qt 6.5.1 original

examples/corelib/tools/contiguouscache/CMakeLists.txt

@@ -0,0 +1,37 @@
+# Copyright (C) 2022 The Qt Company Ltd.
+# SPDX-License-Identifier: BSD-3-Clause
+
+cmake_minimum_required(VERSION 3.16)
+project(contiguouscache LANGUAGES CXX)
+
+if(NOT DEFINED INSTALL_EXAMPLESDIR)
+    set(INSTALL_EXAMPLESDIR "examples")
+endif()
+
+set(INSTALL_EXAMPLEDIR "${INSTALL_EXAMPLESDIR}/corelib/tools/contiguouscache")
+
+find_package(Qt6 REQUIRED COMPONENTS Core Gui Widgets)
+
+qt_standard_project_setup()
+
+qt_add_executable(contiguouscache
+    main.cpp
+    randomlistmodel.cpp randomlistmodel.h
+)
+
+set_target_properties(contiguouscache PROPERTIES
+    WIN32_EXECUTABLE TRUE
+    MACOSX_BUNDLE TRUE
+)
+
+target_link_libraries(contiguouscache PRIVATE
+    Qt6::Core
+    Qt6::Gui
+    Qt6::Widgets
+)
+
+install(TARGETS contiguouscache
+    RUNTIME DESTINATION "${INSTALL_EXAMPLEDIR}"
+    BUNDLE DESTINATION "${INSTALL_EXAMPLEDIR}"
+    LIBRARY DESTINATION "${INSTALL_EXAMPLEDIR}"
+)

examples/corelib/tools/contiguouscache/contiguouscache.pro

@@ -0,0 +1,10 @@
+QT += widgets
+requires(qtConfig(listview))
+
+HEADERS       = randomlistmodel.h
+SOURCES       = randomlistmodel.cpp \
+                main.cpp
+
+# install
+target.path = $$[QT_INSTALL_EXAMPLES]/corelib/tools/contiguouscache
+INSTALLS += target

examples/corelib/tools/contiguouscache/main.cpp

@@ -0,0 +1,18 @@
+// Copyright (C) 2016 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+
+#include "randomlistmodel.h"
+#include <QListView>
+#include <QApplication>
+
+int main(int c, char **v)
+{
+    QApplication a(c, v);
+
+    QListView view;
+    view.setUniformItemSizes(true);
+    view.setModel(new RandomListModel(&view));
+    view.show();
+
+    return a.exec();
+}

examples/corelib/tools/contiguouscache/randomlistmodel.cpp

@@ -0,0 +1,59 @@
+// Copyright (C) 2016 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+#include "randomlistmodel.h"
+#include <QRandomGenerator>
+
+static const int bufferSize(500);
+static const int lookAhead(100);
+static const int halfLookAhead(lookAhead/2);
+
+RandomListModel::RandomListModel(QObject *parent)
+: QAbstractListModel(parent), m_rows(bufferSize), m_count(10000)
+{
+}
+
+RandomListModel::~RandomListModel()
+{
+}
+
+int RandomListModel::rowCount(const QModelIndex &) const
+{
+    return m_count;
+}
+
+//! [0]
+QVariant RandomListModel::data(const QModelIndex &index, int role) const
+{
+    if (role != Qt::DisplayRole)
+        return QVariant();
+
+    int row = index.row();
+
+    if (row > m_rows.lastIndex()) {
+        if (row - m_rows.lastIndex() > lookAhead)
+            cacheRows(row-halfLookAhead, qMin(m_count, row+halfLookAhead));
+        else while (row > m_rows.lastIndex())
+            m_rows.append(fetchRow(m_rows.lastIndex()+1));
+    } else if (row < m_rows.firstIndex()) {
+        if (m_rows.firstIndex() - row > lookAhead)
+            cacheRows(qMax(0, row-halfLookAhead), row+halfLookAhead);
+        else while (row < m_rows.firstIndex())
+            m_rows.prepend(fetchRow(m_rows.firstIndex()-1));
+    }
+
+    return m_rows.at(row);
+}
+
+void RandomListModel::cacheRows(int from, int to) const
+{
+    for (int i = from; i <= to; ++i)
+        m_rows.insert(i, fetchRow(i));
+}
+//![0]
+
+//![1]
+QString RandomListModel::fetchRow(int position) const
+{
+    return QString::number(QRandomGenerator::global()->bounded(++position));
+}
+//![1]

examples/corelib/tools/contiguouscache/randomlistmodel.h

@@ -0,0 +1,29 @@
+// Copyright (C) 2016 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR BSD-3-Clause
+#ifndef RANDOMLISTMODEL_H
+#define RANDOMLISTMODEL_H
+
+#include <QContiguousCache>
+#include <QAbstractListModel>
+
+QT_FORWARD_DECLARE_CLASS(QTimer)
+
+class RandomListModel : public QAbstractListModel
+{
+    Q_OBJECT
+public:
+    RandomListModel(QObject *parent = nullptr);
+    ~RandomListModel();
+
+    int rowCount(const QModelIndex & = QModelIndex()) const override;
+    QVariant data(const QModelIndex &, int) const override;
+
+private:
+    void cacheRows(int, int) const;
+    QString fetchRow(int) const;
+
+    mutable QContiguousCache<QString> m_rows;
+    const int m_count;
+};
+
+#endif