return false;
        }
    }
 
    bool removeColumns(int column, int count, const QModelIndex &parent)
    {
        if constexpr (dynamicColumns() && isMutable() && row_features::has_erase) {
            if (column < 0 || column + count > columnCount(parent))
                return false;
 
            range_type * const children = childRange(parent);
            if (!children)
                return false;
 
            if constexpr (itemsAreQObjects) {
                if (m_data.context && this->autoConnectPolicy() == AutoConnectPolicy::OnRead) {
                    for (int r = 0; r < that().rowCount(parent); ++r) {
                        for (int c = column; c < column + count; ++c) {
                            const QModelIndex index = that().index(r, c, parent);
                            writeAt(index, [this](QObject *item){
                                m_data.connections.removeIf([item](const auto &connection) {
                                    return connection.sender == item;
                                });
                                return true;
                            });
                        }
                    }
                }
            }
 
            this->beginRemoveColumns(parent, column, column + count - 1);
            for (auto &child : *children) {
                const auto start = QRangeModelDetails::pos(child, column);
                QRangeModelDetails::refTo(child).erase(start, std::next(start, count));
            }
            this->endRemoveColumns();
            return true;
        }
        return false;
    }
 
    bool moveColumns(const QModelIndex &sourceParent, int sourceColumn, int count,
                     const QModelIndex &destParent, int destColumn)
    {
        // we only support moving columns within the same parent
        if (sourceParent != destParent)
            return false;
        if constexpr (isMutable() && (row_features::has_rotate || row_features::has_splice)) {
            if (!Structure::canMoveColumns(sourceParent, destParent))
                return false;
 
            if constexpr (dynamicColumns()) {
                // we only support ranges as columns, as other types might
                // not have the same data type across all columns
                range_type * const children = childRange(sourceParent);
                if (!children)
                    return false;
 
                if (!this->beginMoveColumns(sourceParent, sourceColumn, sourceColumn + count - 1,
                                      destParent, destColumn)) {
                    return false;
                }
 
                for (auto &child : *children)
                    QRangeModelDetails::rotate(child, sourceColumn, count, destColumn);
 
                this->endMoveColumns();
                return true;
            }
        }
        return false;
    }
 
    template <typename InsertFn>
    bool doInsertRows(int row, int count, const QModelIndex &parent, InsertFn &&insertFn)
    {
        range_type *children = childRange(parent);
        if (!children)
            return false;
 
        this->beginInsertRows(parent, row, row + count - 1);
 
        row_ptr parentRow = parent.isValid()
                            ? QRangeModelDetails::pointerTo(this->rowData(parent))
                            : nullptr;
        (void)std::forward<InsertFn>(insertFn)(*children, parentRow, row, count);
 
        // fix the parent in all children of the modified row, as the
        // references back to the parent might have become invalid.
        that().resetParentInChildren(children);
 
        this->endInsertRows();
 
        // endInsertRows emits rowsInserted, at which point clients might
        // have populated the new row with objects (if the rows aren't objects
        // themselves).
        if constexpr (itemsAreQObjects || rowsAreQObjects) {
            if (m_data.context && this->autoConnectPolicy() == AutoConnectPolicy::Full) {
                const auto begin = QRangeModelDetails::pos(children, row);
                const auto end = std::next(begin, count);
                int rowIndex = row;
                for (auto it = begin; it != end; ++it, ++rowIndex)
                    autoConnectPropertiesInRow(*it, rowIndex, parent);
            }
        }
 
        return true;
    }
 
    bool insertRows(int row, int count, const QModelIndex &parent)
    {
        if constexpr (canInsertRows()) {
            return doInsertRows(row, count, parent,
                                [this](range_type &children, row_ptr parentRow, int r, int n){
                EmptyRowGenerator generator{0, &that(), parentRow};
 
                const auto pos = QRangeModelDetails::pos(children, r);
                if constexpr (range_features::has_insert_range) {
                    children.insert(pos, std::move(generator), EmptyRowGenerator{n});
                } else if constexpr (rows_are_owning_or_raw_pointers) {
                    auto start = children.insert(pos, n, nullptr); // MSVC doesn't like row_type{}
                    std::copy(std::move(generator), EmptyRowGenerator{n}, start);
                } else {
                    children.insert(pos, n, std::move(*generator));
                }
                return true;
            });
        } else {
            return false;
        }
    }
 
    bool removeRows(int row, int count, const QModelIndex &parent = {})
    {
        if constexpr (canRemoveRows()) {
            const int prevRowCount = rowCount(parent);
            if (row < 0 || row + count > prevRowCount)
                return false;
 
            range_type *children = childRange(parent);
            if (!children)
                return false;
 
            if constexpr (itemsAreQObjects || rowsAreQObjects) {
                if (m_data.context && this->autoConnectPolicy() == AutoConnectPolicy::OnRead) {
                    const auto begin = QRangeModelDetails::pos(children, row);
                    const auto end = std::next(begin, count);
                    int rowIndex = row;
                    for (auto it = begin; it != end; ++it, ++rowIndex)
                        clearConnectionInRow(*it, rowIndex, parent);
                }
            }
 
            this->beginRemoveRows(parent, row, row + count - 1);
            [[maybe_unused]] bool callEndRemoveColumns = false;
            if constexpr (dynamicColumns()) {
                // if we remove the last row in a dynamic model, then we no longer
                // know how many columns we should have, so they will be reported as 0.
                if (prevRowCount == count) {
                    if (const int columns = columnCount(parent)) {
                        callEndRemoveColumns = true;
                        this->beginRemoveColumns(parent, 0, columns - 1);
                    }
                }
            }
            { // erase invalidates iterators
                const auto begin = QRangeModelDetails::pos(children, row);
                const auto end = std::next(begin, count);
                that().deleteRemovedRows(begin, end);
                children->erase(begin, end);
            }
            // fix the parent in all children of the modified row, as the
            // references back to the parent might have become invalid.
            that().resetParentInChildren(children);
 
            if constexpr (dynamicColumns()) {
                if (callEndRemoveColumns) {
                    Q_ASSERT(columnCount(parent) == 0);
                    this->endRemoveColumns();
                }
            }
            this->endRemoveRows();
            return true;
        } else {
            return false;
        }
    }
 
    bool moveRows(const QModelIndex &sourceParent, int sourceRow, int count,
                  const QModelIndex &destParent, int destRow)
    {
        if constexpr (isMutable() && (range_features::has_rotate || range_features::has_splice)) {
            if (!Structure::canMoveRows(sourceParent, destParent))
                return false;
 
            if (sourceParent != destParent) {
                return that().moveRowsAcross(sourceParent, sourceRow, count,
                                             destParent, destRow);
            }
 
            if (sourceRow == destRow || sourceRow == destRow - 1 || count <= 0
             || sourceRow < 0 || sourceRow + count - 1 >= this->rowCount(sourceParent)
             || destRow < 0 || destRow > this->rowCount(destParent)) {
                return false;
            }
 
            range_type *source = childRange(sourceParent);
            // moving within the same range
            if (!this->beginMoveRows(sourceParent, sourceRow, sourceRow + count - 1, destParent, destRow))
                return false;
 
            QRangeModelDetails::rotate(source, sourceRow, count, destRow);
 
            that().resetParentInChildren(source);
 
            this->endMoveRows();
            return true;
        } else {
            return false;
        }
    }
 
    const protocol_type& protocol() const { return QRangeModelDetails::refTo(ProtocolStorage::object()); }
    protocol_type& protocol() { return QRangeModelDetails::refTo(ProtocolStorage::object()); }
 
    QModelIndex parent(const QModelIndex &child) const { return that().parentImpl(child); }
 
    int rowCount(const QModelIndex &parent) const { return that().rowCountImpl(parent); }
 
    static constexpr int fixedColumnCount()
    {
        if constexpr (one_dimensional_range)
            return row_traits::fixed_size();
        else
            return static_column_count;
    }
    int columnCount(const QModelIndex &parent) const { return that().columnCountImpl(parent); }
 
    void destroy() { delete std::addressof(that()); }
 
    Qt::DropActions adjustSupportedDragActions(Qt::DropActions dragActions) {
        if constexpr (!isMutable())
            dragActions &= ~Qt::MoveAction;
        return dragActions;
    }
    Qt::DropActions adjustSupportedDropActions(Qt::DropActions dropActions)
    {
        if constexpr (!isMutable())
            dropActions = Qt::IgnoreAction;
 
        return dropActions;
    }
 
    QStringList mimeTypes() const
    {
        using ItemType = QRangeModelDetails::wrapped_t<typename row_traits::item_type>;
        if constexpr (QRangeModelDetails::item_access<ItemType>::hasMimeTypes)
            return QRangeModelDetails::QRangeModelItemAccess<ItemType>::mimeTypes();
        else if constexpr (QRangeModelDetails::hasMimeTypes<wrapped_row_type>)
            return QRangeModelDetails::QRangeModelRowOptions<wrapped_row_type>::mimeTypes();
        else
            return this->itemModel().QAbstractItemModel::mimeTypes();
    }
 
    bool canDropMimeData(const QMimeData *data, Qt::DropAction action, int row, int column,
                         const QModelIndex &target) const
    {
        if constexpr (isMutable()) {
            bool canDrop;
            using RowOptions = QRangeModelDetails::QRangeModelRowOptions<wrapped_row_type>;
            using ItemType = QRangeModelDetails::wrapped_t<typename row_traits::item_type>;
            using ItemAccess = QRangeModelDetails::QRangeModelItemAccess<ItemType>;
            if constexpr (QRangeModelDetails::item_access<ItemType>::hasCanDropMimeDataFull) {
                canDrop = ItemAccess::canDropMimeData(data, action, row, column, target);
            } else if constexpr (QRangeModelDetails::hasCanDropMimeDataFull<wrapped_row_type>) {
                canDrop = RowOptions::canDropMimeData(data, action, row, column, target);
            } else {
                canDrop = this->itemModel().QAbstractItemModel::canDropMimeData(data, action, row,
                                                                                column, target);
                if constexpr (QRangeModelDetails::item_access<ItemType>::hasCanDropMimeData)
                    canDrop &= ItemAccess::canDropMimeData(data);
                else if constexpr (QRangeModelDetails::hasCanDropMimeData<wrapped_row_type>)
                    canDrop &= RowOptions::canDropMimeData(data);
            }
            return canDrop;
        } else {
            return false;
        }
    }
 
    // orientation == vertical: we drop rows; otherwise we drop individual items
    template <Qt::Orientation orient, typename Entry>
    bool doDropMimeData(std::vector<QRangeModelDetails::DroppedEntry<Entry>> &droppedEntries,
                        DropOperation dropOperation, int row, int column, const QModelIndex &target)
    {
        using DroppedEntry = QRangeModelDetails::DroppedEntry<Entry>;
        using Cell = typename DroppedEntry::Cell;
        if (dropOperation == DropOperation::DontDrop)
            return false;
 
        const bool dropOnTarget = row == -1 && column == -1 && target.isValid();
        const QModelIndex parent = dropOperation == DropOperation::InsertAsChildren
                                 ? target.siblingAtColumn(0) : target.parent();
 
        Cell lastCell;
        if constexpr (orient == Qt::Horizontal)
            lastCell = {0, -1};
        else
            lastCell = {-1, 0};
        int bottomRow = -1;
        int rightColumn = -1;
        // set the target cell for all dropped entries and find the bottom-right
        // cell relative to the drop position
        int maxColumn = that().columnCount(parent) - 1;
        for (auto &droppedEntry : droppedEntries) {
            if (droppedEntry.m_cell == Cell{-1, -1}) {
                if constexpr (orient == Qt::Horizontal) {
                    // auto-inserted items fill all columns before moving to
                    // the next row
                    droppedEntry.m_cell = {lastCell.m_row, lastCell.m_column + 1};
                    if (droppedEntry.m_cell.m_column > maxColumn) {
                        droppedEntry.m_cell.m_column = 0;
                        ++droppedEntry.m_cell.m_row;
                    }
                } else {
                    droppedEntry.m_cell = {lastCell.m_row + 1, lastCell.m_column};
                }
            }
            lastCell = droppedEntry.m_cell;
            bottomRow = std::max(lastCell.m_row, bottomRow);
            rightColumn = std::max(lastCell.m_column, rightColumn);
        }
 
        if (dropOperation == DropOperation::InsertAsChildren) {
            row = rowCount(parent);
            column = 0;
        } else if (dropOnTarget) {
            row = target.row();
            column = target.column();
        } else {
            if (row < 0)
                row = rowCount(parent);
            // dropping into empty space to the right of a table doesn't widen
            if (column < 0)
                column = 0;
        }
        const bool overwrite = dropOperation == DropOperation::OverwriteAndIgnore
                            || dropOperation == DropOperation::OverwriteAndExtend;
 
        // Compute if we need more rows, and try to add them. Abort if that fails.
        const int overwriteRows = overwrite
                                ? std::min(bottomRow + 1, rowCount(parent) - row)
                                : 0;
        const int newRows = dropOperation == DropOperation::OverwriteAndExtend
                          ? bottomRow - overwriteRows + 1
                          : (dropOperation == DropOperation::InsertAsChildren
                             || dropOperation == DropOperation::InsertAsSiblings)
                            ? bottomRow + 1
                            : 0;
        if (newRows > 0 && !insertRows(row, newRows, parent))
            return false;
 
        // Ditto for columns, but InsertAsSiblings/Children only applies to rows
        const int overwriteColumns = overwrite
                                   ? std::min(rightColumn + 1, columnCount(parent) - column)
                                   : 0;
        const int newColumns = dropOperation == DropOperation::OverwriteAndExtend
                             ? rightColumn - overwriteColumns + 1 : 0;
        if (newColumns > 0 && !insertColumns(column, newColumns, parent))
            return false;
 
        // access the target range
        range_type *parentRange = that().childRange(parent);
        if (!parentRange)
            return false;
        range_type &targetRange = *parentRange;
 
        int maxRow = that().rowCount(parent) - 1;
        maxColumn = that().columnCount(parent) - 1;
        auto begin = std::move_iterator(droppedEntries.begin());
        auto end = std::move_iterator(droppedEntries.end());
        for (; begin != end; ++begin) {
            DroppedEntry droppedEntry = *begin;
            const Cell cell = {droppedEntry.m_cell.m_row + row, droppedEntry.m_cell.m_column + column};
            if (cell.m_row > maxRow || cell.m_column > maxColumn) // Ignore
                continue;
            auto writeRow = QRangeModelDetails::pos(targetRange, cell.m_row);
            if constexpr (orient == Qt::Vertical) { // complete rows
                if constexpr (QRangeModelDetails::is_owning_or_raw_pointer<row_type>()) {
                    if (!*writeRow)
                        *writeRow = this->protocol().newRow();
                    **writeRow = std::move(droppedEntry);
                } else {
                    *writeRow = std::move(droppedEntry);
                }
            } else {
                row_traits::for_element_at(*writeRow, cell.m_column, [&](auto &item){
                    using item_type = q20::remove_cvref_t<decltype(item)>;
                    using wrapped_item_type = QRangeModelDetails::wrapped_t<item_type>;
                    if constexpr (QRangeModelDetails::is_any_owning_ptr<item_type>()) {
                        if (!QRangeModelDetails::isValid(item))
                            item.reset(new wrapped_item_type{std::move(droppedEntry)});
                        else
                            *item = std::move(droppedEntry);
                    } else if (!QRangeModelDetails::isValid(item)) {
                        return false;
                    } else {
                        item = std::move(droppedEntry);
                    }
                    return true;
                });
            }
        }
 
        that().resetParentInChildren(&targetRange);
 
        const QModelIndex topLeft = index(row, column, parent);
        const QModelIndex bottomRight = orient == Qt::Horizontal
                                      ? sibling(row + bottomRow, column + rightColumn, topLeft)
                                      : sibling(row + bottomRow, maxColumn, topLeft);
        this->dataChanged(topLeft, bottomRight, {});
 
        return true;
    }
 
    bool dropMimeData(const QMimeData *data, Qt::DropAction action, int row, int column,
                      const QModelIndex &target)
    {
        if constexpr (isMutable()) {
            if (!canDropMimeData(data, action, row, column, target))
                return false;
 
            const bool dropOnTarget = row == -1 && column == -1 && target.isValid();
 
            auto automaticDropOption = [=](auto dropResult){
                DropOperation dropOperation;
                if constexpr (std::is_same_v<bool, decltype(dropResult)>) {
                    dropOperation = dropResult ? DropOperation::Automatic
                                               : DropOperation::DontDrop;
                } else { // it's a QRangeModel::DropOperation
                    dropOperation = static_cast<DropOperation>(dropResult);
                }
 
                if (dropOperation == DropOperation::Automatic) {
                    if constexpr (!canInsertRows())
                        dropOperation = DropOperation::OverwriteAndIgnore;
                    else if (!dropOnTarget)
                        dropOperation = DropOperation::InsertAsSiblings;
                    else if (target.siblingAtColumn(0).flags().testFlag(Qt::ItemNeverHasChildren))
                        dropOperation = DropOperation::OverwriteAndExtend;
                    else
                        dropOperation = DropOperation::InsertAsChildren;
                }
                return dropOperation;
            };
 
            using ItemType = QRangeModelDetails::wrapped_t<typename row_traits::item_type>;
            if constexpr (QRangeModelDetails::item_access<ItemType>::hasDropMimeDataFull
                       || QRangeModelDetails::item_access<ItemType>::hasDropMimeData) {
                using ItemAccess = QRangeModelDetails::QRangeModelItemAccess<ItemType>;
                using DroppedItem = QRangeModelDetails::DroppedEntry<ItemType>;
                std::vector<DroppedItem> droppedItems;
                DropOperation dropOperation = automaticDropOption([&]{
                    auto inserter = std::back_inserter(droppedItems);
                    if constexpr (QRangeModelDetails::item_access<ItemType>::hasDropMimeDataFull)
                        return ItemAccess::dropMimeData(data, action, row, column, target, inserter);
                    else
                        return ItemAccess::dropMimeData(data, inserter);
                }());
                if (doDropMimeData<Qt::Horizontal>(droppedItems, dropOperation, row, column, target))
                    return true;
                // fall through to try the default mime type
            } else if constexpr (QRangeModelDetails::hasDropMimeDataFull<wrapped_row_type>
                              || QRangeModelDetails::hasDropMimeData<wrapped_row_type>) {
                using RowOptions = QRangeModelDetails::QRangeModelRowOptions<wrapped_row_type>;
                using DroppedRow = QRangeModelDetails::DroppedEntry<wrapped_row_type>;
                std::vector<DroppedRow> droppedRows;
                DropOperation dropOperation = automaticDropOption([&]{
                    auto inserter = std::back_inserter(droppedRows);
                    if constexpr (QRangeModelDetails::hasDropMimeDataFull<wrapped_row_type>)
                        return RowOptions::dropMimeData(data, action, row, column, target, inserter);
                    else
                        return RowOptions::dropMimeData(data, inserter);
                }());
                if (doDropMimeData<Qt::Vertical>(droppedRows, dropOperation, row, column, target))
                    return true;
            }
            // default mime type handling: dropping on item -> try to set the data
            if (dropOnTarget && that().dropOnItem(data, target))
                return true;
        }
        return false;
    }
 
    // A bidirectional-iterator that, given a list of QModelIndex, dereferences
    // to a list of rows or items, plus QModelIndex, without copying any data.
    // For segments in indexes covering full rows, we skip over the individual
    // indexes and give the dereferenced index a column value of -1.
    struct MimeDataRowIterator
    {
        using base_iterator = QModelIndexList::const_iterator;
        using difference_type = typename base_iterator::difference_type;
        using iterator_category = std::bidirectional_iterator_tag;
        using value_type = QRangeModelDetails::MimeDataEntry<const_row_reference>;
        using reference [[maybe_unused]] = value_type;
        using const_reference = value_type;
        using pointer [[maybe_unused]] = void;
 
        MimeDataRowIterator() = default;
        MimeDataRowIterator(base_iterator it, base_iterator begin, base_iterator end,
                            const QRangeModelImpl *model)
            : m_it(it), m_begin(begin), m_end(end), m_model(model)
            , m_columnCount(model->columnCount({}))
        {
            updateCurrentIndexFullRow();
        }
 
        const_reference operator*() const
        {
            const QModelIndex &index = *m_it;
            return {m_model->rowData(index),
                    m_currentIndexIsFullRow
                    ? m_model->createIndex(m_it->row(), -1, m_it->internalPointer()) : index};
        }
 
        MimeDataRowIterator &operator++() {
            if (m_currentIndexIsFullRow)
                m_it += m_columnCount;
            else
                ++m_it;
            updateCurrentIndexFullRow();
            return *this;
        }
        MimeDataRowIterator operator++(int) { auto tmp = *this; ++(*this); return tmp; }
 
        MimeDataRowIterator &operator--() {
            --m_it;
            m_currentIndexIsFullRow = false;
            const int lastColumn = m_columnCount - 1;
            if (m_it - m_begin >= lastColumn && m_it->column() == lastColumn) {
                const QModelIndex &firstInRow = m_it[-lastColumn];
                if (m_it->row() == firstInRow.row()
                 && firstInRow.internalPointer() == m_it->internalPointer()) {
                    m_currentIndexIsFullRow = true;
                    m_it -= lastColumn;
                }
            }
            return *this;
        }
        MimeDataRowIterator operator--(int) { auto tmp = *this; --(*this); return tmp; }
 
        MimeDataRowIterator operator-(difference_type n) const
        {
            auto tmp = *this; tmp.m_it -= n; return tmp;
        }
 
        bool operator==(const MimeDataRowIterator &other) const { return m_it == other.m_it; }
        bool operator!=(const MimeDataRowIterator &other) const { return m_it != other.m_it; }
 
    private:
        void updateCurrentIndexFullRow()
        {
            m_currentIndexIsFullRow = false;
            if (m_it == m_end || m_it->column() || m_end - m_it < m_columnCount)
                return;
            const QModelIndex &lastInRow = m_it[m_columnCount - 1];
            m_currentIndexIsFullRow = lastInRow.row() == m_it->row()
                                   && lastInRow.internalPointer() == m_it->internalPointer();
        }
 
        base_iterator m_it;
        base_iterator m_begin;
        base_iterator m_end;
        const QRangeModelImpl *m_model;
        int m_columnCount = 0;
        bool m_currentIndexIsFullRow = false;
    };
 
    struct MimeDataItemIterator
    {
        using base_iterator = QModelIndexList::const_iterator;
        // row_traits::item_type is wrapped, and void if not the same for all columns
        using item_type = std::conditional_t<std::is_void_v<typename row_traits::item_type>,
                                            void *, typename row_traits::item_type>;
        using difference_type = typename base_iterator::difference_type;
        using iterator_category = std::bidirectional_iterator_tag;
        using value_type = QRangeModelDetails::MimeDataEntry<item_type>;
        using reference [[maybe_unused]] = value_type;
        using const_reference  = value_type;
        using pointer [[maybe_unused]] = void;
 
        const_reference operator*() const
        {
            const QModelIndex &index = *m_it;
            // pointer to the item as stored, including wrapping
            const item_type *pitem = nullptr;
            const auto &row = m_model->rowData(index);
            if (QRangeModelDetails::isValid(row)) {
                row_traits::for_element_at(QRangeModelDetails::refTo(row), index.column(),
                                           [&pitem](const auto &item){
                    pitem = &item;
                    return true;
                });
            }
            if constexpr (std::disjunction_v<QRangeModelDetails::is_owning_or_raw_pointer<row_type>,
                                             QRangeModelDetails::is_owning_or_raw_pointer<item_type>>) {
                if (Q_UNLIKELY(!QRangeModelDetails::isValid(pitem))) {
                    // no use in warning about invalid item here, as the user
                    // can't check for validity without dereferencing the iterator.
                    constexpr bool is_constexpr_default_constructible_v =
                        value_type::template is_constexpr_default_constructible<item_type>::value;
                    if constexpr (is_constexpr_default_constructible_v) {
                        Q_CONSTINIT static const item_type emptyDefault;
                        return {emptyDefault, index};
                    } else {
                        // known to cause runtime initialization
                        static const item_type emptyDefault;
                        return {emptyDefault, index};
                    }
                }
            }
            // this will decompose to a [wrapped_item_type, QModelIndex]
            return {*pitem, index};
        }
        MimeDataItemIterator &operator++() { ++m_it; return *this; }
        MimeDataItemIterator operator++(int) { auto tmp = *this; ++(*this); return tmp; }
 
        MimeDataItemIterator &operator--() { --m_it; return *this; }
        MimeDataItemIterator operator--(int) { auto tmp = *this; --(*this); return tmp; }
 
        MimeDataItemIterator operator-(difference_type n) const
        {
            auto tmp = *this; tmp.m_it -= n; return tmp;
        }
 
        bool operator==(const MimeDataItemIterator &other) const { return m_it == other.m_it; }
        bool operator!=(const MimeDataItemIterator &other) const { return m_it != other.m_it; }
 
        base_iterator m_it;
        const QRangeModelImpl *m_model;
    };
 
    template <typename Iterator>
    struct MimeDataRange {
        Iterator begin() const { return m_begin; }
        Iterator end() const { return m_end; }
        auto rbegin() const { return std::reverse_iterator(m_end); }
        auto rend() const { return std::reverse_iterator(m_begin); }
        auto first() const { return *m_begin;}
        auto last() const { return *(m_end - 1);}
        bool isEmpty() const { return m_begin == m_end; }
        bool empty() const { return m_begin == m_end; }
        Iterator m_begin;
        Iterator m_end;
    };
 
    QMimeData *mimeData(const QModelIndexList &indexes) const
    {
        QMimeData *result = nullptr;
        using RowOptions = QRangeModelDetails::QRangeModelRowOptions<wrapped_row_type>;
        using ItemType = QRangeModelDetails::wrapped_t<typename row_traits::item_type>;
 
        if constexpr (QRangeModelDetails::item_access<ItemType>::hasMimeData) {
            using ItemAccess = QRangeModelDetails::QRangeModelItemAccess<ItemType>;
            const auto begin = MimeDataItemIterator{indexes.begin(), this};
            const auto end = MimeDataItemIterator{indexes.end(), this};
            result = ItemAccess::mimeData(MimeDataRange<MimeDataItemIterator>{begin, end});
        } else if constexpr (QRangeModelDetails::hasMimeDataRowSpan<wrapped_row_type>) {
            const auto begin = MimeDataRowIterator(indexes.begin(), indexes.begin(), indexes.end(), this);
            const auto end = MimeDataRowIterator(indexes.end(), indexes.begin(), indexes.end(), this);
            result = RowOptions::mimeData(MimeDataRange<MimeDataRowIterator>{begin, end});
        } else if constexpr (QRangeModelDetails::hasMimeDataIndexList<wrapped_row_type>) {
            result = RowOptions::mimeData(indexes);
        }
 
        return result;
    }
 
    template <typename BaseMethod, typename BaseMethod::template Overridden<Self> overridden>
    using Override = typename Ancestor::template Override<BaseMethod, overridden>;
 
    using Destroy = Override<QRangeModelImplBase::Destroy, &Self::destroy>;
    using Index = Override<QRangeModelImplBase::Index, &Self::index>;
    using Parent = Override<QRangeModelImplBase::Parent, &Self::parent>;
    using Sibling = Override<QRangeModelImplBase::Sibling, &Self::sibling>;
    using RowCount = Override<QRangeModelImplBase::RowCount, &Self::rowCount>;
    using ColumnCount = Override<QRangeModelImplBase::ColumnCount, &Self::columnCount>;
    using Flags = Override<QRangeModelImplBase::Flags, &Self::flags>;
    using HeaderData = Override<QRangeModelImplBase::HeaderData, &Self::headerData>;
 
    using Data = Override<QRangeModelImplBase::Data, &Self::data>;
    using ItemData = Override<QRangeModelImplBase::ItemData, &Self::itemData>;
    using RoleNames = Override<QRangeModelImplBase::RoleNames, &Self::roleNames>;
    using InvalidateCaches = Override<QRangeModelImplBase::InvalidateCaches, &Self::invalidateCaches>;
    using SetHeaderData = Override<QRangeModelImplBase::SetHeaderData, &Self::setHeaderData>;
    using SetData = Override<QRangeModelImplBase::SetData, &Self::setData>;
    using SetItemData = Override<QRangeModelImplBase::SetItemData, &Self::setItemData>;
    using ClearItemData = Override<QRangeModelImplBase::ClearItemData, &Self::clearItemData>;
    using InsertColumns = Override<QRangeModelImplBase::InsertColumns, &Self::insertColumns>;
    using RemoveColumns = Override<QRangeModelImplBase::RemoveColumns, &Self::removeColumns>;
    using MoveColumns = Override<QRangeModelImplBase::MoveColumns, &Self::moveColumns>;
    using InsertRows = Override<QRangeModelImplBase::InsertRows, &Self::insertRows>;
    using RemoveRows = Override<QRangeModelImplBase::RemoveRows, &Self::removeRows>;
    using MoveRows = Override<QRangeModelImplBase::MoveRows, &Self::moveRows>;
 
    using MultiData = Override<QRangeModelImplBase::MultiData, &Self::multiData>;
    using SetAutoConnectPolicy = Override<QRangeModelImplBase::SetAutoConnectPolicy,
                                          &Self::setAutoConnectPolicy>;
 
    using InterfaceVersion = Override<QRangeModelImplBase::InterfaceVersion, &Self::interfaceVersion>;
    using Sort = Override<QRangeModelImplBase::Sort, &Self::sort>;
    using Match = Override<QRangeModelImplBase::Match, &Self::match>;
    using AdjustSupportedDragActions = Override<QRangeModelImplBase::AdjustSupportedDragActions,
                                                &Self::adjustSupportedDragActions>;
    using AdjustSupportedDropActions = Override<QRangeModelImplBase::AdjustSupportedDropActions,
                                                &Self::adjustSupportedDropActions>;
 
    using MimeTypes = Override<QRangeModelImplBase::MimeTypes, &Self::mimeTypes>;
    using CanDropMimeData = Override<QRangeModelImplBase::CanDropMimeData, &Self::canDropMimeData>;
    using DropMimeData = Override<QRangeModelImplBase::DropMimeData, &Self::dropMimeData>;
    using MimeData = Override<QRangeModelImplBase::MimeData, &Self::mimeData>;
 
protected:
    ~QRangeModelImpl()
    {
        deleteOwnedRows();
    }
 
    void deleteOwnedRows()
    {
        // We delete row objects if we are not operating on a reference or pointer
        // to a range, as in that case, the owner of the referenced/pointed to
        // range also owns the row entries.
        // ### Problem: if we get a copy of a range (no matter if shared or not),
        // then adding rows will create row objects in the model's copy, and the
        // client can never delete those. But copied rows will be the same pointer,
        // which we must not delete (as we didn't create them).
 
        static constexpr bool modelCopied = !QRangeModelDetails::is_wrapped<Range>() &&
                (std::is_reference_v<Range> || std::is_const_v<std::remove_reference_t<Range>>);
 
        static constexpr bool modelShared = QRangeModelDetails::is_any_shared_ptr<Range>();
 
        static constexpr bool default_row_deleter = protocol_traits::is_default &&
                protocol_traits::has_deleteRow;
 
        static constexpr bool ambiguousRowOwnership = (modelCopied || modelShared) &&
                rows_are_raw_pointers && default_row_deleter;
 
        static_assert(!ambiguousRowOwnership,
                "Using of copied and shared tree and table models with rows as raw pointers, "
                "and the default protocol is not allowed due to ambiguity of rows ownership. "
                "Move the model in, use another row type, or implement a custom tree protocol.");
 
        if constexpr (protocol_traits::has_deleteRow && !std::is_pointer_v<Range>
                   && !QRangeModelDetails::is_any_of<Range, std::reference_wrapper>()) {
            const auto begin = QRangeModelDetails::adl_begin(*m_data.model());
            const auto end = QRangeModelDetails::adl_end(*m_data.model());
            that().deleteRemovedRows(begin, end);
        }
    }
 
    static constexpr bool canInsertRows()
    {
        if constexpr (dynamicColumns() && !row_features::has_resize) {
            // If we operate on dynamic columns and cannot resize a newly
            // constructed row, then we cannot insert.
            return false;
        } else if constexpr (!protocol_traits::has_newRow) {
            // We also cannot insert if we cannot create a new row element
            return false;
        } else if constexpr (!range_features::has_insert_range
                          && !std::is_copy_constructible_v<row_type>) {
            // And if the row is a move-only type, then the range needs to be
            // backed by a container that can move-insert default-constructed
            // row elements.
            return false;
        } else {
            return Structure::canInsertRowsImpl();
        }
    }
 
    static constexpr bool canRemoveRows()
    {
        return Structure::canRemoveRowsImpl();
    }
 
    template <typename F>
    bool writeAt(const QModelIndex &index, F&& writer)
    {
        row_reference row = rowData(index);
        if (!QRangeModelDetails::isValid(row))
            return false;
        return row_traits::for_element_at(row, index.column(), [&writer](auto &&target) {
            using target_type = decltype(target);
            // we can only assign to an lvalue reference
            if constexpr (std::is_lvalue_reference_v<target_type>
                        && !std::is_const_v<std::remove_reference_t<target_type>>) {
                return writer(std::forward<target_type>(target));
            } else {
                return false;
            }
        });
    }
 
    template <typename F>
    bool readAt(const QModelIndex &index, F&& reader) const {
        const_row_reference row = rowData(index);
        if (!QRangeModelDetails::isValid(row))
            return false;
        return row_traits::for_element_at(row, index.column(), std::forward<F>(reader));
    }
 
    template <typename Value>
    static QVariant read(const Value &value)
    {
        if constexpr (std::is_constructible_v<QVariant, Value>)
            return QVariant(value);
        else
            return QVariant::fromValue(value);
    }
    template <typename Value>
    static QVariant read(Value *value)
    {
        if (value) {
            if constexpr (std::is_constructible_v<QVariant, Value *>)
                return QVariant(value);
            else
                return read(*value);
        }
        return {};
    }
 
    template <typename Target>
    static bool write(Target &target, const QVariant &value)
    {
        using Type = std::remove_reference_t<Target>;
        if constexpr (std::is_constructible_v<Target, QVariant>) {
            target = value;
            return true;
        } else if (value.canConvert<Type>()) {
            target = value.value<Type>();
            return true;
        }
        return false;
    }
    template <typename Target>
    static bool write(Target *target, const QVariant &value)
    {
        if (target)
            return write(*target, value);
        return false;
    }
 
    template <typename ItemType>
    QMetaProperty roleProperty(int role) const
    {
        struct {
            operator QMetaProperty() const {
                const QByteArray roleName = that.itemModel().roleNames().value(role);
                const QMetaObject &mo = ItemType::staticMetaObject;
                if (const int index = mo.indexOfProperty(roleName.data());
                    index >= 0) {
                    return mo.property(index);
                }
                return {};
            }
            const QRangeModelImpl &that;
            const int role;
        } findProperty{*this, role};
 
        if constexpr (ModelData::cachesProperties)
            return *m_data.properties.tryEmplace(role, findProperty).iterator;
        else
            return findProperty;
    }
 
    void connectPropertyOnRead(const QModelIndex &index, int role,
                               const QObject *gadget, const QMetaProperty &prop) const
    {
        if (!index.isValid())
            return;
        const typename ModelData::Connection connection = {gadget, role};
        if (prop.hasNotifySignal() && this->autoConnectPolicy() == AutoConnectPolicy::OnRead
                                   && !m_data.connections.contains(connection)) {
            if constexpr (isMutable())
                Self::connectProperty(index, gadget, m_data.context, role, prop);
            else
                Self::connectPropertyConst(index, gadget, m_data.context, role, prop);
            m_data.connections.insert(connection);
        }
    }
 
    template <typename ItemType>
    QVariant readRole(const QModelIndex &index, int role, ItemType *gadget) const
    {
        using item_type = std::remove_pointer_t<ItemType>;
        QVariant result;
        QMetaProperty prop = roleProperty<item_type>(role);
        if (!prop.isValid() && role == Qt::EditRole) {
            role = Qt::DisplayRole;
            prop = roleProperty<item_type>(Qt::DisplayRole);
        }
 
        if (prop.isValid()) {
            if constexpr (itemsAreQObjects)
                connectPropertyOnRead(index, role, gadget, prop);
            result = readProperty(prop, gadget);
        }
        return result;
    }
 
    template <typename ItemType>
    QVariant readRole(const QModelIndex &index, int role, const ItemType &gadget) const
    {
        return readRole(index, role, &gadget);
    }
 
    template <typename ItemType>
    static QVariant readProperty(const QMetaProperty &prop, ItemType *gadget)
    {
        if constexpr (std::is_base_of_v<QObject, ItemType>)
            return prop.read(gadget);
        else
            return prop.readOnGadget(gadget);
    }
 
    template <typename ItemType>
    QVariant readProperty(const QModelIndex &index, ItemType *gadget) const
    {
        using item_type = std::remove_pointer_t<ItemType>;
        const QMetaObject &mo = item_type::staticMetaObject;
        const QMetaProperty prop = mo.property(index.column() + mo.propertyOffset());
 
        if constexpr (rowsAreQObjects)
            connectPropertyOnRead(index, Qt::DisplayRole, gadget, prop);
 
        return readProperty(prop, gadget);
    }
 
    template <typename ItemType>
    QVariant readProperty(const QModelIndex &index, const ItemType &gadget) const
    {
        return readProperty(index, &gadget);
    }
 
    template <typename ItemType>
    bool writeRole(int role, ItemType *gadget, const QVariant &data)
    {
        using item_type = std::remove_pointer_t<ItemType>;
        auto prop = roleProperty<item_type>(role);
        if (!prop.isValid() && role == Qt::EditRole)
            prop = roleProperty<item_type>(Qt::DisplayRole);
 
        return prop.isValid() ? writeProperty(prop, gadget, data) : false;
    }
 
    template <typename ItemType>
    bool writeRole(int role, ItemType &&gadget, const QVariant &data)
    {
        return writeRole(role, &gadget, data);
    }
 
    template <typename ItemType>
    static bool writeProperty(const QMetaProperty &prop, ItemType *gadget, const QVariant &data)
    {
        if constexpr (std::is_base_of_v<QObject, ItemType>)
            return prop.write(gadget, data);
        else
            return prop.writeOnGadget(gadget, data);
    }
    template <typename ItemType>
    static bool writeProperty(int property, ItemType *gadget, const QVariant &data)
    {
        using item_type = std::remove_pointer_t<ItemType>;
        const QMetaObject &mo = item_type::staticMetaObject;
        return writeProperty(mo.property(property + mo.propertyOffset()), gadget, data);
    }
 
    template <typename ItemType>
    static bool writeProperty(int property, ItemType &&gadget, const QVariant &data)
    {
        return writeProperty(property, &gadget, data);
    }
 
    template <typename ItemType>
    static bool resetProperty(int property, ItemType *object)
    {
        using item_type = std::remove_pointer_t<ItemType>;
        const QMetaObject &mo = item_type::staticMetaObject;
        bool success = true;
        if (property == -1) {
            // reset all properties
            if constexpr (std::is_base_of_v<QObject, item_type>) {
                for (int p = mo.propertyOffset(); p < mo.propertyCount(); ++p)
                    success = writeProperty(mo.property(p), object, {}) && success;
            } else { // reset a gadget by assigning a default-constructed
                *object = {};
            }
        } else {
            success = writeProperty(mo.property(property + mo.propertyOffset()), object, {});
        }
        return success;
    }
 
    template <typename ItemType>
    static bool resetProperty(int property, ItemType &&object)
    {
        return resetProperty(property, &object);
    }
 
    // helpers
    const_row_reference rowData(const QModelIndex &index) const
    {
        Q_ASSERT(index.isValid());
        return that().rowDataImpl(index);
    }
 
    row_reference rowData(const QModelIndex &index)
    {
        Q_ASSERT(index.isValid());
        return that().rowDataImpl(index);
    }
 
    const range_type *childRange(const QModelIndex &index) const
    {
        if (!index.isValid())
            return m_data.model();
        if (index.column()) // only items at column 0 can have children
            return nullptr;
        return that().childRangeImpl(index);
    }
 
    range_type *childRange(const QModelIndex &index)
    {
        if (!index.isValid())
            return m_data.model();
        if (index.column()) // only items at column 0 can have children
            return nullptr;
        return that().childRangeImpl(index);
    }
 
    template <typename, typename, typename> friend class QRangeModelAdapter;
 
    ModelData m_data;
};
 
// Implementations that depends on the model structure (flat vs tree) that will
// be specialized based on a protocol type. The main template implements tree
// support through a protocol type.
template <typename Range, typename Protocol>
class QGenericTreeItemModelImpl
    : public QRangeModelImpl<QGenericTreeItemModelImpl<Range, Protocol>, Range, Protocol>
{
    using Base = QRangeModelImpl<QGenericTreeItemModelImpl<Range, Protocol>, Range, Protocol>;
    friend class QRangeModelImpl<QGenericTreeItemModelImpl<Range, Protocol>, Range, Protocol>;
 
    using range_type = typename Base::range_type;
    using range_features = typename Base::range_features;
    using row_type = typename Base::row_type;
    using row_ptr = typename Base::row_ptr;
    using const_row_ptr = typename Base::const_row_ptr;
 
    using tree_traits = typename Base::protocol_traits;
    static constexpr bool is_mutable_impl = tree_traits::has_mutable_childRows;
 
    static constexpr bool rows_are_any_refs_or_pointers = Base::rows_are_raw_pointers ||
                                 QRangeModelDetails::is_smart_ptr<row_type>() ||
                                 QRangeModelDetails::is_any_of<row_type, std::reference_wrapper>();
    static_assert(!Base::dynamicColumns(), "A tree must have a static number of columns!");
 
public:
    QGenericTreeItemModelImpl(Range &&model, Protocol &&p, QRangeModel *itemModel)
        : Base(std::forward<Range>(model), std::forward<Protocol>(p), itemModel)
    {};
 
    void setParentRow(range_type &children, row_ptr parent)
    {
        for (auto &&child : children)
            this->protocol().setParentRow(QRangeModelDetails::refTo(child), parent);
        resetParentInChildren(&children);
    }
 
    void deleteRemovedRows(range_type &range)
    {
        deleteRemovedRows(QRangeModelDetails::adl_begin(range), QRangeModelDetails::adl_end(range));
    }
 
    bool autoConnectProperties(const QModelIndex &parent) const
    {
        auto *children = this->childRange(parent);
        if (!children)
            return true;
        return autoConnectPropertiesRange(QRangeModelDetails::refTo(children), parent);
    }
 
protected:
    QModelIndex indexImpl(int row, int column, const QModelIndex &parent) const
    {
        if (!parent.isValid())
            return this->createIndex(row, column);
        // only items at column 0 can have children
        if (parent.column())
            return QModelIndex();
 
        const_row_ptr grandParent = static_cast<const_row_ptr>(parent.constInternalPointer());
        const auto &parentSiblings = childrenOf(grandParent);
        const auto it = QRangeModelDetails::pos(parentSiblings, parent.row());
        return this->createIndex(row, column, QRangeModelDetails::pointerTo(*it));
    }
 
    QModelIndex parentImpl(const QModelIndex &child) const
    {
        if (!child.isValid())
            return {};
 
        // no pointer to parent row - no parent
        const_row_ptr parentRow = static_cast<const_row_ptr>(child.constInternalPointer());
        if (!parentRow)
            return {};
 
        // get the siblings of the parent via the grand parent
        auto &&grandParent = this->protocol().parentRow(QRangeModelDetails::refTo(parentRow));
        const range_type &parentSiblings = childrenOf(QRangeModelDetails::pointerTo(grandParent));
        // find the index of parentRow
        const auto begin = QRangeModelDetails::adl_begin(parentSiblings);
        const auto end = QRangeModelDetails::adl_end(parentSiblings);
        const auto it = std::find_if(begin, end, [parentRow](auto &&s){
            return QRangeModelDetails::pointerTo(std::forward<decltype(s)>(s)) == parentRow;
        });
        if (it != end)
            return this->createIndex(std::distance(begin, it), 0,
                                     QRangeModelDetails::pointerTo(grandParent));
        return {};
    }
 
    int rowCountImpl(const QModelIndex &parent) const
    {
        return Base::size(this->childRange(parent));
    }
 
    int columnCountImpl(const QModelIndex &) const
    {
        // All levels of a tree have to have the same, fixed, column count.
        // If static_column_count is -1 for a tree, static assert fires
        return Base::fixedColumnCount();
    }
 
    static constexpr Qt::ItemFlags defaultFlags()
    {
        return Qt::ItemIsEnabled | Qt::ItemIsSelectable;
    }
 
    static constexpr bool canInsertRowsImpl()
    {
        // We must not insert rows if we cannot adjust the parents of the
        // children of the following rows. We don't have to do that if the
        // range operates on pointers.
        return (rows_are_any_refs_or_pointers || tree_traits::has_setParentRow)
             && Base::dynamicRows() && range_features::has_insert;
    }
 
    static constexpr bool canRemoveRowsImpl()
    {
        // We must not remove rows if we cannot adjust the parents of the
        // children of the following rows. We don't have to do that if the
        // range operates on pointers.
        return (rows_are_any_refs_or_pointers || tree_traits::has_setParentRow)
             && Base::dynamicRows() && range_features::has_erase;
    }
 
    static constexpr bool canMoveColumns(const QModelIndex &, const QModelIndex &)
    {
        return true;
    }
 
    static constexpr bool canMoveRows(const QModelIndex &, const QModelIndex &)
    {
        return true;
    }
 
    bool moveRowsAcross(const QModelIndex &sourceParent, int sourceRow, int count,
                        const QModelIndex &destParent, int destRow)
    {
        // If rows are pointers, then reference to the parent row don't
        // change, so we can move them around freely. Otherwise we need to
        // be able to explicitly update the parent pointer.
        if constexpr (!rows_are_any_refs_or_pointers && !tree_traits::has_setParentRow) {
            return false;
        } else if constexpr (!(range_features::has_insert && range_features::has_erase)) {
            return false;
        } else if (!this->beginMoveRows(sourceParent, sourceRow, sourceRow + count - 1,
                                        destParent, destRow)) {
            return false;
        }
 
        range_type *source = this->childRange(sourceParent);
        range_type *destination = this->childRange(destParent);
 
        // If we can insert data from another range into, then
        // use that to move the old data over.
        const auto destStart = QRangeModelDetails::pos(destination, destRow);
        if constexpr (range_features::has_insert_range) {
            const auto sourceStart = QRangeModelDetails::pos(*source, sourceRow);
            const auto sourceEnd = std::next(sourceStart, count);
 
            destination->insert(destStart, std::move_iterator(sourceStart),
                                           std::move_iterator(sourceEnd));
        } else if constexpr (std::is_copy_constructible_v<row_type>) {
            // otherwise we have to make space first, and copy later.
            destination->insert(destStart, count, row_type{});
        }
 
        row_ptr parentRow = destParent.isValid()
                          ? QRangeModelDetails::pointerTo(this->rowData(destParent))
                          : nullptr;
 
        // if the source's parent was already inside the new parent row,
        // then the source row might have become invalid, so reset it.
        if (parentRow == static_cast<row_ptr>(sourceParent.internalPointer())) {
            if (sourceParent.row() < destRow) {
                source = this->childRange(sourceParent);
            } else {
                // the source parent moved down within destination
                source = this->childRange(this->createIndex(sourceParent.row() + count, 0,
                                                            sourceParent.internalPointer()));
            }
        }
 
        // move the data over and update the parent pointer
        {
            const auto writeStart = QRangeModelDetails::pos(destination, destRow);
            const auto writeEnd = std::next(writeStart, count);
            const auto sourceStart = QRangeModelDetails::pos(source, sourceRow);
            const auto sourceEnd = std::next(sourceStart, count);
 
            for (auto write = writeStart, read = sourceStart; write != writeEnd; ++write, ++read) {
                // move data over if not already done, otherwise
                // only fix the parent pointer
                if constexpr (!range_features::has_insert_range)
                    *write = std::move(*read);
                this->protocol().setParentRow(QRangeModelDetails::refTo(*write), parentRow);
            }
            // remove the old rows from the source parent
            source->erase(sourceStart, sourceEnd);
        }
 
        // Fix the parent pointers in children of both source and destination
        // ranges, as the references to the entries might have become invalid.
        // We don't have to do that if the rows are pointers, as in that case
        // the references to the entries are stable.
        resetParentInChildren(destination);
        resetParentInChildren(source);
 
        this->endMoveRows();
        return true;
    }
 
    auto makeEmptyRow(row_ptr parentRow)
    {
        // tree traversal protocol: if we are here, then it must be possible
        // to change the parent of a row.
        static_assert(tree_traits::has_setParentRow);
        row_type empty_row = this->protocol().newRow();
        if (QRangeModelDetails::isValid(empty_row) && parentRow)
            this->protocol().setParentRow(QRangeModelDetails::refTo(empty_row), parentRow);
        return empty_row;
    }
 
    template <typename It, typename Sentinel>
    void deleteRemovedRows(It &&begin, Sentinel &&end)
    {
        if constexpr (tree_traits::has_deleteRow) {
            for (auto it = begin; it != end; ++it) {
                if constexpr (Base::isMutable()) {
                    decltype(auto) children = this->protocol().childRows(QRangeModelDetails::refTo(*it));
                    if (QRangeModelDetails::isValid(children)) {
                        deleteRemovedRows(QRangeModelDetails::adl_begin(children),
                                          QRangeModelDetails::adl_end(children));
                        QRangeModelDetails::refTo(children) = range_type{ };
                    }
                }
 
                this->protocol().deleteRow(std::move(*it));
            }
        }
    }
 
    void resetParentInChildren(range_type *children)
    {
        const auto persistentIndexList = this->persistentIndexList();
        const auto [firstColumn, lastColumn] = [&persistentIndexList]{
            int first = std::numeric_limits<int>::max();
            int last = -1;
            for (const auto &pmi : persistentIndexList) {
                first = (std::min)(pmi.column(), first);
                last = (std::max)(pmi.column(), last);
            }
            return std::pair(first, last);
        }();
 
        resetParentInChildrenRecursive(children, firstColumn, lastColumn);
    }
 
    void resetParentInChildrenRecursive(range_type *children, int pmiFromColumn, int pmiToColumn)
    {
        if constexpr (tree_traits::has_setParentRow && !rows_are_any_refs_or_pointers) {
            const bool changePersistentIndexes = pmiToColumn >= pmiFromColumn;
            const auto begin = QRangeModelDetails::adl_begin(*children);
            const auto end = QRangeModelDetails::adl_end(*children);
            for (auto it = begin; it != end; ++it) {
                decltype(auto) maybeChildren = this->protocol().childRows(*it);
                if (QRangeModelDetails::isValid(maybeChildren)) {
                    auto &childrenRef = QRangeModelDetails::refTo(maybeChildren);
                    auto *parentRow = QRangeModelDetails::pointerTo(*it);
 
                    int row = 0;
                    for (auto &child : childrenRef) {
                        const_row_ptr oldParent = this->protocol().parentRow(child);
                        if (oldParent != parentRow) {
                            if (changePersistentIndexes) {
                                for (int column = pmiFromColumn; column <= pmiToColumn; ++column) {
                                    this->changePersistentIndex(this->createIndex(row, column, oldParent),
                                                                this->createIndex(row, column, parentRow));
                                }
                            }
                            this->protocol().setParentRow(child, parentRow);
                        }
                        ++row;
                    }
                    resetParentInChildrenRecursive(&childrenRef, pmiFromColumn, pmiToColumn);
                }
            }
        }
    }
 
    bool autoConnectPropertiesRange(const range_type &range, const QModelIndex &parent) const
    {
        int rowIndex = 0;
        for (const auto &row : range) {
            if (!this->autoConnectPropertiesInRow(row, rowIndex, parent))
                return false;
            Q_ASSERT(QRangeModelDetails::isValid(row));
            const auto &children = this->protocol().childRows(QRangeModelDetails::refTo(row));
            if (QRangeModelDetails::isValid(children)) {
                if (!autoConnectPropertiesRange(QRangeModelDetails::refTo(children),
                                                this->itemModel().index(rowIndex, 0, parent))) {
                    return false;
                }
            }
            ++rowIndex;
        }
        return true;
    }
 
    bool autoConnectPropertiesImpl() const
    {
        return autoConnectPropertiesRange(*this->m_data.model(), {});
    }
 
    decltype(auto) rowDataImpl(const QModelIndex &index) const
    {
        const_row_ptr parentRow = static_cast<const_row_ptr>(index.constInternalPointer());
        const range_type &siblings = childrenOf(parentRow);
        Q_ASSERT(index.row() < int(Base::size(siblings)));
        return *QRangeModelDetails::pos(siblings, index.row());
    }
 
    decltype(auto) rowDataImpl(const QModelIndex &index)
    {
        row_ptr parentRow = static_cast<row_ptr>(index.internalPointer());
        range_type &siblings = childrenOf(parentRow);
        Q_ASSERT(index.row() < int(Base::size(siblings)));
        return *QRangeModelDetails::pos(siblings, index.row());
    }
 
    const range_type *childRangeImpl(const QModelIndex &index) const
    {
        const auto &row = this->rowData(index);
        if (!QRangeModelDetails::isValid(row))
            return static_cast<const range_type *>(nullptr);
 
        decltype(auto) children = this->protocol().childRows(QRangeModelDetails::refTo(row));
        return QRangeModelDetails::pointerTo(std::forward<decltype(children)>(children));
    }
 
    range_type *childRangeImpl(const QModelIndex &index)
    {
        auto &row = this->rowData(index);
        if (!QRangeModelDetails::isValid(row))
            return static_cast<range_type *>(nullptr);
 
        decltype(auto) children = this->protocol().childRows(QRangeModelDetails::refTo(row));
        using Children = std::remove_reference_t<decltype(children)>;
 
        if constexpr (QRangeModelDetails::is_any_of<Children, std::optional>())
            if constexpr (std::is_default_constructible<typename Children::value_type>()) {
                if (!children)
                    children.emplace(range_type{});
            }
 
        return QRangeModelDetails::pointerTo(std::forward<decltype(children)>(children));
    }
 
    const range_type &childrenOf(const_row_ptr row) const
    {
        return row ? QRangeModelDetails::refTo(this->protocol().childRows(*row))
                   : *this->m_data.model();
    }
 
    range_type &childrenOf(row_ptr row)
    {
        return row ? QRangeModelDetails::refTo(this->protocol().childRows(*row))
                   : *this->m_data.model();
    }
 
    template <typename LessThan>
    void sortImplRecursive(range_type &range, row_ptr parentRow, const LessThan &lessThan)
    {
        for (auto &row : range) {
            decltype(auto) children = this->protocol().childRows(QRangeModelDetails::refTo(row));
            if (QRangeModelDetails::isValid(children)) {
                sortImplRecursive(QRangeModelDetails::refTo(children),
                                  QRangeModelDetails::pointerTo(row), lessThan);
            }
        }
        this->sortSubRange(range, parentRow, lessThan);
    }
 
    template <typename LessThan>
    void sortImpl(const LessThan &lessThan)
    {
        sortImplRecursive(*this->m_data.model(), nullptr, lessThan);
        resetParentInChildren(this->m_data.model());
    }
 
    void prunePersistentIndexList(QModelIndexList &list, row_ptr expectedParent)
    {
        erase_if(list, [expectedParent](const QModelIndex &index){
            return static_cast<row_ptr>(index.internalPointer()) != expectedParent;
        });
    }
 
    void matchImplRecursive(const range_type &range, const_row_ptr parentPtr, int from, int to,
                            int role, const QVariant &value, int hits, Qt::MatchFlags flags, int column,
                            QModelIndexList &result, const QCollator &collator) const
    {
        auto it = QRangeModelDetails::pos(range, from);
        auto end = QRangeModelDetails::adl_end(range);
 
        const bool recurse = flags.testAnyFlag(Qt::MatchRecursive);
        const bool allHits = (hits == -1);
 
        for (int r = from; it != end && r < to && (allHits || result.size() < hits); ++it, ++r) {
            const QModelIndex index = this->createIndex(r, column, parentPtr);
            if (this->matchRow(*it, index, role, value, flags, collator))
                result.append(index);
 
            if (recurse) {
                decltype(auto) children = this->protocol().childRows(QRangeModelDetails::refTo(*it));
 
                if (QRangeModelDetails::isValid(children)) {
                    matchImplRecursive(QRangeModelDetails::refTo(children),
                                       QRangeModelDetails::pointerTo(*it), 0,
                                       int(QRangeModelDetails::size(QRangeModelDetails::refTo(children))),
                                       role, value, hits, flags, column, result, collator);
                }
            }
        }
    }
 
    QModelIndexList matchImpl(const QModelIndex &start, int role, const QVariant &value, int hits,
                   Qt::MatchFlags flags, const QCollator &collator) const
    {
        QModelIndexList result;
        const bool wrap = flags.testAnyFlag(Qt::MatchWrap);
        const int column = start.column();
        const int from = start.row();
        const int to = this->rowCount(start.parent());
 
        for (int i = 0; (wrap && i < 2) || (!wrap && i < 1); ++i) {
            const int fromRow = (i == 0) ? from : 0;
            const int toRow = (i == 0) ? to : from;
            matchImplRecursive(*this->m_data.model(), nullptr, fromRow, toRow,
                               role, value, hits, flags, column, result, collator);
        }
        return result;
    }
 
    // tree models don't overwrite the data at index, but instead insert a
    // child item
    bool dropOnItem(const QMimeData *, const QModelIndex &)
    {
        return false;
    }
};
 
// specialization for flat models without protocol
template <typename Range>
class QGenericTableItemModelImpl
    : public QRangeModelImpl<QGenericTableItemModelImpl<Range>, Range>
{
    using Base = QRangeModelImpl<QGenericTableItemModelImpl<Range>, Range>;
    friend class QRangeModelImpl<QGenericTableItemModelImpl<Range>, Range>;
 
    static constexpr bool is_mutable_impl = true;
 
public:
    using range_type = typename Base::range_type;
    using range_features = typename Base::range_features;
    using row_type = typename Base::row_type;
    using row_ptr = typename Base::row_ptr;
    using const_row_ptr = typename Base::const_row_ptr;
    using row_traits = typename Base::row_traits;
    using row_features = typename Base::row_features;
 
    explicit QGenericTableItemModelImpl(Range &&model, QRangeModel *itemModel)
        : Base(std::forward<Range>(model), {}, itemModel)
    {}
 
protected:
    QModelIndex indexImpl(int row, int column, const QModelIndex &) const
    {
        if constexpr (Base::dynamicColumns()) {
            if (column < int(Base::size(*QRangeModelDetails::pos(*this->m_data.model(), row))))
                return this->createIndex(row, column);
#ifndef QT_NO_DEBUG
            // if we got here, then column < columnCount(), but this row is too short
            qCritical("QRangeModel: Column-range at row %d is not large enough!", row);
#endif
            return {};
        } else {
            return this->createIndex(row, column);
        }
    }
 
    QModelIndex parentImpl(const QModelIndex &) const
    {
        return {};
    }
 
    int rowCountImpl(const QModelIndex &parent) const
    {
        if (parent.isValid())
            return 0;
        return int(Base::size(*this->m_data.model()));
    }
 
    int columnCountImpl(const QModelIndex &parent) const
    {
        if (parent.isValid())
            return 0;
 
        // in a table, all rows have the same number of columns (as the first row)
        if constexpr (Base::dynamicColumns()) {
            return int(Base::size(*this->m_data.model()) == 0
                       ? 0
                       : Base::size(*QRangeModelDetails::adl_begin(*this->m_data.model())));
        } else {
            return Base::fixedColumnCount();
        }
    }
 
    static constexpr Qt::ItemFlags defaultFlags()
    {
        return Qt::ItemIsEnabled | Qt::ItemIsSelectable | Qt::ItemNeverHasChildren;
    }
 
    static constexpr bool canInsertRowsImpl()
    {
        return Base::dynamicRows() && range_features::has_insert;
    }
 
    static constexpr bool canRemoveRowsImpl()
    {
        return Base::dynamicRows() && range_features::has_erase;
    }
 
    static constexpr bool canMoveColumns(const QModelIndex &source, const QModelIndex &destination)
    {
        return !source.isValid() && !destination.isValid();
    }
 
    static constexpr bool canMoveRows(const QModelIndex &source, const QModelIndex &destination)
    {
        return !source.isValid() && !destination.isValid();
    }
 
    constexpr bool moveRowsAcross(const QModelIndex &, int , int,
                                  const QModelIndex &, int) noexcept
    {
        // table/flat model: can't move rows between different parents
        return false;
    }
 
    auto makeEmptyRow(typename Base::row_ptr)
    {
        row_type empty_row = this->protocol().newRow();
 
        // dynamically sized rows all have to have the same column count
        if constexpr (Base::dynamicColumns() && row_features::has_resize) {
            if (QRangeModelDetails::isValid(empty_row))
                QRangeModelDetails::refTo(empty_row).resize(this->columnCount({}));
        }
 
        return empty_row;
    }
 
    template <typename It, typename Sentinel>
    void deleteRemovedRows(It &&begin, Sentinel &&end)
    {
        if constexpr (Base::protocol_traits::has_deleteRow) {
            for (auto it = begin; it != end; ++it)
                this->protocol().deleteRow(std::move(*it));
        }
    }
 
    decltype(auto) rowDataImpl(const QModelIndex &index) const
    {
        Q_ASSERT(q20::cmp_less(index.row(), Base::size(*this->m_data.model())));
        return *QRangeModelDetails::pos(*this->m_data.model(), index.row());
    }
 
    decltype(auto) rowDataImpl(const QModelIndex &index)
    {
        Q_ASSERT(q20::cmp_less(index.row(), Base::size(*this->m_data.model())));
        return *QRangeModelDetails::pos(*this->m_data.model(), index.row());
    }
 
    const range_type *childRangeImpl(const QModelIndex &) const
    {
        return nullptr;
    }
 
    range_type *childRangeImpl(const QModelIndex &)
    {
        return nullptr;
    }
 
    const range_type &childrenOf(const_row_ptr row) const
    {
        Q_ASSERT(!row);
        return *this->m_data.model();
    }
 
    range_type &childrenOf(row_ptr row)
    {
        Q_ASSERT(!row);
        return *this->m_data.model();
    }
 
    void resetParentInChildren(range_type *)
    {
    }
 
    bool autoConnectPropertiesImpl() const
    {
        bool result = true;
        int rowIndex = 0;
        for (const auto &row : *this->m_data.model()) {
            result &= this->autoConnectPropertiesInRow(row, rowIndex, {});
            ++rowIndex;
        }
        return result;
    }
 
    template <typename LessThan>
    void sortImpl(const LessThan &lessThan)
    {
        this->sortSubRange(*this->m_data.model(), nullptr, lessThan);
    }
 
    void prunePersistentIndexList(QModelIndexList &, typename Base::row_ptr) {}
 
    QModelIndexList matchImpl(const QModelIndex &start, int role, const QVariant &value,
                              int hits, Qt::MatchFlags flags, const QCollator &collator) const
    {
        QModelIndexList result;
        const bool wrap = flags.testAnyFlag(Qt::MatchWrap);
        const bool allHits = (hits == -1);
        const int column = start.column();
        int from = start.row();
        int to = this->rowCount({});
        decltype(auto) siblings = *this->m_data.model();
 
        for (int i = 0; (wrap && i < 2) || (!wrap && i < 1); ++i) {
            auto it = QRangeModelDetails::pos(siblings, from);
            auto end = QRangeModelDetails::adl_end(siblings);
            for (int r = from; it != end && r < to && (allHits || result.size() < hits);
                 ++it, ++r) {
                if (!QRangeModelDetails::isValid(*it))
                    continue;
                const QModelIndex index = this->createIndex(r, column, nullptr);
                if (this->matchRow(*it, index, role, value, flags, collator))
                    result.append(index);
            }
            from = 0;
            to = start.row();
        }
 
        return result;
    }
 
    // flat models can overwrite data of the dropped-on item
    bool dropOnItem(const QMimeData *data, const QModelIndex &index)
    {
        return this->dropDataOnItem(data, index);
    }
};
 
QT_END_NAMESPACE
 
#endif // Q_QDOC
 
#endif // QRANGEMODEL_IMPL_H