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Diffstat (limited to 'examples/tools/contiguouscache/randomlistmodel.cpp')
-rw-r--r-- | examples/tools/contiguouscache/randomlistmodel.cpp | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/examples/tools/contiguouscache/randomlistmodel.cpp b/examples/tools/contiguouscache/randomlistmodel.cpp new file mode 100644 index 0000000..b1c7204 --- /dev/null +++ b/examples/tools/contiguouscache/randomlistmodel.cpp @@ -0,0 +1,97 @@ +/**************************************************************************** +** +** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). +** Contact: Qt Software Information (qt-info@nokia.com) +** +** This file is part of the examples of the Qt Toolkit. +** +** $QT_BEGIN_LICENSE:LGPL$ +** No Commercial Usage +** This file contains pre-release code and may not be distributed. +** You may use this file in accordance with the terms and conditions +** contained in the either Technology Preview License Agreement or the +** Beta Release License Agreement. +** +** GNU Lesser General Public License Usage +** Alternatively, this file may be used under the terms of the GNU Lesser +** General Public License version 2.1 as published by the Free Software +** Foundation and appearing in the file LICENSE.LGPL included in the +** packaging of this file. Please review the following information to +** ensure the GNU Lesser General Public License version 2.1 requirements +** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. +** +** In addition, as a special exception, Nokia gives you certain +** additional rights. These rights are described in the Nokia Qt LGPL +** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this +** package. +** +** GNU General Public License Usage +** Alternatively, this file may be used under the terms of the GNU +** General Public License version 3.0 as published by the Free Software +** Foundation and appearing in the file LICENSE.GPL included in the +** packaging of this file. Please review the following information to +** ensure the GNU General Public License version 3.0 requirements will be +** met: http://www.gnu.org/copyleft/gpl.html. +** +** If you are unsure which license is appropriate for your use, please +** contact the sales department at qt-sales@nokia.com. +** $QT_END_LICENSE$ +** +****************************************************************************/ +#include "randomlistmodel.h" +#include <stdlib.h> + +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(rand() % ++position); +} +//![1] |