File indexing completed on 2024-05-05 03:56:41

 /*
     SPDX-FileCopyrightText: 2009 Stephen Kelly <steveire@gmail.com>
     SPDX-FileCopyrightText: 2010 Klarälvdalens Datakonsult AB, a KDAB Group company <info@kdab.net>
     SPDX-FileContributor: Stephen Kelly <stephen@kdab.com>
 
     SPDX-License-Identifier: LGPL-2.0-or-later
 */
 
 #include "kdescendantsproxymodel.h"
 
 #include <QStringList>
 
 #include "kbihash_p.h"
 
 typedef KHash2Map<QPersistentModelIndex, int> Mapping;
 
 class KDescendantsProxyModelPrivate
 {
     KDescendantsProxyModelPrivate(KDescendantsProxyModel *qq)
         : q_ptr(qq)
         , m_rowCount(0)
         , m_ignoreNextLayoutAboutToBeChanged(false)
         , m_ignoreNextLayoutChanged(false)
         , m_relayouting(false)
         , m_displayAncestorData(false)
         , m_ancestorSeparator(QStringLiteral(" / "))
     {
     }
 
     Q_DECLARE_PUBLIC(KDescendantsProxyModel)
     KDescendantsProxyModel *const q_ptr;
 
     mutable QList<QPersistentModelIndex> m_pendingParents;
 
     void scheduleProcessPendingParents() const;
     void processPendingParents();
 
     void synchronousMappingRefresh();
 
     void updateInternalIndexes(int start, int offset);
 
     void resetInternalData();
 
     void notifyhasSiblings(const QModelIndex &parent);
     void sourceRowsAboutToBeInserted(const QModelIndex &, int, int);
     void sourceRowsInserted(const QModelIndex &, int, int);
     void sourceRowsAboutToBeRemoved(const QModelIndex &, int, int);
     void sourceRowsRemoved(const QModelIndex &, int, int);
     void sourceRowsAboutToBeMoved(const QModelIndex &, int, int, const QModelIndex &, int);
     void sourceRowsMoved(const QModelIndex &, int, int, const QModelIndex &, int);
     void sourceModelAboutToBeReset();
     void sourceModelReset();
     void sourceLayoutAboutToBeChanged();
     void sourceLayoutChanged();
     void sourceDataChanged(const QModelIndex &, const QModelIndex &);
     void sourceModelDestroyed();
 
     Mapping m_mapping;
     int m_rowCount;
     QPair<int, int> m_removePair;
     QPair<int, int> m_insertPair;
 
     bool m_expandsByDefault = true;
     bool m_ignoreNextLayoutAboutToBeChanged;
     bool m_ignoreNextLayoutChanged;
     bool m_relayouting;
 
     bool m_displayAncestorData;
     QString m_ancestorSeparator;
 
     QSet<QPersistentModelIndex> m_expandedSourceIndexes;
     QSet<QPersistentModelIndex> m_collapsedSourceIndexes;
 
     QList<QPersistentModelIndex> m_layoutChangePersistentIndexes;
     QModelIndexList m_proxyIndexes;
 };
 
 void KDescendantsProxyModelPrivate::resetInternalData()
 {
     m_rowCount = 0;
     m_mapping.clear();
     m_layoutChangePersistentIndexes.clear();
     m_proxyIndexes.clear();
 }
 
 void KDescendantsProxyModelPrivate::synchronousMappingRefresh()
 {
     m_rowCount = 0;
     m_mapping.clear();
     m_pendingParents.clear();
 
     m_pendingParents.append(QModelIndex());
 
     m_relayouting = true;
     while (!m_pendingParents.isEmpty()) {
         processPendingParents();
     }
     m_relayouting = false;
 }
 
 void KDescendantsProxyModelPrivate::scheduleProcessPendingParents() const
 {
     const_cast<KDescendantsProxyModelPrivate *>(this)->processPendingParents();
 }
 
 void KDescendantsProxyModelPrivate::processPendingParents()
 {
     Q_Q(KDescendantsProxyModel);
     const QList<QPersistentModelIndex>::iterator begin = m_pendingParents.begin();
     QList<QPersistentModelIndex>::iterator it = begin;
 
     const QList<QPersistentModelIndex>::iterator end = m_pendingParents.end();
 
     QList<QPersistentModelIndex> newPendingParents;
 
     while (it != end && it != m_pendingParents.end()) {
         const QModelIndex sourceParent = *it;
         if (!sourceParent.isValid() && m_rowCount > 0) {
             // It was removed from the source model before it was inserted.
             it = m_pendingParents.erase(it);
             continue;
         }
         if (!q->isSourceIndexVisible(sourceParent)) {
             // It's a collapsed node, or its parents are collapsed, ignore.
             it = m_pendingParents.erase(it);
             continue;
         }
 
         const int rowCount = q->sourceModel()->rowCount(sourceParent);
 
         // A node can be marked as collapsed or expanded even if it doesn't have children
         if (rowCount == 0) {
             it = m_pendingParents.erase(it);
             continue;
         }
         const QPersistentModelIndex sourceIndex = q->sourceModel()->index(rowCount - 1, 0, sourceParent);
 
         Q_ASSERT(sourceIndex.isValid());
 
         const QModelIndex proxyParent = q->mapFromSource(sourceParent);
 
         Q_ASSERT(sourceParent.isValid() == proxyParent.isValid());
         const int proxyEndRow = proxyParent.row() + rowCount;
         const int proxyStartRow = proxyEndRow - rowCount + 1;
 
         if (!m_relayouting) {
             q->beginInsertRows(QModelIndex(), proxyStartRow, proxyEndRow);
         }
 
         updateInternalIndexes(proxyStartRow, rowCount);
         m_mapping.insert(sourceIndex, proxyEndRow);
         it = m_pendingParents.erase(it);
         m_rowCount += rowCount;
 
         if (!m_relayouting) {
             q->endInsertRows();
         }
 
         for (int sourceRow = 0; sourceRow < rowCount; ++sourceRow) {
             static const int column = 0;
             const QModelIndex child = q->sourceModel()->index(sourceRow, column, sourceParent);
             Q_ASSERT(child.isValid());
 
             if (q->sourceModel()->hasChildren(child) && q->isSourceIndexExpanded(child) && q->sourceModel()->rowCount(child) > 0) {
                 newPendingParents.append(child);
             }
         }
     }
     m_pendingParents += newPendingParents;
     if (!m_pendingParents.isEmpty()) {
         processPendingParents();
     }
     //   scheduleProcessPendingParents();
 }
 
 void KDescendantsProxyModelPrivate::updateInternalIndexes(int start, int offset)
 {
     // TODO: Make KHash2Map support key updates and do this backwards.
     QHash<int, QPersistentModelIndex> updates;
     {
         Mapping::right_iterator it = m_mapping.rightLowerBound(start);
         const Mapping::right_iterator end = m_mapping.rightEnd();
 
         while (it != end) {
             updates.insert(it.key() + offset, *it);
             ++it;
         }
     }
 
     {
         QHash<int, QPersistentModelIndex>::const_iterator it = updates.constBegin();
         const QHash<int, QPersistentModelIndex>::const_iterator end = updates.constEnd();
 
         for (; it != end; ++it) {
             m_mapping.insert(it.value(), it.key());
         }
     }
 }
 
 KDescendantsProxyModel::KDescendantsProxyModel(QObject *parent)
     : QAbstractProxyModel(parent)
     , d_ptr(new KDescendantsProxyModelPrivate(this))
 {
 }
 
 KDescendantsProxyModel::~KDescendantsProxyModel() = default;
 
 QHash<int, QByteArray> KDescendantsProxyModel::roleNames() const
 {
     QHash<int, QByteArray> roleNames = QAbstractProxyModel::roleNames();
 
     roleNames[LevelRole] = "kDescendantLevel";
     roleNames[ExpandableRole] = "kDescendantExpandable";
     roleNames[ExpandedRole] = "kDescendantExpanded";
     roleNames[HasSiblingsRole] = "kDescendantHasSiblings";
     return roleNames;
 }
 
 void KDescendantsProxyModel::setExpandsByDefault(bool expand)
 {
     if (d_ptr->m_expandsByDefault == expand) {
         return;
     }
 
     beginResetModel();
     d_ptr->m_expandsByDefault = expand;
     d_ptr->m_expandedSourceIndexes.clear();
     d_ptr->m_collapsedSourceIndexes.clear();
     endResetModel();
 }
 
 bool KDescendantsProxyModel::expandsByDefault() const
 {
     return d_ptr->m_expandsByDefault;
 }
 
 bool KDescendantsProxyModel::isSourceIndexExpanded(const QModelIndex &sourceIndex) const
 {
     // Root is always expanded
     if (!sourceIndex.isValid()) {
         return true;
     } else if (d_ptr->m_expandsByDefault) {
         return !d_ptr->m_collapsedSourceIndexes.contains(QPersistentModelIndex(sourceIndex));
     } else {
         return d_ptr->m_expandedSourceIndexes.contains(QPersistentModelIndex(sourceIndex));
     }
 }
 
 bool KDescendantsProxyModel::isSourceIndexVisible(const QModelIndex &sourceIndex) const
 {
     // Root is always visible
     if (!sourceIndex.isValid()) {
         return true;
     }
 
     QModelIndex index(sourceIndex);
     do {
         index = index.parent();
         if (!index.isValid()) {
             return true;
         }
     } while (isSourceIndexExpanded(index));
 
     return false;
 }
 
 void KDescendantsProxyModel::expandSourceIndex(const QModelIndex &sourceIndex)
 {
     if (!sourceIndex.isValid() || isSourceIndexExpanded(sourceIndex)) {
         return;
     }
 
     if (d_ptr->m_expandsByDefault) {
         d_ptr->m_collapsedSourceIndexes.remove(QPersistentModelIndex(sourceIndex));
     } else {
         d_ptr->m_expandedSourceIndexes << QPersistentModelIndex(sourceIndex);
     }
 
     d_ptr->m_pendingParents << sourceIndex;
     d_ptr->scheduleProcessPendingParents();
     Q_EMIT sourceIndexExpanded(sourceIndex);
 
     const QModelIndex index = mapFromSource(sourceIndex);
     Q_EMIT dataChanged(index, index, {ExpandedRole});
 }
 
 void KDescendantsProxyModel::collapseSourceIndex(const QModelIndex &sourceIndex)
 {
     if (!sourceIndex.isValid() || !isSourceIndexExpanded(sourceIndex)) {
         return;
     }
 
     const int row = mapFromSource(sourceIndex).row();
     const int rowStart = row + 1;
     int rowEnd = row;
 
     QList<QModelIndex> toVisit = {sourceIndex};
     QSet<QModelIndex> visited;
     while (!toVisit.isEmpty()) {
         QModelIndex index = toVisit.takeLast();
         if (!visited.contains(index)) {
             visited << index;
             const int nRows = sourceModel()->rowCount(index);
             rowEnd += nRows;
             for (int i = 0; i < nRows; ++i) {
                 QModelIndex child = sourceModel()->index(i, 0, index);
                 if (isSourceIndexExpanded(child)) {
                     toVisit << child;
                 }
             }
         }
     }
 
     beginRemoveRows(QModelIndex(), rowStart, rowEnd);
 
     if (d_ptr->m_expandsByDefault) {
         d_ptr->m_collapsedSourceIndexes << QPersistentModelIndex(sourceIndex);
     } else {
         d_ptr->m_expandedSourceIndexes.remove(QPersistentModelIndex(sourceIndex));
     }
 
     {
         Mapping::right_iterator it = d_ptr->m_mapping.rightLowerBound(rowStart);
         const Mapping::right_iterator endIt = d_ptr->m_mapping.rightUpperBound(rowEnd);
 
         if (endIt != d_ptr->m_mapping.rightEnd()) {
             while (it != endIt) {
                 it = d_ptr->m_mapping.eraseRight(it);
             }
         } else {
             while (it != d_ptr->m_mapping.rightUpperBound(rowEnd)) {
                 it = d_ptr->m_mapping.eraseRight(it);
             }
         }
     }
 
     d_ptr->m_removePair = qMakePair(rowStart, rowEnd);
 
     d_ptr->synchronousMappingRefresh();
     endRemoveRows();
     Q_EMIT sourceIndexCollapsed(sourceIndex);
 
     const QModelIndex ownIndex = mapFromSource(sourceIndex);
     Q_EMIT dataChanged(ownIndex, ownIndex, {ExpandedRole});
 }
 
 QModelIndexList KDescendantsProxyModel::match(const QModelIndex &start, int role, const QVariant &value, int hits, Qt::MatchFlags flags) const
 {
     return QAbstractProxyModel::match(start, role, value, hits, flags);
 }
 
 namespace
 {
 // we only work on DisplayRole for now
 static const QList<int> changedRoles = {Qt::DisplayRole};
 }
 
 void KDescendantsProxyModel::setDisplayAncestorData(bool display)
 {
     Q_D(KDescendantsProxyModel);
     bool displayChanged = (display != d->m_displayAncestorData);
     d->m_displayAncestorData = display;
     if (displayChanged) {
         Q_EMIT displayAncestorDataChanged();
         // send out big hammer. Everything needs to be updated.
         Q_EMIT dataChanged(index(0, 0), index(rowCount() - 1, columnCount() - 1), changedRoles);
     }
 }
 
 bool KDescendantsProxyModel::displayAncestorData() const
 {
     Q_D(const KDescendantsProxyModel);
     return d->m_displayAncestorData;
 }
 
 void KDescendantsProxyModel::setAncestorSeparator(const QString &separator)
 {
     Q_D(KDescendantsProxyModel);
     bool separatorChanged = (separator != d->m_ancestorSeparator);
     d->m_ancestorSeparator = separator;
     if (separatorChanged) {
         Q_EMIT ancestorSeparatorChanged();
         if (d->m_displayAncestorData) {
             // send out big hammer. Everything needs to be updated.
             Q_EMIT dataChanged(index(0, 0), index(rowCount() - 1, columnCount() - 1), changedRoles);
         }
     }
 }
 
 QString KDescendantsProxyModel::ancestorSeparator() const
 {
     Q_D(const KDescendantsProxyModel);
     return d->m_ancestorSeparator;
 }
 
 void KDescendantsProxyModel::setSourceModel(QAbstractItemModel *_sourceModel)
 {
     Q_D(KDescendantsProxyModel);
 
     beginResetModel();
 
     if (sourceModel()) {
         disconnect(sourceModel(), nullptr, this, nullptr);
     }
 
     QAbstractProxyModel::setSourceModel(_sourceModel);
     d_ptr->m_expandedSourceIndexes.clear();
 
     if (_sourceModel) {
         connect(_sourceModel, &QAbstractItemModel::rowsAboutToBeInserted, this, [d](const QModelIndex &parent, int start, int end) {
             d->sourceRowsAboutToBeInserted(parent, start, end);
         });
 
         connect(_sourceModel, &QAbstractItemModel::rowsInserted, this, [d](const QModelIndex &parent, int start, int end) {
             d->sourceRowsInserted(parent, start, end);
         });
 
         connect(_sourceModel, &QAbstractItemModel::rowsAboutToBeRemoved, this, [d](const QModelIndex &parent, int start, int end) {
             d->sourceRowsAboutToBeRemoved(parent, start, end);
         });
 
         connect(_sourceModel, &QAbstractItemModel::rowsRemoved, this, [d](const QModelIndex &parent, int start, int end) {
             d->sourceRowsRemoved(parent, start, end);
         });
 
         connect(_sourceModel,
                 &QAbstractItemModel::rowsAboutToBeMoved,
                 this,
                 [d](const QModelIndex &srcParent, int srcStart, int srcEnd, const QModelIndex &destParent, int destStart) {
                     d->sourceRowsAboutToBeMoved(srcParent, srcStart, srcEnd, destParent, destStart);
                 });
 
         connect(_sourceModel,
                 &QAbstractItemModel::rowsMoved,
                 this,
                 [d](const QModelIndex &srcParent, int srcStart, int srcEnd, const QModelIndex &destParent, int destStart) {
                     d->sourceRowsMoved(srcParent, srcStart, srcEnd, destParent, destStart);
                 });
 
         connect(_sourceModel, &QAbstractItemModel::modelAboutToBeReset, this, [d]() {
             d->sourceModelAboutToBeReset();
         });
 
         connect(_sourceModel, &QAbstractItemModel::modelReset, this, [d]() {
             d->sourceModelReset();
         });
 
         connect(_sourceModel, &QAbstractItemModel::dataChanged, this, [d](const QModelIndex &topLeft, const QModelIndex &bottomRight) {
             d->sourceDataChanged(topLeft, bottomRight);
         });
 
         connect(_sourceModel, &QAbstractItemModel::layoutAboutToBeChanged, this, [d]() {
             d->sourceLayoutAboutToBeChanged();
         });
 
         connect(_sourceModel, &QAbstractItemModel::layoutChanged, this, [d]() {
             d->sourceLayoutChanged();
         });
 
         connect(_sourceModel, &QObject::destroyed, this, [d]() {
             d->sourceModelDestroyed();
         });
     }
 
     resetInternalData();
     if (_sourceModel && _sourceModel->hasChildren()) {
         d->synchronousMappingRefresh();
     }
 
     endResetModel();
     Q_EMIT sourceModelChanged();
 }
 
 QModelIndex KDescendantsProxyModel::parent(const QModelIndex &index) const
 {
     Q_UNUSED(index)
     return QModelIndex();
 }
 
 bool KDescendantsProxyModel::hasChildren(const QModelIndex &parent) const
 {
     Q_D(const KDescendantsProxyModel);
     return !(d->m_mapping.isEmpty() || parent.isValid());
 }
 
 int KDescendantsProxyModel::rowCount(const QModelIndex &parent) const
 {
     Q_D(const KDescendantsProxyModel);
     if (d->m_pendingParents.contains(parent) || parent.isValid() || !sourceModel()) {
         return 0;
     }
 
     if (d->m_mapping.isEmpty() && sourceModel()->hasChildren()) {
         const_cast<KDescendantsProxyModelPrivate *>(d)->synchronousMappingRefresh();
     }
     return d->m_rowCount;
 }
 
 QModelIndex KDescendantsProxyModel::index(int row, int column, const QModelIndex &parent) const
 {
     if (parent.isValid()) {
         return QModelIndex();
     }
 
     if (!hasIndex(row, column, parent)) {
         return QModelIndex();
     }
 
     return createIndex(row, column);
 }
 
 QModelIndex KDescendantsProxyModel::mapToSource(const QModelIndex &proxyIndex) const
 {
     Q_D(const KDescendantsProxyModel);
     if (d->m_mapping.isEmpty() || !proxyIndex.isValid() || !sourceModel()) {
         return QModelIndex();
     }
 
     const Mapping::right_const_iterator result = d->m_mapping.rightLowerBound(proxyIndex.row());
     Q_ASSERT(result != d->m_mapping.rightEnd());
 
     const int proxyLastRow = result.key();
     const QModelIndex sourceLastChild = result.value();
     Q_ASSERT(sourceLastChild.isValid());
 
     // proxyLastRow is greater than proxyIndex.row().
     // sourceLastChild is vertically below the result we're looking for
     // and not necessarily in the correct parent.
     // We travel up through its parent hierarchy until we are in the
     // right parent, then return the correct sibling.
 
     // Source:           Proxy:    Row
     // - A               - A       - 0
     // - B               - B       - 1
     // - C               - C       - 2
     // - D               - D       - 3
     // - - E             - E       - 4
     // - - F             - F       - 5
     // - - G             - G       - 6
     // - - H             - H       - 7
     // - - I             - I       - 8
     // - - - J           - J       - 9
     // - - - K           - K       - 10
     // - - - L           - L       - 11
     // - - M             - M       - 12
     // - - N             - N       - 13
     // - O               - O       - 14
 
     // Note that L, N and O are lastChildIndexes, and therefore have a mapping. If we
     // are trying to map G from the proxy to the source, We at this point have an iterator
     // pointing to (L -> 11). The proxy row of G is 6. (proxyIndex.row() == 6). We seek the
     // sourceIndex which is vertically above L by the distance proxyLastRow - proxyIndex.row().
     // In this case the verticalDistance is 5.
 
     int verticalDistance = proxyLastRow - proxyIndex.row();
 
     // We traverse the ancestors of L, until we can index the desired row in the source.
 
     QModelIndex ancestor = sourceLastChild;
     while (ancestor.isValid()) {
         const int ancestorRow = ancestor.row();
         if (verticalDistance <= ancestorRow) {
             return ancestor.sibling(ancestorRow - verticalDistance, proxyIndex.column());
         }
         verticalDistance -= (ancestorRow + 1);
         ancestor = ancestor.parent();
     }
     Q_ASSERT(!"Didn't find target row.");
     return QModelIndex();
 }
 
 QModelIndex KDescendantsProxyModel::mapFromSource(const QModelIndex &sourceIndex) const
 {
     Q_D(const KDescendantsProxyModel);
 
     if (!sourceModel()) {
         return QModelIndex();
     }
 
     if (d->m_mapping.isEmpty()) {
         return QModelIndex();
     }
 
     {
         // TODO: Consider a parent Mapping to speed this up.
 
         Mapping::right_const_iterator it = d->m_mapping.rightConstBegin();
         const Mapping::right_const_iterator end = d->m_mapping.rightConstEnd();
         const QModelIndex sourceParent = sourceIndex.parent();
         Mapping::right_const_iterator result = end;
 
         if (!isSourceIndexVisible(sourceIndex)) {
             return QModelIndex();
         }
 
         for (; it != end; ++it) {
             QModelIndex index = it.value();
             bool found_block = false;
             while (index.isValid()) {
                 const QModelIndex ancestor = index.parent();
                 if (ancestor == sourceParent && index.row() >= sourceIndex.row()) {
                     found_block = true;
                     if (result == end || it.key() < result.key()) {
                         result = it;
                         break; // Leave the while loop. index is still valid.
                     }
                 }
                 index = ancestor;
             }
             if (found_block && !index.isValid())
             // Looked through the ascendants of it.key() without finding sourceParent.
             // That means we've already got the result we need.
             {
                 break;
             }
         }
         Q_ASSERT(result != end);
         const QModelIndex sourceLastChild = result.value();
         int proxyRow = result.key();
         QModelIndex index = sourceLastChild;
         while (index.isValid()) {
             const QModelIndex ancestor = index.parent();
             if (ancestor == sourceParent) {
                 return createIndex(proxyRow - (index.row() - sourceIndex.row()), sourceIndex.column());
             }
             proxyRow -= (index.row() + 1);
             index = ancestor;
         }
         Q_ASSERT(!"Didn't find valid proxy mapping.");
         return QModelIndex();
     }
 }
 
 int KDescendantsProxyModel::columnCount(const QModelIndex &parent) const
 {
     if (parent.isValid() /* || rowCount(parent) == 0 */ || !sourceModel()) {
         return 0;
     }
 
     return sourceModel()->columnCount();
 }
 
 QVariant KDescendantsProxyModel::data(const QModelIndex &index, int role) const
 {
     Q_D(const KDescendantsProxyModel);
 
     if (!sourceModel()) {
         return QVariant();
     }
 
     if (!index.isValid()) {
         return sourceModel()->data(index, role);
     }
 
     QModelIndex sourceIndex = mapToSource(index);
 
     if ((d->m_displayAncestorData) && (role == Qt::DisplayRole)) {
         if (!sourceIndex.isValid()) {
             return QVariant();
         }
         QString displayData = sourceIndex.data().toString();
         sourceIndex = sourceIndex.parent();
         while (sourceIndex.isValid()) {
             displayData.prepend(d->m_ancestorSeparator);
             displayData.prepend(sourceIndex.data().toString());
             sourceIndex = sourceIndex.parent();
         }
         return displayData;
     } else if (role == LevelRole) {
         QModelIndex sourceIndex = mapToSource(index);
         int level = 0;
         while (sourceIndex.isValid()) {
             sourceIndex = sourceIndex.parent();
             ++level;
         }
         return level;
     } else if (role == ExpandableRole) {
         QModelIndex sourceIndex = mapToSource(index);
         return sourceModel()->hasChildren(sourceIndex);
     } else if (role == ExpandedRole) {
         return isSourceIndexExpanded(mapToSource(index));
     } else if (role == HasSiblingsRole) {
         QModelIndex sourceIndex = mapToSource(index);
         QList<bool> hasSibling;
         while (sourceIndex.isValid()) {
             hasSibling.prepend(sourceModel()->rowCount(sourceIndex.parent()) > sourceIndex.row() + 1);
             sourceIndex = sourceIndex.parent();
         }
         return QVariant::fromValue(hasSibling);
     } else {
         return sourceIndex.data(role);
     }
 }
 
 QVariant KDescendantsProxyModel::headerData(int section, Qt::Orientation orientation, int role) const
 {
     if (!sourceModel() || columnCount() <= section) {
         return QVariant();
     }
 
     // Here is safe to do sourceModel()->headerData, as in this proxy we neither filter out nor reorder columns
     return sourceModel()->headerData(section, orientation, role);
 }
 
 Qt::ItemFlags KDescendantsProxyModel::flags(const QModelIndex &index) const
 {
     if (!index.isValid() || !sourceModel()) {
         return QAbstractProxyModel::flags(index);
     }
 
     const QModelIndex srcIndex = mapToSource(index);
     Q_ASSERT(srcIndex.isValid());
     return sourceModel()->flags(srcIndex);
 }
 
 void KDescendantsProxyModelPrivate::notifyhasSiblings(const QModelIndex &parent)
 {
     Q_Q(KDescendantsProxyModel);
 
     if (!parent.isValid()) {
         return;
     }
 
     QModelIndex localParent = q->mapFromSource(parent);
     Q_EMIT q->dataChanged(localParent, localParent, {KDescendantsProxyModel::HasSiblingsRole});
     for (int i = 0; i < q->sourceModel()->rowCount(parent); ++i) {
         notifyhasSiblings(q->sourceModel()->index(i, 0, parent));
     }
 }
 
 void KDescendantsProxyModelPrivate::sourceRowsAboutToBeInserted(const QModelIndex &parent, int start, int end)
 {
     Q_Q(KDescendantsProxyModel);
 
     if (parent.isValid() && (!q->isSourceIndexExpanded(parent) || !q->isSourceIndexVisible(parent))) {
         return;
     }
 
     if (!q->sourceModel()->hasChildren(parent)) {
         Q_ASSERT(q->sourceModel()->rowCount(parent) == 0);
         // parent was not a parent before.
         return;
     }
 
     int proxyStart = -1;
 
     const int rowCount = q->sourceModel()->rowCount(parent);
 
     if (rowCount > start) {
         const QModelIndex belowStart = q->sourceModel()->index(start, 0, parent);
         proxyStart = q->mapFromSource(belowStart).row();
     } else if (rowCount == 0) {
         proxyStart = q->mapFromSource(parent).row() + 1;
     } else {
         Q_ASSERT(rowCount == start);
         static const int column = 0;
         QModelIndex idx = q->sourceModel()->index(rowCount - 1, column, parent);
         while (q->isSourceIndexExpanded(idx) && q->sourceModel()->hasChildren(idx) && q->sourceModel()->rowCount(idx) > 0) {
             idx = q->sourceModel()->index(q->sourceModel()->rowCount(idx) - 1, column, idx);
         }
         // The last item in the list is getting a sibling below it.
         proxyStart = q->mapFromSource(idx).row() + 1;
     }
     const int proxyEnd = proxyStart + (end - start);
 
     m_insertPair = qMakePair(proxyStart, proxyEnd);
     q->beginInsertRows(QModelIndex(), proxyStart, proxyEnd);
 }
 
 void KDescendantsProxyModelPrivate::sourceRowsInserted(const QModelIndex &parent, int start, int end)
 {
     Q_Q(KDescendantsProxyModel);
     if (parent.isValid() && (!q->isSourceIndexExpanded(parent) || !q->isSourceIndexVisible(parent))) {
         const QModelIndex index = q->mapFromSource(parent);
         Q_EMIT q->dataChanged(index,
                               index,
                               {KDescendantsProxyModel::ExpandableRole, KDescendantsProxyModel::ExpandedRole, KDescendantsProxyModel::HasSiblingsRole});
         if (start > 0) {
             notifyhasSiblings(q->sourceModel()->index(start - 1, 0, parent));
         }
         return;
     }
     Q_ASSERT(q->sourceModel()->index(start, 0, parent).isValid());
 
     const int rowCount = q->sourceModel()->rowCount(parent);
     Q_ASSERT(rowCount > 0);
 
     const int difference = end - start + 1;
 
     if (rowCount == difference) {
         const QModelIndex index = q->mapFromSource(parent);
         if (parent.isValid()) {
             Q_EMIT q->dataChanged(index,
                                   index,
                                   {KDescendantsProxyModel::ExpandableRole, KDescendantsProxyModel::ExpandedRole, KDescendantsProxyModel::HasSiblingsRole});
         }
         // @p parent was not a parent before.
         m_pendingParents.append(parent);
         scheduleProcessPendingParents();
         if (start > 0) {
             notifyhasSiblings(q->sourceModel()->index(start - 1, 0, parent));
         }
         return;
     }
 
     const int proxyStart = m_insertPair.first;
 
     Q_ASSERT(proxyStart >= 0);
 
     updateInternalIndexes(proxyStart, difference);
 
     if (rowCount - 1 == end) {
         // The previously last row (the mapped one) is no longer the last.
         // For example,
 
         // - A            - A           0
         // - - B          - B           1
         // - - C          - C           2
         // - - - D        - D           3
         // - - - E   ->   - E           4
         // - - F          - F           5
         // - - G     ->   - G           6
         // - H            - H           7
         // - I       ->   - I           8
 
         // As last children, E, F and G have mappings.
         // Consider that 'J' is appended to the children of 'C', below 'E'.
 
         // - A            - A           0
         // - - B          - B           1
         // - - C          - C           2
         // - - - D        - D           3
         // - - - E   ->   - E           4
         // - - - J        - ???         5
         // - - F          - F           6
         // - - G     ->   - G           7
         // - H            - H           8
         // - I       ->   - I           9
 
         // The updateInternalIndexes call above will have updated the F and G mappings correctly because proxyStart is 5.
         // That means that E -> 4 was not affected by the updateInternalIndexes call.
         // Now the mapping for E -> 4 needs to be updated so that it's a mapping for J -> 5.
 
         Q_ASSERT(!m_mapping.isEmpty());
         static const int column = 0;
         const QModelIndex oldIndex = q->sourceModel()->index(rowCount - 1 - difference, column, parent);
         Q_ASSERT(m_mapping.leftContains(oldIndex));
 
         const QModelIndex newIndex = q->sourceModel()->index(rowCount - 1, column, parent);
 
         QModelIndex indexAbove = oldIndex;
 
         if (start > 0) {
             // If we have something like this:
             //
             // - A
             // - - B
             // - - C
             //
             // and we then insert D as a sibling of A below it, we need to remove the mapping for A,
             // and the row number used for D must take into account the descendants of A.
 
             while (q->isSourceIndexExpanded(indexAbove) && q->sourceModel()->hasChildren(indexAbove)) {
                 Q_ASSERT(q->sourceModel()->rowCount(indexAbove) > 0);
                 indexAbove = q->sourceModel()->index(q->sourceModel()->rowCount(indexAbove) - 1, column, indexAbove);
             }
             Q_ASSERT(!q->isSourceIndexExpanded(indexAbove) || q->sourceModel()->rowCount(indexAbove) == 0);
         }
 
         Q_ASSERT(m_mapping.leftContains(indexAbove));
 
         const int newProxyRow = m_mapping.leftToRight(indexAbove) + difference;
 
         // oldIndex is E in the source. proxyRow is 4.
         m_mapping.removeLeft(oldIndex);
 
         // newIndex is J. (proxyRow + difference) is 5.
         m_mapping.insert(newIndex, newProxyRow);
     }
 
     for (int row = start; row <= end; ++row) {
         static const int column = 0;
         const QModelIndex idx = q->sourceModel()->index(row, column, parent);
         Q_ASSERT(idx.isValid());
 
         if (q->isSourceIndexExpanded(idx) && q->sourceModel()->hasChildren(idx) && q->sourceModel()->rowCount(idx) > 0) {
             m_pendingParents.append(idx);
         }
     }
 
     m_rowCount += difference;
 
     q->endInsertRows();
     scheduleProcessPendingParents();
     if (parent.isValid()) {
         const QModelIndex index = q->mapFromSource(parent);
         Q_EMIT q->dataChanged(index,
                               index,
                               {KDescendantsProxyModel::ExpandableRole, KDescendantsProxyModel::ExpandedRole, KDescendantsProxyModel::HasSiblingsRole});
     }
 
     if (start > 0) {
         notifyhasSiblings(q->sourceModel()->index(start - 1, 0, parent));
     }
 }
 
 void KDescendantsProxyModelPrivate::sourceRowsAboutToBeRemoved(const QModelIndex &parent, int start, int end)
 {
     Q_Q(KDescendantsProxyModel);
 
     if (!q->isSourceIndexExpanded(parent) || !q->isSourceIndexVisible(parent)) {
         return;
     }
 
     const int proxyStart = q->mapFromSource(q->sourceModel()->index(start, 0, parent)).row();
 
     static const int column = 0;
     QModelIndex idx = q->sourceModel()->index(end, column, parent);
     while (q->sourceModel()->hasChildren(idx) && q->sourceModel()->rowCount(idx) > 0) {
         idx = q->sourceModel()->index(q->sourceModel()->rowCount(idx) - 1, column, idx);
     }
     const int proxyEnd = q->mapFromSource(idx).row();
 
     for (int i = start; i <= end; ++i) {
         QModelIndex idx = q->sourceModel()->index(i, column, parent);
         m_expandedSourceIndexes.remove(QPersistentModelIndex(idx));
     }
 
     m_removePair = qMakePair(proxyStart, proxyEnd);
 
     q->beginRemoveRows(QModelIndex(), proxyStart, proxyEnd);
 }
 
 static QModelIndex getFirstDeepest(QAbstractItemModel *model, const QModelIndex &parent, int *count)
 {
     static const int column = 0;
     Q_ASSERT(model->hasChildren(parent));
     Q_ASSERT(model->rowCount(parent) > 0);
     for (int row = 0; row < model->rowCount(parent); ++row) {
         (*count)++;
         const QModelIndex child = model->index(row, column, parent);
         Q_ASSERT(child.isValid());
         if (model->hasChildren(child)) {
             return getFirstDeepest(model, child, count);
         }
     }
     return model->index(model->rowCount(parent) - 1, column, parent);
 }
 
 void KDescendantsProxyModelPrivate::sourceRowsRemoved(const QModelIndex &parent, int start, int end)
 {
     Q_Q(KDescendantsProxyModel);
     Q_UNUSED(end)
 
     if (!q->isSourceIndexExpanded(parent) || !q->isSourceIndexVisible(parent)) {
         if (parent.isValid()) {
             const QModelIndex index = q->mapFromSource(parent);
             Q_EMIT q->dataChanged(index, index, {KDescendantsProxyModel::ExpandableRole, KDescendantsProxyModel::ExpandedRole});
         }
         return;
     }
 
     const int rowCount = q->sourceModel()->rowCount(parent);
 
     const int proxyStart = m_removePair.first;
     const int proxyEnd = m_removePair.second;
 
     const int difference = proxyEnd - proxyStart + 1;
     {
         Mapping::right_iterator it = m_mapping.rightLowerBound(proxyStart);
         const Mapping::right_iterator endIt = m_mapping.rightUpperBound(proxyEnd);
 
         if (endIt != m_mapping.rightEnd()) {
             while (it != endIt) {
                 it = m_mapping.eraseRight(it);
             }
         } else {
             while (it != m_mapping.rightUpperBound(proxyEnd)) {
                 it = m_mapping.eraseRight(it);
             }
         }
     }
 
     m_removePair = qMakePair(-1, -1);
     m_rowCount -= difference;
     Q_ASSERT(m_rowCount >= 0);
 
     updateInternalIndexes(proxyStart, -1 * difference);
 
     if (rowCount != start || rowCount == 0) {
         q->endRemoveRows();
         if (parent.isValid()) {
             const QModelIndex index = q->mapFromSource(parent);
             Q_EMIT q->dataChanged(index, index, {KDescendantsProxyModel::ExpandableRole, KDescendantsProxyModel::ExpandedRole});
         }
         if (start > 0) {
             notifyhasSiblings(q->sourceModel()->index(start - 1, 0, parent));
         }
         return;
     }
 
     static const int column = 0;
     const QModelIndex newEnd = q->sourceModel()->index(rowCount - 1, column, parent);
     Q_ASSERT(newEnd.isValid());
 
     if (m_mapping.isEmpty()) {
         m_mapping.insert(newEnd, newEnd.row());
         q->endRemoveRows();
         if (start > 0) {
             notifyhasSiblings(q->sourceModel()->index(start - 1, 0, parent));
         }
         return;
     }
     if (q->sourceModel()->hasChildren(newEnd)) {
         int count = 0;
         const QModelIndex firstDeepest = getFirstDeepest(q->sourceModel(), newEnd, &count);
         Q_ASSERT(firstDeepest.isValid());
         const int firstDeepestProxy = m_mapping.leftToRight(firstDeepest);
 
         m_mapping.insert(newEnd, firstDeepestProxy - count);
         q->endRemoveRows();
         if (start > 0) {
             notifyhasSiblings(q->sourceModel()->index(start - 1, 0, parent));
         }
         return;
     }
     Mapping::right_iterator lowerBound = m_mapping.rightLowerBound(proxyStart);
     if (lowerBound == m_mapping.rightEnd()) {
         int proxyRow = std::prev(lowerBound).key();
 
         for (int row = newEnd.row(); row >= 0; --row) {
             const QModelIndex newEndSibling = q->sourceModel()->index(row, column, parent);
             if (!q->sourceModel()->hasChildren(newEndSibling)) {
                 ++proxyRow;
             } else {
                 break;
             }
         }
         m_mapping.insert(newEnd, proxyRow);
         q->endRemoveRows();
         if (start > 0) {
             notifyhasSiblings(q->sourceModel()->index(start - 1, 0, parent));
         }
         return;
     } else if (lowerBound == m_mapping.rightBegin()) {
         int proxyRow = rowCount - 1;
         QModelIndex trackedParent = parent;
         while (trackedParent.isValid()) {
             proxyRow += (trackedParent.row() + 1);
             trackedParent = trackedParent.parent();
         }
         m_mapping.insert(newEnd, proxyRow);
         q->endRemoveRows();
         if (start > 0) {
             notifyhasSiblings(q->sourceModel()->index(start - 1, 0, parent));
         }
         return;
     }
     const Mapping::right_iterator boundAbove = std::prev(lowerBound);
 
     QList<QModelIndex> targetParents;
     targetParents.push_back(parent);
     {
         QModelIndex target = parent;
         int count = 0;
         while (target.isValid()) {
             if (target == boundAbove.value()) {
                 m_mapping.insert(newEnd, count + boundAbove.key() + newEnd.row() + 1);
                 q->endRemoveRows();
                 if (start > 0) {
                     notifyhasSiblings(q->sourceModel()->index(start - 1, 0, parent));
                 }
                 return;
             }
             count += (target.row() + 1);
             target = target.parent();
             if (target.isValid()) {
                 targetParents.push_back(target);
             }
         }
     }
 
     QModelIndex boundParent = boundAbove.value().parent();
     QModelIndex prevParent = boundParent;
     Q_ASSERT(boundParent.isValid());
     while (boundParent.isValid()) {
         prevParent = boundParent;
         boundParent = boundParent.parent();
 
         if (targetParents.contains(prevParent)) {
             break;
         }
 
         if (!m_mapping.leftContains(prevParent)) {
             break;
         }
 
         if (m_mapping.leftToRight(prevParent) > boundAbove.key()) {
             break;
         }
     }
 
     QModelIndex trackedParent = parent;
 
     int proxyRow = boundAbove.key();
 
     Q_ASSERT(prevParent.isValid());
     proxyRow -= prevParent.row();
     while (trackedParent != boundParent) {
         proxyRow += (trackedParent.row() + 1);
         trackedParent = trackedParent.parent();
     }
     m_mapping.insert(newEnd, proxyRow + newEnd.row());
     q->endRemoveRows();
 
     if (parent.isValid()) {
         const QModelIndex oindex = q->mapFromSource(parent);
         QList<int> rolesChanged({KDescendantsProxyModel::ExpandableRole});
 
         if (!q->sourceModel()->hasChildren(parent)) {
             rolesChanged << KDescendantsProxyModel::ExpandedRole;
         } else if (q->sourceModel()->rowCount(parent) <= start) {
             const QModelIndex index = q->mapFromSource(q->sourceModel()->index(q->sourceModel()->rowCount(parent) - 1, 0, parent));
             Q_EMIT q->dataChanged(index, index, {KDescendantsProxyModel::ExpandedRole});
         }
 
         Q_EMIT q->dataChanged(oindex, oindex, rolesChanged);
     }
 
     if (start > 0) {
         notifyhasSiblings(q->sourceModel()->index(start - 1, 0, parent));
     }
 }
 
 void KDescendantsProxyModelPrivate::sourceRowsAboutToBeMoved(const QModelIndex &srcParent,
                                                              int srcStart,
                                                              int srcEnd,
                                                              const QModelIndex &destParent,
                                                              int destStart)
 {
     Q_Q(KDescendantsProxyModel);
 
     Q_UNUSED(destStart)
 
     if (q->isSourceIndexExpanded(srcParent) && q->isSourceIndexVisible(srcParent)
         && (!q->isSourceIndexExpanded(destParent) || !q->isSourceIndexVisible(destParent))) {
         const QModelIndex proxySrcParent = q->mapFromSource(srcParent);
         const int proxyParentRow = proxySrcParent.isValid() ? proxySrcParent.row() : 0;
         q->beginRemoveRows(QModelIndex(), proxyParentRow + srcStart, proxyParentRow + srcEnd);
 
     } else if ((!q->isSourceIndexExpanded(srcParent) || !q->isSourceIndexVisible(srcParent)) && q->isSourceIndexExpanded(destParent)
                && q->isSourceIndexVisible(destParent)) {
         const QModelIndex proxyDestParent = q->mapFromSource(srcParent);
         const int proxyParentRow = proxyDestParent.isValid() ? proxyDestParent.row() : 0;
 
         q->beginInsertRows(QModelIndex(), proxyParentRow + destStart, proxyParentRow + destStart + (srcEnd - srcStart));
     }
 
     sourceLayoutAboutToBeChanged();
 }
 
 void KDescendantsProxyModelPrivate::sourceRowsMoved(const QModelIndex &srcParent, int srcStart, int srcEnd, const QModelIndex &destParent, int destStart)
 {
     Q_Q(KDescendantsProxyModel);
 
     Q_UNUSED(srcParent)
     Q_UNUSED(srcStart)
     Q_UNUSED(srcEnd)
     Q_UNUSED(destParent)
     Q_UNUSED(destStart)
 
     if (q->isSourceIndexExpanded(srcParent) && q->isSourceIndexVisible(srcParent)
         && (!q->isSourceIndexExpanded(destParent) || !q->isSourceIndexVisible(destParent))) {
         q->endRemoveRows();
     } else if (!q->isSourceIndexExpanded(srcParent) && q->isSourceIndexExpanded(destParent)) {
         q->endInsertRows();
     }
 
     sourceLayoutChanged();
 
     const QModelIndex index1 = q->mapFromSource(srcParent);
     const QModelIndex index2 = q->mapFromSource(destParent);
     Q_EMIT q->dataChanged(index1, index1, {KDescendantsProxyModel::ExpandableRole});
     if (index1 != index2) {
         Q_EMIT q->dataChanged(index2, index2, {KDescendantsProxyModel::ExpandableRole});
         if (!q->sourceModel()->hasChildren(destParent)) {
             Q_EMIT q->dataChanged(index2, index2, {KDescendantsProxyModel::ExpandableRole});
         }
     }
     const QModelIndex lastIndex = q->mapFromSource(q->sourceModel()->index(q->sourceModel()->rowCount(srcParent) - 1, 0, srcParent));
     Q_EMIT q->dataChanged(lastIndex, lastIndex, {KDescendantsProxyModel::ExpandableRole});
 
     if (srcStart > 0) {
         notifyhasSiblings(q->sourceModel()->index(srcStart - 1, 0, srcParent));
     }
     if (destStart > 0) {
         notifyhasSiblings(q->sourceModel()->index(destStart - 1, 0, destParent));
     }
 }
 
 void KDescendantsProxyModelPrivate::sourceModelAboutToBeReset()
 {
     Q_Q(KDescendantsProxyModel);
     q->beginResetModel();
 }
 
 void KDescendantsProxyModelPrivate::sourceModelReset()
 {
     Q_Q(KDescendantsProxyModel);
     resetInternalData();
     if (q->sourceModel()->hasChildren() && q->sourceModel()->rowCount() > 0) {
         m_pendingParents.append(QModelIndex());
         scheduleProcessPendingParents();
     }
     q->endResetModel();
 }
 
 void KDescendantsProxyModelPrivate::sourceLayoutAboutToBeChanged()
 {
     Q_Q(KDescendantsProxyModel);
 
     if (m_ignoreNextLayoutChanged) {
         m_ignoreNextLayoutChanged = false;
         return;
     }
 
     if (m_mapping.isEmpty()) {
         return;
     }
 
     Q_EMIT q->layoutAboutToBeChanged();
 
     QPersistentModelIndex srcPersistentIndex;
     const auto lst = q->persistentIndexList();
     for (const QModelIndex &proxyPersistentIndex : lst) {
         m_proxyIndexes << proxyPersistentIndex;
         Q_ASSERT(proxyPersistentIndex.isValid());
         srcPersistentIndex = q->mapToSource(proxyPersistentIndex);
         Q_ASSERT(srcPersistentIndex.isValid());
         m_layoutChangePersistentIndexes << srcPersistentIndex;
     }
 }
 
 void KDescendantsProxyModelPrivate::sourceLayoutChanged()
 {
     Q_Q(KDescendantsProxyModel);
 
     if (m_ignoreNextLayoutAboutToBeChanged) {
         m_ignoreNextLayoutAboutToBeChanged = false;
         return;
     }
 
     if (m_mapping.isEmpty()) {
         return;
     }
 
     m_rowCount = 0;
 
     synchronousMappingRefresh();
 
     for (int i = 0; i < m_proxyIndexes.size(); ++i) {
         q->changePersistentIndex(m_proxyIndexes.at(i), q->mapFromSource(m_layoutChangePersistentIndexes.at(i)));
     }
 
     m_layoutChangePersistentIndexes.clear();
     m_proxyIndexes.clear();
 
     Q_EMIT q->layoutChanged();
 }
 
 void KDescendantsProxyModelPrivate::sourceDataChanged(const QModelIndex &topLeft, const QModelIndex &bottomRight)
 {
     Q_Q(KDescendantsProxyModel);
     // It is actually possible in a real world scenario that the source model emits dataChanged
     // with invalid indexes when the source model is a QSortFilterProxyModel
     // because QSortFilterProxyModel doesn't check for mapped index validity when its
     // source model emitted dataChanged on a column QSortFilterProxyModel doesn't accept.
     // See https://bugreports.qt.io/browse/QTBUG-86850
     if (!topLeft.isValid() || !bottomRight.isValid()) {
         return;
     }
     Q_ASSERT(topLeft.model() == q->sourceModel());
     Q_ASSERT(bottomRight.model() == q->sourceModel());
 
     if (!q->isSourceIndexExpanded(topLeft.parent()) || !q->isSourceIndexVisible(topLeft.parent())) {
         return;
     }
 
     const int topRow = topLeft.row();
     const int bottomRow = bottomRight.row();
 
     for (int i = topRow; i <= bottomRow; ++i) {
         const QModelIndex sourceTopLeft = q->sourceModel()->index(i, topLeft.column(), topLeft.parent());
 
         Q_ASSERT(sourceTopLeft.isValid());
         const QModelIndex proxyTopLeft = q->mapFromSource(sourceTopLeft);
         // TODO. If an index does not have any descendants, then we can emit in blocks of rows.
         // As it is we emit once for each row.
         const QModelIndex sourceBottomRight = q->sourceModel()->index(i, bottomRight.column(), bottomRight.parent());
         const QModelIndex proxyBottomRight = q->mapFromSource(sourceBottomRight);
         Q_ASSERT(proxyTopLeft.isValid());
         Q_ASSERT(proxyBottomRight.isValid());
         Q_EMIT q->dataChanged(proxyTopLeft, proxyBottomRight);
     }
 }
 
 void KDescendantsProxyModelPrivate::sourceModelDestroyed()
 {
     resetInternalData();
 }
 
 QMimeData *KDescendantsProxyModel::mimeData(const QModelIndexList &indexes) const
 {
     if (!sourceModel()) {
         return QAbstractProxyModel::mimeData(indexes);
     }
     Q_ASSERT(sourceModel());
     QModelIndexList sourceIndexes;
     for (const QModelIndex &index : indexes) {
         sourceIndexes << mapToSource(index);
     }
     return sourceModel()->mimeData(sourceIndexes);
 }
 
 QStringList KDescendantsProxyModel::mimeTypes() const
 {
     if (!sourceModel()) {
         return QAbstractProxyModel::mimeTypes();
     }
     Q_ASSERT(sourceModel());
     return sourceModel()->mimeTypes();
 }
 
 Qt::DropActions KDescendantsProxyModel::supportedDropActions() const
 {
     if (!sourceModel()) {
         return QAbstractProxyModel::supportedDropActions();
     }
     return sourceModel()->supportedDropActions();
 }
 
 #include "moc_kdescendantsproxymodel.cpp"