Create the Sorter class

SortFilterProxyModel.pri

@@ -3,6 +3,8 @@
 INCLUDEPATH += $$PWD
 
 HEADERS += $$PWD/qqmlsortfilterproxymodel.h \
-    $$PWD/filter.h
+    $$PWD/filter.h \
+    $$PWD/sorter.h
 SOURCES += $$PWD/qqmlsortfilterproxymodel.cpp \
-    $$PWD/filter.cpp
+    $$PWD/filter.cpp \
+    $$PWD/sorter.cpp

sorter.cpp

@@ -0,0 +1,81 @@
+#include "sorter.h"
+#include <QtQml>
+
+namespace qqsfpm {
+
+Sorter::Sorter(QObject *parent) : QObject(parent)
+{
+    connect(this, &Sorter::sorterChanged, this, &Sorter::onSorterChanged);
+}
+
+Sorter::~Sorter() = default;
+
+bool Sorter::enabled() const
+{
+    return m_enabled;
+}
+
+void Sorter::setEnabled(bool enabled)
+{
+    if (m_enabled == enabled)
+        return;
+
+    m_enabled = enabled;
+    emit enabledChanged();
+    emit sorterChanged();
+}
+
+bool Sorter::ascendingOrder() const
+{
+    return m_ascendingOrder;
+}
+
+void Sorter::setAscendingOrder(bool ascendingOrder)
+{
+    if (m_ascendingOrder == ascendingOrder)
+        return;
+
+    m_ascendingOrder = ascendingOrder;
+    emit ascendingOrderChanged();
+    emit sorterChanged();
+}
+
+int Sorter::compareRows(const QModelIndex &source_left, const QModelIndex &source_right) const
+{
+    int comparison = compare(source_left, source_right);
+    return m_ascendingOrder ? comparison : -comparison;
+}
+
+QQmlSortFilterProxyModel* Sorter::proxyModel() const
+{
+    return m_proxyModel;
+}
+
+int Sorter::compare(const QModelIndex &sourceLeft, const QModelIndex &sourceRight) const
+{
+    if (lessThan(sourceLeft, sourceRight))
+        return -1;
+    if (lessThan(sourceRight, sourceLeft))
+        return 1;
+    return 0;
+}
+
+bool Sorter::lessThan(const QModelIndex &sourceLeft, const QModelIndex &sourceRight) const
+{
+    Q_UNUSED(sourceLeft)
+    Q_UNUSED(sourceRight)
+    return false;
+}
+
+void Sorter::proxyModelCompleted()
+{
+
+}
+
+void Sorter::onSorterChanged()
+{
+    if (m_enabled)
+        emit invalidate();
+}
+
+}

sorter.h

@@ -0,0 +1,53 @@
+#ifndef SORTER_H
+#define SORTER_H
+
+#include <QObject>
+#include "qqmlsortfilterproxymodel.h"
+
+namespace qqsfpm {
+
+class Sorter : public QObject
+{
+    Q_OBJECT
+    Q_PROPERTY(bool enabled READ enabled WRITE setEnabled NOTIFY enabledChanged)
+    Q_PROPERTY(bool ascendingOrder READ ascendingOrder WRITE setAscendingOrder NOTIFY ascendingOrderChanged)
+    friend class QQmlSortFilterProxyModel;
+
+public:
+    Sorter(QObject* parent = nullptr);
+    virtual ~Sorter() = 0;
+
+    bool enabled() const;
+    void setEnabled(bool enabled);
+
+    bool ascendingOrder() const;
+    void setAscendingOrder(bool ascendingOrder);
+
+    int compareRows(const QModelIndex& source_left, const QModelIndex& source_right) const;
+
+signals:
+    void enabledChanged();
+    void ascendingOrderChanged();
+
+    void sorterChanged();
+    void invalidate();
+
+protected:
+    QQmlSortFilterProxyModel* proxyModel() const;
+
+    virtual int compare(const QModelIndex& sourceLeft, const QModelIndex& sourceRight) const;
+    virtual bool lessThan(const QModelIndex& sourceLeft, const QModelIndex& sourceRight) const;
+    virtual void proxyModelCompleted();
+
+private slots:
+    void onSorterChanged();
+
+private:
+    bool m_enabled = true;
+    bool m_ascendingOrder = true;
+    QQmlSortFilterProxyModel* m_proxyModel = nullptr;
+};
+
+}
+
+#endif // SORTER_H