| 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 documentation of the Qt Toolkit.
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| 8 | **
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| 9 | ** $QT_BEGIN_LICENSE:LGPL$
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| 10 | ** Commercial Usage
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| 11 | ** Licensees holding valid Qt Commercial licenses may use this file in
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| 12 | ** accordance with the Qt Commercial License Agreement provided with the
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| 13 | ** Software or, alternatively, in accordance with the terms contained in
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| 14 | ** a written agreement between you and Nokia.
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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 | ** GNU General Public License Usage
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| 29 | ** Alternatively, this file may be used under the terms of the GNU
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| 30 | ** General Public License version 3.0 as published by the Free Software
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| 31 | ** Foundation and appearing in the file LICENSE.GPL included in the
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| 32 | ** packaging of this file. Please review the following information to
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| 33 | ** ensure the GNU General Public License version 3.0 requirements will be
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| 34 | ** met: http://www.gnu.org/copyleft/gpl.html.
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| 35 | **
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| 36 | ** If you have questions regarding the use of this file, please contact
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| 37 | ** Nokia at qt-info@nokia.com.
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| 38 | ** $QT_END_LICENSE$
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| 39 | **
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| 40 | ****************************************************************************/
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| 41 |
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| 42 | /*!
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| 43 | \example itemviews/chart
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| 44 | \title Chart Example
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| 45 |
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| 46 | The Chart example shows how to create a custom view for the model/view framework.
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| 47 |
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| 48 | \image chart-example.png
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| 49 |
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| 50 | In this example, the items in a table model are represented as slices in a pie chart,
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| 51 | relying on the flexibility of the model/view architecture to handle custom editing
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| 52 | and selection features.
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| 53 |
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| 54 | \bold{Note that you only need to create a new view class if your data requires a
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| 55 | specialized representation.} You should first consider using a standard QListView,
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| 56 | QTableView, or QTreeView with a custom QItemDelegate subclass if you need to
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| 57 | represent data in a special way.
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| 58 |
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| 59 | \omit
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| 60 | \section1 PieView Class Definition
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| 61 |
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| 62 | The \c PieView class is a subclass of QAbstractItemView. The base class provides
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| 63 | much of the functionality required by view classes, so we only need to provide
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| 64 | implementations for three public functions: visualRect(), scrollTo(), and
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| 65 | indexAt(). However, the view needs to maintain strict control over its look and
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| 66 | feel, so we also provide implementations for a number of other functions:
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| 67 |
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| 68 | \snippet examples/itemviews/chart/pieview.h 0
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| 69 |
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| 70 |
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| 71 |
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| 72 | \section1 PieView Class Implementation
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| 73 |
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| 74 | The paint event renders the data from the standard item model as a pie chart.
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| 75 | We interpret the data in the following way:
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| 76 |
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| 77 | \list
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| 78 | \o Column 0 contains data in two different roles:
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| 79 | The \l{Qt::ItemDataRole}{DisplayRole} contains a label, and the
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| 80 | \l{Qt::ItemDataRole}{DecorationRole} contains the color of the pie slice.
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| 81 | \o Column 1 contains a quantity which we will convert to the angular extent of
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| 82 | the slice.
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| 83 | \endlist
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| 84 |
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| 85 | The figure is always drawn with the chart on the left and the key on
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| 86 | the right. This means that we must try and obtain an area that is wider
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| 87 | than it is tall. We do this by imposing a particular aspect ratio on
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| 88 | the chart and applying it to the available vertical space. This ensures
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| 89 | that we always obtain the maximum horizontal space for the aspect ratio
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| 90 | used.
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| 91 | We also apply fixed size margin around the figure.
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| 92 |
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| 93 | We use logical coordinates to draw the chart and key, and position them
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| 94 | on the view using viewports.
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| 95 | \endomit
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| 96 | */
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