1 | /****************************************************************************
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2 | **
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3 | ** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
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4 | ** All rights reserved.
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5 | ** Contact: Nokia Corporation ([email protected])
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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 | ** $QT_BEGIN_LICENSE:BSD$
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10 | ** You may use this file under the terms of the BSD license as follows:
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11 | **
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12 | ** "Redistribution and use in source and binary forms, with or without
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13 | ** modification, are permitted provided that the following conditions are
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14 | ** met:
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15 | ** * Redistributions of source code must retain the above copyright
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16 | ** notice, this list of conditions and the following disclaimer.
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17 | ** * Redistributions in binary form must reproduce the above copyright
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18 | ** notice, this list of conditions and the following disclaimer in
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19 | ** the documentation and/or other materials provided with the
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20 | ** distribution.
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21 | ** * Neither the name of Nokia Corporation and its Subsidiary(-ies) nor
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22 | ** the names of its contributors may be used to endorse or promote
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23 | ** products derived from this software without specific prior written
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24 | ** permission.
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25 | **
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26 | ** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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27 | ** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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28 | ** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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29 | ** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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30 | ** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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31 | ** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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32 | ** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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33 | ** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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34 | ** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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35 | ** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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36 | ** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
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37 | ** $QT_END_LICENSE$
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38 | **
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39 | ****************************************************************************/
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40 | #include "randomlistmodel.h"
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41 | #include <stdlib.h>
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42 |
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43 | static const int bufferSize(500);
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44 | static const int lookAhead(100);
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45 | static const int halfLookAhead(lookAhead/2);
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46 |
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47 | RandomListModel::RandomListModel(QObject *parent)
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48 | : QAbstractListModel(parent), m_rows(bufferSize), m_count(10000)
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49 | {
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50 | }
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51 |
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52 | RandomListModel::~RandomListModel()
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53 | {
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54 | }
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55 |
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56 | int RandomListModel::rowCount(const QModelIndex &) const
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57 | {
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58 | return m_count;
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59 | }
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60 |
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61 | //! [0]
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62 | QVariant RandomListModel::data(const QModelIndex &index, int role) const
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63 | {
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64 | if (role != Qt::DisplayRole)
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65 | return QVariant();
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66 |
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67 | int row = index.row();
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68 |
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69 | if (row > m_rows.lastIndex()) {
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70 | if (row - m_rows.lastIndex() > lookAhead)
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71 | cacheRows(row-halfLookAhead, qMin(m_count, row+halfLookAhead));
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72 | else while (row > m_rows.lastIndex())
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73 | m_rows.append(fetchRow(m_rows.lastIndex()+1));
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74 | } else if (row < m_rows.firstIndex()) {
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75 | if (m_rows.firstIndex() - row > lookAhead)
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76 | cacheRows(qMax(0, row-halfLookAhead), row+halfLookAhead);
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77 | else while (row < m_rows.firstIndex())
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78 | m_rows.prepend(fetchRow(m_rows.firstIndex()-1));
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79 | }
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80 |
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81 | return m_rows.at(row);
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82 | }
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83 |
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84 | void RandomListModel::cacheRows(int from, int to) const
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85 | {
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86 | for (int i = from; i <= to; ++i)
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87 | m_rows.insert(i, fetchRow(i));
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88 | }
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89 | //![0]
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90 |
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91 | //![1]
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92 | QString RandomListModel::fetchRow(int position) const
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93 | {
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94 | return QString::number(rand() % ++position);
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95 | }
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96 | //![1]
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