source: trunk/examples/tools/contiguouscache/randomlistmodel.cpp@ 987

Last change on this file since 987 was 846, checked in by Dmitry A. Kuminov, 14 years ago

trunk: Merged in qt 4.7.2 sources from branches/vendor/nokia/qt.

  • Property svn:eol-style set to native
File size: 3.4 KB
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1/****************************************************************************
2**
3** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
4** All rights reserved.
5** Contact: Nokia Corporation ([email protected])
6**
7** This file is part of the examples of the Qt Toolkit.
8**
9** $QT_BEGIN_LICENSE:BSD$
10** You may use this file under the terms of the BSD license as follows:
11**
12** "Redistribution and use in source and binary forms, with or without
13** modification, are permitted provided that the following conditions are
14** met:
15** * Redistributions of source code must retain the above copyright
16** notice, this list of conditions and the following disclaimer.
17** * Redistributions in binary form must reproduce the above copyright
18** notice, this list of conditions and the following disclaimer in
19** the documentation and/or other materials provided with the
20** distribution.
21** * Neither the name of Nokia Corporation and its Subsidiary(-ies) nor
22** the names of its contributors may be used to endorse or promote
23** products derived from this software without specific prior written
24** permission.
25**
26** THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
27** "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
28** LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
29** A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
30** OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
31** SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
32** LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
33** DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
34** THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
35** (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
36** OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE."
37** $QT_END_LICENSE$
38**
39****************************************************************************/
40#include "randomlistmodel.h"
41#include <stdlib.h>
42
43static const int bufferSize(500);
44static const int lookAhead(100);
45static const int halfLookAhead(lookAhead/2);
46
47RandomListModel::RandomListModel(QObject *parent)
48: QAbstractListModel(parent), m_rows(bufferSize), m_count(10000)
49{
50}
51
52RandomListModel::~RandomListModel()
53{
54}
55
56int RandomListModel::rowCount(const QModelIndex &) const
57{
58 return m_count;
59}
60
61//! [0]
62QVariant RandomListModel::data(const QModelIndex &index, int role) const
63{
64 if (role != Qt::DisplayRole)
65 return QVariant();
66
67 int row = index.row();
68
69 if (row > m_rows.lastIndex()) {
70 if (row - m_rows.lastIndex() > lookAhead)
71 cacheRows(row-halfLookAhead, qMin(m_count, row+halfLookAhead));
72 else while (row > m_rows.lastIndex())
73 m_rows.append(fetchRow(m_rows.lastIndex()+1));
74 } else if (row < m_rows.firstIndex()) {
75 if (m_rows.firstIndex() - row > lookAhead)
76 cacheRows(qMax(0, row-halfLookAhead), row+halfLookAhead);
77 else while (row < m_rows.firstIndex())
78 m_rows.prepend(fetchRow(m_rows.firstIndex()-1));
79 }
80
81 return m_rows.at(row);
82}
83
84void RandomListModel::cacheRows(int from, int to) const
85{
86 for (int i = from; i <= to; ++i)
87 m_rows.insert(i, fetchRow(i));
88}
89//![0]
90
91//![1]
92QString RandomListModel::fetchRow(int position) const
93{
94 return QString::number(rand() % ++position);
95}
96//![1]
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