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1 /**************************************************************************** |
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2 ** |
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3 ** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). |
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4 ** All rights reserved. |
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5 ** Contact: Nokia Corporation (qt-info@nokia.com) |
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6 ** |
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7 ** This file is part of the examples of the Qt Toolkit. |
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8 ** |
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9 ** $QT_BEGIN_LICENSE:LGPL$ |
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10 ** No Commercial Usage |
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11 ** This file contains pre-release code and may not be distributed. |
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12 ** You may use this file in accordance with the terms and conditions |
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13 ** contained in the Technology Preview License Agreement accompanying |
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14 ** this package. |
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15 ** |
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16 ** GNU Lesser General Public License Usage |
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17 ** Alternatively, this file may be used under the terms of the GNU Lesser |
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18 ** General Public License version 2.1 as published by the Free Software |
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19 ** Foundation and appearing in the file LICENSE.LGPL included in the |
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20 ** packaging of this file. Please review the following information to |
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21 ** ensure the GNU Lesser General Public License version 2.1 requirements |
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22 ** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html. |
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23 ** |
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24 ** In addition, as a special exception, Nokia gives you certain additional |
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25 ** rights. These rights are described in the Nokia Qt LGPL Exception |
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26 ** version 1.1, included in the file LGPL_EXCEPTION.txt in this package. |
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27 ** |
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28 ** If you have questions regarding the use of this file, please contact |
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29 ** Nokia at qt-info@nokia.com. |
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30 ** |
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31 ** |
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32 ** |
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33 ** |
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34 ** |
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35 ** |
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36 ** |
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37 ** |
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38 ** $QT_END_LICENSE$ |
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39 ** |
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40 ****************************************************************************/ |
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41 #include "randomlistmodel.h" |
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42 #include <stdlib.h> |
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43 |
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44 static const int bufferSize(500); |
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45 static const int lookAhead(100); |
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46 static const int halfLookAhead(lookAhead/2); |
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47 |
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48 RandomListModel::RandomListModel(QObject *parent) |
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49 : QAbstractListModel(parent), m_rows(bufferSize), m_count(10000) |
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50 { |
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51 } |
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52 |
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53 RandomListModel::~RandomListModel() |
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54 { |
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55 } |
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56 |
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57 int RandomListModel::rowCount(const QModelIndex &) const |
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58 { |
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59 return m_count; |
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60 } |
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61 |
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62 //! [0] |
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63 QVariant RandomListModel::data(const QModelIndex &index, int role) const |
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64 { |
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65 if (role != Qt::DisplayRole) |
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66 return QVariant(); |
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67 |
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68 int row = index.row(); |
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69 |
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70 if (row > m_rows.lastIndex()) { |
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71 if (row - m_rows.lastIndex() > lookAhead) |
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72 cacheRows(row-halfLookAhead, qMin(m_count, row+halfLookAhead)); |
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73 else while (row > m_rows.lastIndex()) |
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74 m_rows.append(fetchRow(m_rows.lastIndex()+1)); |
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75 } else if (row < m_rows.firstIndex()) { |
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76 if (m_rows.firstIndex() - row > lookAhead) |
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77 cacheRows(qMax(0, row-halfLookAhead), row+halfLookAhead); |
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78 else while (row < m_rows.firstIndex()) |
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79 m_rows.prepend(fetchRow(m_rows.firstIndex()-1)); |
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80 } |
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81 |
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82 return m_rows.at(row); |
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83 } |
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84 |
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85 void RandomListModel::cacheRows(int from, int to) const |
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86 { |
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87 for (int i = from; i <= to; ++i) |
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88 m_rows.insert(i, fetchRow(i)); |
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89 } |
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90 //![0] |
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91 |
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92 //![1] |
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93 QString RandomListModel::fetchRow(int position) const |
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94 { |
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95 return QString::number(rand() % ++position); |
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96 } |
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97 //![1] |