path: root/doc/src/tutorials/modelview.qdoc

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/*!
    \page modelview.html

    \startpage {index.html}{Qt Reference Documentation}
    \nextpage {modelview-part1.html}{Introduction}

    \title Model/View Contents
    \brief An introduction to ModelView programming

    This tutorial gives an introduction to ModelView programming using the Qt
    cross-platform framework.

    \image treeview.png

    \omit
    It doesn't cover everything; the emphasis is on teaching the programming
    philosophy of Model/View programming, and Qt's features are introduced as
    needed. Some commonly used features are never used in this tutorial.
    \endomit

    In the process, we will learn about some basic technologies provided by Qt,
    such as:

    \list
    \o The difference between standard and model/view widgets
    \o Adapters betweeen forms and models
    \o Developing a simple model/view application
    \o Intermediate topics such as:
      \list
      \o Tree views
      \o Selection
      \o Predefined models
      \o Delegates
      \o Debugging with model test
      \endlist
    \endlist

    If you are completely new to Qt, please read \l{How to Learn Qt} if you
    have not already done so.

    The tutorial's source code is located in Qt's \c examples/tutorials/modelview
    directory.

    \list 1
    \o \l{modelview-part1.html}{Introduction}
    \o \l{modelview-part2.html}{Developing a Simple Model/View Application}
    \o \l{modelview-part3.html}{Intermediate Topics}
    \o \l{modelview-part4.html}{Good Sources of Additional Information}
    \endlist


*/

/*!
    \page modelview-part1.html
    \contentspage {modelview.html}{Model/View Contents}
    \previouspage {modelview.html}{Model/View Contents}
    \nextpage {modelview-part2.html}{Developing a Simple Model/View Application}
    \title An Introduction to Model/View Programming

    \section1 1. Introduction

    Model/View is a technology used to separate data from views in widgets that
    handle data sets. Standard widgets are not designed for separating data
    from views and this is why Qt 4 has two different types of widgets. Both
    types of widgets look the same, but they interact with data differently.

    \table
        \row
            \o  Standard widgets use data that is part of the widget.
            \o  \image standardwidget.png
        \row
            \o  View classes operate on external data (the model)
            \o  \image modelview.png
    \endtable

    \section2 1.1 Standard Widgets

    Let's have a closer look at a standard table widget. A table widget is a 2D
    array of the data elements that the user can change. The table widget can
    be integrated into a program flow by reading and writing the data elements
    that the table widget provides. This method is very intuitive and useful in
    many applications.

    Displaying and editing a database table with a standard table widget can be
    problematic. Two copies of the data have to be coordinated: one outside the
    widget; one inside the widget. The developer needs to know where up-to-date
    data is so the both copies contain the most recent data. The tight coupling
    of presentation and data makes it harder to write unit tests.

    \section2 1.2 Model/View to the Rescue

    Model/view stepped up to provide a solution that uses a more versatile
    architecture. Model/view eliminates the data consistency problems that may
    occur with standard widgets. Model/view also makes it easier to use more
    than one view of the same data because one model can be passed on to many
    views. The most important difference is that model/view widgets do not
    store data behind the table cells. In fact, they operate directly from your
    data. Since view classes do not know your data's structure, you need to
    provide a wrapper to make your data conform to the QAbstractItemModel
    interface. A view uses this interface to read from and write to your data
    and any class that implements QAbstractItemModel is a model. Once the view
    receives a pointer to a model, it will read and display its content and be
    its editor.

    \section2 1.3 Overview of the Model/View Widgets

    Here is an overview of the model/view widgets and their corresponding
    standard widgets.

    \table
        \header
            \o  Widget
            \o  Standard Widget (a convenience class with data in
                the widget)
            \o  Model/View View Class (for use with external data)
        \row
            \o  \inlineimage listview.png
            \o  \l QListWidget
            \o  \l QListView
        \row
            \o  \inlineimage tableview.png
            \o  \l QTableWidget
            \o  \l QTableView
        \row
            \o  \inlineimage treeview.png
            \o  \l QTreeWidget
            \o  \l QTreeView
        \row
            \o  \inlineimage columnview.png
            \o
            \o  \l QColumnView shows a tree as a hierarchy of lists
        \row
            \o  \inlineimage combobox.png
            \o {2, 1} \l QComboBox can work as both a view class and also
                      as a traditional widget
    \endtable

    \section2 1.4 Using Adapters between Forms and Models

    Having adapters between forms and models can come in handy.

    We often prefer editing data stored in tables (e.g. in database tables) in
    forms rather than in tables. There is no direct model/view counterpart for
    separating data and views for widgets that operate on one value instead of
    a dataset, so we need an adapter in order to connect the form to the source
    of data.

    \l QDataWidgetMapper is a great solution because it maps form widgets to a
    table row and it makes it very easy to build forms for database tables.

    \image widgetmapper.png

    Another example of an adapter is QCompleter. Qt has QCompleter for
    providing auto-completions in Qt widgets such as QComboBox and, as shown
    below, QLineEdit. QCompleter uses a model as its data source, so QCompleter,
    in itself, is a very handy adapter.

    \image qcompleter.png
*/

/*!
    \page modelview-part2-main-cpp.html
    \title main.cpp
    \quotefile tutorials/modelview/1_readonly/main.cpp
*/

/*!
    \page modelview-part2.html
    \contentspage {modelview-index.html}{Model/View Contents}
    \previouspage {modelview-part1.html}{Introduction}
    \nextpage {modelview-part3.html}{Intermediate Topics}
    \title Model/View Chapter 2 - A Simple Model/View Application

    \section1 2. A Simple Model/View Application

    If you want to develop a model/view application, where should you start? We
    recommend starting with a simple example and extending it step-by-step.
    This makes understanding the architecture a lot easier. Trying to
    understand the model/view architecture in detail before invoking the IDE
    has proven to be less convenient for many developers. It is substantially
    easier to start with a simple model/view application that has demo data.
    Give it a try! Simply replace the data in the examples below with your own.

    Below are 7 very simple and independent applications that show different
    sides of model/view programming. The source code can be found inside the
    \c{examples/tutorials/modelview} directory.

    \section2 2.1 A Read Only Table

    We start with an application that uses a QTableView to show data. We will
    add editing capabilities later. 

    \snippet examples/tutorials/modelview/1_readonly/main.cpp Quoting ModelView Tutorial

    We have the usual \l {modelview-part2-main-cpp.html}{main()} function:

    \snippet examples/tutorials/modelview/1_readonly/modelview.h Quoting ModelView Tutorial

    The application is a \l QMainWindow that holds a \l QTableView.  

    \snippet examples/tutorials/modelview/1_readonly/modelview.cpp Quoting ModelView Tutorial

    Here is the interesting part: We use
    \l{QTableView::setModel()}{tableView->setModel(new MyModel(this));} to
    instantiate the Model and pass its pointer to \l {QTableView}{tableView()}.
    \l{QTableView}{tableView} will invoke the methods of the pointer it has
    received to find out two things:

    \list
       \o   How many rows and columns should be displayed
       \o   What content should be printed into each cell.
    \endlist

    The model needs some code to respond to this. 

    We have a table data set, so let's start with QAbstractTableModel since it
    is easier to use.

    \snippet examples/tutorials/modelview/1_readonly/mymodel.h Quoting ModelView Tutorial

    QAbstractTableModel requires the implementation of three abstract methods.

    \snippet examples/tutorials/modelview/1_readonly/mymodel.cpp Quoting ModelView Tutorial

    The number of rows and columns is set by
    \l{QAbstractItemModel::rowCount()}{MyModel::rowCount()} and
    \l{QAbstractItemModel::columnCount()}{MyModel::columnCount()}.
    When the view has to know what the cell's text is, it calls the method.
    Row and column information is specified with parameter \c index and the
    role is set to \l{Qt::ItemDataRole}{Qt::DisplayRole}. Other roles are
    covered in the next section. In our example, the data that should be
    displayed is generated. In a real application, \c MyModel would have a
    member called \c MyData, which serves as the target for all reading and
    writing operations. 

    This small example demonstrates the passive nature of a model. The model
    does not know when it will be used or which data is needed. It simply
    provides data each time the view requests it. 

    What happens when the model 's data needs to be changed? How does the view
    know when data changes and needs to be read again? The model has to emit a
    signal that indicates what range of cells has changed.  This will be
    demonstrated in section 2.3.

    \section2 2.2 Extending the Read Only Example with Roles

    In addition to controlling what text the view displays, the model also
    controls the text's appearance. When we slightly change the model, we get
    the following result: \image readonlytable_role.png

    In fact, nothing except for the \l{QAbstractItemModel::}{data()}
    method needs to be changed to set fonts, background colour, alignment and a
    checkbox.
    Here is the \l{QAbstractItemModel::data()}{data()} method that produces the
    result shown above:

    \snippet examples/tutorials/modelview/2_formatting/mymodel.cpp Quoting ModelView Tutorial

    Each formatting property will be requested from the model with a separate
    call to the \l{QAbstractItemModel::data()}{data()} method. The \c role
    parameter is used to let the model know which property is being requested:

    \table
        \header
            \o  Role (enum Qt::ItemDataRole )
            \o  Meaning
            \o  Type 
        \row
            \o  \l{Qt::ItemDataRole}{Qt::DisplayRole}
            \o  text
            \o  QString
        \row
            \o  Qt::FontRole
            \o  font
            \o  QFont
        \row
            \o  Qt::BackgroundRole
            \o  brush for the background of the cell
            \o  QBrush
        \row
            \o  Qt::TextAlignmentRole
            \o  text alignment
            \o  enum Qt::AlignmentFlag
        \row
        \o {1, 3} Qt::CheckStateRole
        \o {1, 3} suppresses checkboxes with \l{QVariant}{QVariant()},
                  sets checkboxes with Qt::Checked or Qt::Unchecked
        \o {1, 3} \l{Qt::ItemDataRole}{enum Qt::ItemDataRole}
    \endtable

    Refer to the Qt namespace documentation to learn more about the
    Qt::ItemDataRole enum's capabilities.

    Now we need to determine how using a seperated model impacts the
    application's performance, so let's trace how often the view calls the
    \l{QAbstractItemModel::}{data()} method. In order to track how often
    the view calls the model, we have put a debug statement in the
    \l{QAbstractItemModel::}{data()} method, which logs onto stdio. In
    our small example, \l{QAbstractItemModel::}{data()} will be called 42
    times.
    Each time you hover the cursor over the field,
    \l{QAbstractItemModel::}{data()} will be called again \mdash 7 times for
    each cell. That's why it is important to make sure that your data is
    available when \l{QAbstractItemModel::}{data()} is invoked and expensive
    lookup operations are cached.

    \section2 2.3 A Clock inside a Table Cell

    \image clock.png

    We still have a read only table, but this time the content changes every
    second because we are showing the current time.

    \snippet examples/tutorials/modelview/3_changingmodel/mymodel.cpp quoting mymodel_QVariant

    Something is missing to make the clock tick. We need to tell the view every
    second that the time has changed and that it needs to be read again. We do
    this with a timer. In the constructor, we set its interval to 1 second and
    connect its timeout signal.

    \snippet examples/tutorials/modelview/3_changingmodel/mymodel.cpp quoting mymodel_a

    Here is the corresponding slot:

    \snippet examples/tutorials/modelview/3_changingmodel/mymodel.cpp quoting mymodel_b

    We ask the view to read the data in the top left cell again by emitting the
    \l{QAbstractItemModel::}{dataChanged()} signal.  Note that we did not
    explicitly connect the \l{QAbstractItemModel::}{dataChanged()} signal to
    the view. This happened automatically when we called
    \l{QTableView::}{setModel()}.

    \section2 2.4 Setting up Headers for Columns and Rows

    Headers can be hidden via a view method: \c{tableView->verticalHeader()->hide();}
    \image header.png

    The header content, however, is set via the model, so we reimplement the
    \l{QAbstractItemModel::headerData()}{headerData()} method:

    \snippet examples/tutorials/modelview/4_headers/mymodel.cpp quoting mymodel_c


    \section2 2.5 The Minimal Editing Example

    In this example, we are going to build an application that automatically
    populates a window title with content by repeating values entered into
    table cells.

    The model decides whether editing capabilities are available . We only have
    to modify the model in order for the available editing capabilities to be
    enabled. This is done by reimplementing the following virtual methods:
    \l{QAbstractItemModel::}{setData()} and \l{QAbstractItemModel::}{flags()}.

    \snippet examples/tutorials/modelview/5_edit/mymodel.h Quoting ModelView Tutorial

    We use \c QStringList m_gridData to store our data. This makes
    \c m_gridData the core of MyModel.  The rest of \c MyModel acts like a
    wrapper and adapts \c m_gridData to the  QAbstractItemModel interface. We
    have also introduced the \c editCompleted() signal,
    which makes it possible to transfer the modified text to the window title.

    \snippet examples/tutorials/modelview/5_edit/mymodel.cpp quoting mymodel_d

    In the constructor, we fill \c QStringList gridData with 6 items (one item
    for every field in the table):

    \snippet examples/tutorials/modelview/5_edit/mymodel.cpp quoting mymodel_e

    \l{QAbstractItemModel::setData()}{setData()} will be called each time the
    user edits a cell. The \c index parameter tells us which field has been
    edited and \c value  provides the result of the editing process. The role
    will always be set to \c Qt::EditRole because our cells only contain text.
    If a checkbox were present and user permissions are set to allow the
    checkbox to be selected, calls would also be made with the role set to
    \c Qt::CheckStateRole.

    \snippet examples/tutorials/modelview/5_edit/mymodel.cpp quoting mymodel_f

    Various properties of a cell can be adjusted with
    \l{QAbstractItemModel::flags()}{flags()}. Returning
    \c Qt::ItemIsEditable | \c Qt::ItemIsEnabled is enough to show an editor
    that a cell has been selected. If editing one cell modifies more data than
    the data in that particular cell, the model must emit a
    \l{QAbstractItemModel::}{dataChanged()} signal in order for the data that
    has been changed to be read.
*/

/*!
    \page modelview-part3.html
    \contentspage {modelview-index.html}{Model/View Contents}
    \previouspage {modelview-part2.html}{Developing a Simple Model/View Application}
    \nextpage {modelview-part4.html}{Good Sources of Additional Information}
    \title Model/View Chapter 3 - Intermediate Topics

    \section1 3. Intermediate Topics

    \section2 3.1 TreeView

    You can convert the example above into an application with a tree view.
    Simply replace QTableView with QTreeView, which results in a read/write
    tree. No changes have to be made to the model. The tree won't have any
    hierarchies because there aren't any hierarchies in the model itself.
    \image dummy_tree.png


    QListView, QTableView and QTreeView all use a model abstraction, which is a
    merged list, table and tree. This makes it possible to use several different
    types of view classes from the same model.
    \image list_table_tree.png


    This is how our example model looks so far:
    \image example_model.png


    We want to present a real tree. We have wrapped our data in the examples
    above in order to make a model. This time we use QStandardItemModel, which
    is a container for hierarchical data that also implements
    QAbstractItemModel. To show a tree, QStandardItemModel must be populated
    with \l{QStandardItem}{QStandardItems}, which are able to hold all the
    standard properties of items like text, fonts, checkboxes or brushes.
    \image tree_2_with_algorithm.png

    \snippet examples/tutorials/modelview/6_treeview/modelview.cpp Quoting ModelView Tutorial

    We simply instantiate a QStandardItemModel and add a couple of
    \l{QStandardItem}{QStandardItems} to the constructor. We can then make a
    hierarchical data structure because a QStandardItem can hold other
    \l{QStandardItem}{QStandardItems}. Nodes are collapsed and expanded within
    the view.

    \section2 3.2 Working with Selections

    We want to access a selected item's content in order to output it into the
    window title together with the hierarchy level.
    \image selection2.png

    So let's create a couple of items:

    \snippet examples/tutorials/modelview/7_selections/modelview.cpp quoting modelview_a

    Views manage selections within a separate selection model, which can be
    retrieved with the \l{QAbstractItemView::}{selectionModel()}
    method. We retrieve the selection Model in order to connect a slot to its
    \l{QAbstractItemView::}{selectionChanged()} signal.

    \snippet examples/tutorials/modelview/7_selections/modelview.cpp quoting modelview_b

    We get the model index that corresponds to the selection by calling 
    \l{QItemSelectionModel::currentIndex()}{treeView->selectionModel()->currentIndex()}
    and we get the the field's string by using the model index. Then we just
    calculate the item's \c hierarchyLevel.  Top level items do not have
    parents and the \l{QAbstractItemModel::}{parent()} method will return a
    default constructed \l{QModelIndex}{QModelIndex()}. This is why we use the
    \l{QAbstractItemModel::}{parent()} method to iterate to the top level while
    counting the steps performed during iteration.

    The selection model (as shown above) can be retrieved, but it can also be
    set with \l{QAbstractItemView}{QAbstractItemView::setSelectionModel}. This
    is how it's possible to have 3 view classes with synchronised selections
    because only one instance of a selection model is used. The instance of a
    selection model is retrieved from the first view class with
    \l{QAbstractItemView::}{selectionModel()} and the result is assigned to the
    second and third view class with \l{QAbstractItemView::}{setSelectionModel()}.

    \section2 3.3 Predefined Models

    The typical way to use model/view is to wrap specific data to make it
    usable with view classes. Qt, however, also provides predefined models for
    common underlying data structures. If one of the available data structures
    is suitable for your application, a predefined model can be a good choice.

    \table
        \row
            \o  QStringListModel
            \o  Stores a list of strings
        \row
            \o  QStandardItemModel
            \o  Stores arbitrary hierarchical items
        \row
            \o  QFileSystemModel\br
                QDirModel
            \o  Encapsulate the local file system
        \row
            \o  QSqlQueryModel
            \o  Encapsulate an SQL result set
        \row
            \o  QSqlTableModel
            \o  Encapsulates an SQL table
        \row
            \o  QSqlRelationalTableModel
            \o  Encapsulates an SQL table with foreign keys
        \row
            \o  QSortFilterProxyModel
            \o  Sorts and/or filters another model

    \endtable

    \section2 3.4 Delegates

    In all examples so far, data is presented as text or a checkbox in a cell
    and is edited as text or a checkbox. The component that provides these
    presentation and editing services is called a \e delegate. We are only just
    beginning to work with the delegate because the view uses a default
    delegate.  But imagine that we want to have a different editor.(e.g. a
    slider or a drop down list) Or imagine that we want to present data as
    graphics. Let's take a look at an example called
    \l{Star Delegate Example}{Star Delegate}, in which stars are used to show
    a rating:
    \image stardelegate.png

    The view has a method that replaces the default delegate and installs a
    custom delegate. This method is called
    \l{QAbstractItemView::}{setItemDelegate()}. A new delegate can be written
    by creating a class that inherits from QStyledItemDelegate. In order to
    write a delegate that displays stars and has no input capabilities, we only
    need to overwrite 2 methods.

    \code
     class StarDelegate : public QStyledItemDelegate
     {
         Q_OBJECT
     public:
         StarDelegate(QWidget *parent = 0); 
         void paint(QPainter *painter, const QStyleOptionViewItem &option,
                    const QModelIndex &index) const;
         QSize sizeHint(const QStyleOptionViewItem &option,
                        const QModelIndex &index) const;
     };
    \endcode

    \l{QStyledItemDelegate::}{paint()} draws stars depending on the content
    of the underlying data.  The data can be looked up with parameter
    \l{QModelIndex::data()}{index.data()}.
    \l{QAbstractItemDelegate::}{sizeHint()} specifies each star's dimensions
    so the the cell will provide enough height and width to accommodate the
    stars.

    Writing custom delegates is the right choice if you want to show your data
    with a custom graphical representation inside the grid of the view class.
    If you want to leave the grid, you can write a custom view class.

    \section2 3.5 Debugging with ModelTest

    The passive nature of models provides new challenges for programmers.
    Inconsistencies in the model can cause the application to crash. Since the
    model is hit by numerous calls from the view, it is hard to find out which
    call has crashed the application and which operation has introduced the
    problem. 

    Qt provides software called
    \l{http://labs.qt.nokia.com/page/Projects/Itemview/Modeltest}{ModelTest},
    which checks models while your programming is running. Every time the model
    is changed, ModelTest scans the model and reports errors with an assert.
    This is especially important for tree models, since their hierarchical
    nature leaves many possibilities for subtle inconsistencies.

    Unlike view classes, ModelTest uses out of range indexes to test the model.
    This means your application may crash with ModelTest even if it runs
    perfectly without it. So you also need to handle all of the indexes that
    are out of range when using ModelTest. 


    \section2 3.6 Model/View NG

    \raw HTML
    <table style="background-color:white;border:none;font: normal 13px/1.2 Verdana;">
    <tr><td align="left" valign="top" style="background-color:white;border:none;padding:5px;">
    \endraw

    \raw HTML
    <!-- wrap content table p has 0 padding and the padding for p outside of the table is 5px-->
    \endraw

    Model/View was introduced in Qt 4.0 and is a frequently used technology.
    Feedback from developers and new development trends have shown that there
    is a need to further develop the model/view technology. Therefore a
    research project originated at Nokia is looking into ways to go beyond the
    current implementation.

    One limitation of model/view is that view classes are basically all fixed
    grids. It is possible, but really hard to make a list view with icons
    placed on a curve; or cells expanding on mouse over events to show
    additional information.
    In order to achieve graphically rich view experiences, Model/View NG will
    use QGraphicsView to render elements. Nodel/View NG also aims to make
    model/view programming more intuitive. One way to achieve this is to have
    separate models for lists, tables and trees. The current model abstraction
    is complex because it is capable of representing a list, a table or a tree.

    Model/View NG is a research project. You are welcome to checkout the source
    code, monitor progress and take part in discussions at the following
    address: \l{http://labs.qt.nokia.com/page/Projects/Itemview/ItemviewsNG}

    \raw HTML
    </td><td align="right" valign="top">
    \endraw

    \inlineimage path.png

    \raw HTML
    </td></tr></table>
    \endraw
*/

/*!
    \page modelview-part4.html
    \contentspage {modelview-index.html}{Model/View Contents}
    \previouspage {modelview-part3.html}{Intermediate Topics}
    \title Model/View Chapter 4 - Good Sources of Additional Information

    \section1 4. Good Sources of Additional Information

    \section2 4.1 Books

    Model/View programming is covered quite extensively in the documentation of
    Qt but also in several good books.

    \list 1
       \o \bold{C++ GUI Programming with Qt 4} / Jasmin Blanchette, Mark Summerfield,
          \e{Prentice Hall, 2nd edition}, ISBN 0-13-235416-0. Also available in
          German: C++ GUI Programmierung mit Qt 4: Die offizielle Einführung,
          \e{Addison-Wesley}, ISBN 3-827327-29-6
       \o \bold{The Book of Qt4, The Art of Building Qt Applications} / Daniel Molkentin,
          \e{Open Source Press}, ISBN 1-59327-147-6.
          Translated from \bold{Qt 4, Einführung in die Applikationsentwicklung},
          \e{Open Source Press}, ISBN 3-937514-12-0.
       \o \bold{Foundations of Qt Development} / Johan Thelin, \e{Apress}, ISBN 1-59059-831-8.
    \endlist

    More information about these books is available on the
    \l{Books about Qt Programming}{Qt Web site}.

    The following list provides an overview of example programs contained in the
    books above. Some of them make very good templates for developing similar
    applications.

    \table
        \header
            \o  example name
            \o  view class used
            \o  model used
            \o  aspects touched
            \o
        \row
            \o  Team Leaders
            \o  QListview
            \o  QStringListModel
            \o
            \o  Book 1, Chapter 10, Figure 10.6
        \row
            \o  Directory Viewer
            \o  QTreeView
            \o  QDirModel
            \o
            \o  Book 1, Chapter 10, Figure 10.7
        \row
            \o  Color Names
            \o  QListView
            \o  QSortFilterProxyModel
                applied to QStringListModel
            \o
            \o  Book 1, Chapter 10, Figure 10.8
        \row
            \o  Currencies
            \o  QTableView
            \o  custom model based on
                QAbstractTableModel
            \o  read only
            \o  Book 1, Chapter 10, Figure 10.10
        \row
            \o  Cities
            \o  QTableView
            \o  custom model based on
                QAbstractTableModel
            \o  read / write
            \o  Book 1, Chapter 10, Figure 10.12
        \row
            \o  Boolean Parser
            \o  QTreeView
            \o  custom model based on
                QAbstractItemModel
            \o  read only
            \o  Book 1, Chapter 10, Figure 10.14
        \row
            \o  Track Editor
            \o  {2, 1} QTableWidget
            \o  custom delegate providing a custom editor
            \o  Book 1, Chapter 10, Figure 10.15

        \row
            \o  Four directory views
            \o  QListView
                QTableView
                QTreeView
            \o  QDirModel
            \o  demonstrates the use of multiple views
            \o  Book2, Chapter 8.2
        \row
            \o  Address Book
            \o  QListView
                QTableView
                QTreeView
            \o  custom model based on
                QAbstractTableModel
            \o  read / write
            \o  Book2, Chapter 8.4
        \row
            \o  Address Book with sorting
            \o
            \o  QProxyModel
            \o  introducing sort and filter capabilities
            \o  Book2, Chapter 8.5
        \row
            \o  Address Book
                with checkboxes
            \o
            \o
            \o  introducing checkboxes in model/view
            \o  Book2, Chapter 8.6
        \row
            \o  Address Book with transposed grid
            \o
            \o  custom proxy Model based on QAbstractProxyModel
            \o  introducing a custom model
            \o  Book2, Chapter 8.7
        \row
            \o  Address Book with drag and drop
            \o
            \o
            \o  introducing drag and drop support
            \o  Book2, Chapter 8.8
        \row
            \o  Address Book with custom editor
            \o
            \o
            \o  introducing custom delegates
            \o  Book2, Chapter 8.9
        \row
            \o  Views
            \o  QListView
                QTableView
                QTreeView
            \o  QStandardItemModel
            \o  read only
            \o  Book 3, Chapter 5, figure 5-3
        \row
            \o  Bardelegate
            \o  QTableView
            \o
            \o  custom delegate for presentation based on QAbstractItemDelegate
            \o  Book 3, Chapter 5, figure 5-5
        \row
            \o  Editdelegate
            \o  QTableView
            \o
            \o  custom delegate for editing based on QAbstractItemDelegate
            \o  Book 3, Chapter 5, figure 5-6
        \row
            \o  Singleitemview
            \o  custom view based on QAbstractItemView
            \o
            \o  custom view
            \o  Book 3,
                Chapter 5,
                figure 5-7
        \row
            \o  listmodel
            \o  QTableView
            \o  custom Model based on QAbstractTableModel
            \o  read only
            \o  Book 3, Chapter 5, Figure 5-8
        \row
            \o  treemodel
            \o  QTreeView
            \o  custom Model based on QAbstractItemModel
            \o  read only
            \o  Book 3, Chapter 5, Figure 5-10
        \row
            \o  edit integers
            \o  QListView
            \o  custom Model based on QAbstractListModel
            \o  read / write
            \o  Book 3, Chapter 5, Listing 5-37, Figure 5-11
        \row
            \o  sorting
            \o  QTableView
            \o  QSortFilterProxyModel applied to QStringListModel
            \o  demonstrates sorting
            \o  Book 3, Chapter 5, Figure 5-12
    \endtable


    \section2 4.2 Qt Documentation

    Qt 4.7 comes with 17 examples and 2 Demonstrations for model/view.
    The examples can be found here: \l{Item Views Examples}
    \table
        \header
            \o  Example name
            \o  View class used
            \o  Model used
            \o  Aspects touched
        \row
            \o  Address Book
            \o  QTableView
            \o  QAbstractTableModel
                QSortFilterProxyModel
            \o  usage of QSortFilterProxyModel to generate different
                subsets from one data pool
        \row
            \o  Basic Sort/Filter Model
            \o  QTreeView
            \o  QStandardItemModel
                QSortFilterProxyModel
            \o
        \row
            \o  Chart
            \o  custom view
            \o  QStandardItemModel
            \o  designing custom views that cooperate with selection models 
        \row
            \o  Color Editor Factory
            \o  {2, 1}  QTableWidget
            \o  enhancing the standard delegate with a new custom editor to choose colours
        \row
            \o  Combo Widget Mapper
            \o  QDataWidgetMapper to map QLineEdit, QTextEdit and QComboBox
            \o  QStandardItemModel
            \o  shows how a QComboBox can serve as a view class
        \row
            \o  Custom Sort/Filter Model
            \o  QTreeView
            \o  QStandardItemModel
                QSortFilterProxyModel
            \o  subclass QSortFilterProxyModel for advanced sorting and filtering
        \row
            \o  Dir View
            \o  QTreeView
            \o  QDirModel
            \o  very small example to demonstrate how to assign a model to a view
        \row
            \o  Editable Tree Model
            \o  QTreeView
            \o  custom tree model
            \o  comprehensive example for working with trees, demonstrates
                editing cells and tree structure with an underlying custom
                model
        \row
            \o  Fetch More
            \o  QListView
            \o  custom list model
            \o  dynamically changing model
        \row
            \o  Frozen Column
            \o  QTableView
            \o  QStandardItemModel
            \o
        \row
            \o  Pixelator
            \o  QTableView
            \o  custom table model
            \o  implementation of a custom delegate
        \row
            \o  Puzzle
            \o  QListView
            \o  custom list model
            \o  model/view with drag and drop 
        \row
            \o  Simple DOM Model
            \o  QTreeView
            \o  custom tree model
            \o  read only example for a custom tree model
        \row
            \o  Simple Tree Model
            \o  QTreeView
            \o  custom tree model
            \o  read only example for a custom tree model
        \row
            \o  Simple Widget Mapper
            \o  QDataWidgetMapper to map QLineEdit, QTextEdit and QSpinBox
            \o  QStandardItemModel
            \o  basic QDataWidgetMapper usage
        \row
            \o  Spin Box Delegate
            \o  QTableView
            \o  QStandardItemModel
            \o  custom delegate that uses a spin box as a cell editor
        \row
            \o  Star Delegate
            \o  {2, 1}  QTableWidget
            \o  comprehensive custom delegate example. 
    \endtable

    \l{Qt Demonstrations}{Demonstrations} are similar to examples except
    that no walkthrough is provided for the code. Demonstrations are also
    sometimes more feature rich.

    \list
       \o   The \bold Interview demonstration shows the same model and
            selection being shared between three different views.
       \o   Demonstration \bold Spreadsheet demonstrates the use of a
            table view as a spreadsheet, using custom delegates to render
            each item according to the type of data it contains.
    \endlist

    A \l{Model/View Programming}{reference document} for model/view technology
    is also available.
*/