/**************************************************************************** ** ** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). ** Contact: Nokia Corporation (qt-info@nokia.com) ** ** This file is part of the documentation 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 http://www.qtsoftware.com/contact. ** $QT_END_LICENSE$ ** ****************************************************************************/ /*! \example itemviews/chart \title Chart Example The Chart example shows how to create a custom view for the model/view framework. \image chart-example.png In this example, the items in a table model are represented as slices in a pie chart, relying on the flexibility of the model/view architecture to handle custom editing and selection features. \bold{Note that you only need to create a new view class if your data requires a specialized representation.} You should first consider using a standard QListView, QTableView, or QTreeView with a custom QItemDelegate subclass if you need to represent data in a special way. \omit \section1 PieView Class Definition The \c PieView class is a subclass of QAbstractItemView. The base class provides much of the functionality required by view classes, so we only need to provide implementations for three public functions: visualRect(), scrollTo(), and indexAt(). However, the view needs to maintain strict control over its look and feel, so we also provide implementations for a number of other functions: \snippet examples/itemviews/chart/pieview.h 0 \section1 PieView Class Implementation The paint event renders the data from the standard item model as a pie chart. We interpret the data in the following way: \list \o Column 0 contains data in two different roles: The \l{Qt::ItemDataRole}{DisplayRole} contains a label, and the \l{Qt::ItemDataRole}{DecorationRole} contains the color of the pie slice. \o Column 1 contains a quantity which we will convert to the angular extent of the slice. \endlist The figure is always drawn with the chart on the left and the key on the right. This means that we must try and obtain an area that is wider than it is tall. We do this by imposing a particular aspect ratio on the chart and applying it to the available vertical space. This ensures that we always obtain the maximum horizontal space for the aspect ratio used. We also apply fixed size margin around the figure. We use logical coordinates to draw the chart and key, and position them on the view using viewports. \endomit */