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+/****************************************************************************
+**
+** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
+** All rights reserved.
+** Contact: Nokia Corporation (qt-info@nokia.com)
+**
+** This file is part of the documentation of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:FDL$
+** 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 Technology Preview License Agreement accompanying
+** this package.
+**
+** GNU Free Documentation License
+** Alternatively, this file may be used under the terms of the GNU Free
+** Documentation License version 1.3 as published by the Free Software
+** Foundation and appearing in the file included in the packaging of this
+** file.
+**
+** If you have questions regarding the use of this file, please contact
+** Nokia at qt-info@nokia.com.
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+/*!
+    \example itemviews/customsortfiltermodel
+    \title Custom Sort/Filter Model Example
+
+    The Custom Sort/Filter Model example illustrates how to subclass
+    QSortFilterProxyModel to perform advanced sorting and filtering.
+
+    \image customsortfiltermodel-example.png Screenshot of the Custom Sort/Filter Model Example
+
+    The QSortFilterProxyModel class provides support for sorting and
+    filtering data passed between another model and a view.
+
+    The model transforms the structure of a source model by mapping
+    the model indexes it supplies to new indexes, corresponding to
+    different locations, for views to use. This approach allows a
+    given source model to be restructured as far as views are
+    concerned, without requiring any transformations on the underlying
+    data and without duplicating the data in memory.
+
+    The Custom Sort/Filter Model example consists of two classes:
+
+    \list
+
+        \o The \c MySortFilterProxyModel class provides a custom proxy
+        model.
+
+        \o The \c Window class provides the main application window,
+        using the custom proxy model to sort and filter a standard
+        item model.
+
+    \endlist
+
+    We will first take a look at the \c MySortFilterProxyModel class
+    to see how the custom proxy model is implemented, then we will
+    take a look at the \c Window class to see how the model is
+    used. Finally we will take a quick look at the \c main() function.
+
+    \section1 MySortFilterProxyModel Class Definition
+
+    The \c MySortFilterProxyModel class inherits the
+    QSortFilterProxyModel class.
+
+    Since QAbstractProxyModel and its subclasses are derived from
+    QAbstractItemModel, much of the same advice about subclassing
+    normal models also applies to proxy models.
+
+    On the other hand, it is worth noting that many of
+    QSortFilterProxyModel's default implementations of functions are
+    written so that they call the equivalent functions in the relevant
+    source model. This simple proxying mechanism may need to be
+    overridden for source models with more complex behavior; in this
+    example we derive from the QSortFilterProxyModel class to ensure
+    that our filter can recognize a valid range of dates, and to
+    control the sorting behavior.
+
+    \snippet examples/itemviews/customsortfiltermodel/mysortfilterproxymodel.h 0
+
+    We want to be able to filter our data by specifying a given period
+    of time. For that reason, we implement the custom \c
+    setFilterMinimumDate() and \c setFilterMaximumDate() functions as
+    well as the corresponding \c filterMinimumDate() and \c
+    filterMaximumDate() functions. We reimplement
+    QSortFilterProxyModel's \l
+    {QSortFilterProxyModel::filterAcceptsRow()}{filterAcceptsRow()}
+    function to only accept rows with valid dates, and
+    QSortFilterProxyModel::lessThan() to be able to sort the senders
+    by their email adresses. Finally, we implement a \c dateInRange()
+    convenience function that we will use to determine if a date is
+    valid.
+
+    \section1 MySortFilterProxyModel Class Implementation
+
+    The \c MySortFilterProxyModel constructor is trivial, passing the
+    parent parameter on to the base class constructor:
+
+    \snippet examples/itemviews/customsortfiltermodel/mysortfilterproxymodel.cpp 0
+
+    The most interesting parts of the \c MySortFilterProxyModel
+    implementation are the reimplementations of
+    QSortFilterProxyModel's \l
+    {QSortFilterProxyModel::filterAcceptsRow()}{filterAcceptsRow()}
+    and \l {QSortFilterProxyModel::lessThan()}{lessThan()}
+    functions. Let's first take a look at our customized \c lessThan()
+    function.
+
+    \snippet examples/itemviews/customsortfiltermodel/mysortfilterproxymodel.cpp 4
+
+    We want to sort the senders by their email adresses. The \l
+    {QSortFilterProxyModel::}{lessThan()} function is used as the <
+    operator when sorting. The default implementation handles a
+    collection of types including QDateTime and String, but in order
+    to be able to sort the senders by their email adresses we must
+    first identify the adress within the given string:
+
+    \snippet examples/itemviews/customsortfiltermodel/mysortfilterproxymodel.cpp 6
+
+    We use QRegExp to define a pattern for the adresses we are looking
+    for. The QRegExp::indexIn() function attempts to find a match in
+    the given string and returns the position of the first match, or
+    -1 if there was no match. If the given string contains the
+    pattern, we use QRegExp's \l {QRegExp::cap()}{cap()} function to
+    retrieve the actual adress. The \l {QRegExp::cap()}{cap()}
+    function returns the text captured by the \e nth
+    subexpression. The entire match has index 0 and the parenthesized
+    subexpressions have indexes starting from 1 (excluding
+    non-capturing parentheses).
+
+    \snippet examples/itemviews/customsortfiltermodel/mysortfilterproxymodel.cpp 3
+
+    The \l
+    {QSortFilterProxyModel::filterAcceptsRow()}{filterAcceptsRow()}
+    function, on the other hand, is expected to return true if the
+    given row should be included in the model. In our example, a row
+    is accepted if either the subject or the sender contains the given
+    regular expression, and the date is valid.
+
+    \snippet examples/itemviews/customsortfiltermodel/mysortfilterproxymodel.cpp 7
+
+    We use our custom \c dateInRange() function to determine if a date
+    is valid.
+
+    To be able to filter our data by specifying a given period of
+    time, we also implement functions for getting and setting the
+    minimum and maximum dates:
+
+    \snippet examples/itemviews/customsortfiltermodel/mysortfilterproxymodel.cpp 1
+    \codeline
+    \snippet examples/itemviews/customsortfiltermodel/mysortfilterproxymodel.cpp 2
+
+    The get functions, \c filterMinimumDate() and \c
+    filterMaximumDate(), are trivial and implemented as inline
+    function in the header file.
+
+    This completes our custom proxy model. Let's see how we can use it
+    in an application.
+
+    \section1 Window Class Definition
+
+    The \c CustomFilter class inherits QWidget, and provides this
+    example's main application window:
+
+    \snippet examples/itemviews/customsortfiltermodel/window.h 0
+
+    We implement two private slots, \c textFilterChanged() and \c
+    dateFilterChanged(), to respond to the user changing the filter
+    pattern, case sensitivity or any of the dates. In addition, we
+    implement a public \c setSourceModel() convenience function to set
+    up the model/ view relation.
+
+    \section1 Window Class Implementation
+
+    In this example, we have chosen to create and set the source model
+    in the \c main () function (which we will come back to later). So
+    when constructing the main application window, we assume that a
+    source model already exists and start by creating an instance of
+    our custom proxy model:
+
+    \snippet examples/itemviews/customsortfiltermodel/window.cpp 0
+
+    We set the \l
+    {QSortFilterProxyModel::dynamicSortFilter}{dynamicSortFilter}
+    property that holds whether the proxy model is dynamically sorted
+    and filtered. By setting this property to true, we ensure that the
+    model is sorted and filtered whenever the contents of the source
+    model change.
+
+    The main application window shows views of both the source model
+    and the proxy model. The source view is quite simple:
+
+    \snippet examples/itemviews/customsortfiltermodel/window.cpp 1
+
+    The QTreeView class provides a default model/view implementation
+    of a tree view; our view implements a tree representation of items
+    in the application's source model.
+
+    \snippet examples/itemviews/customsortfiltermodel/window.cpp 2
+
+    The QTreeView class provides a default model/view implementation
+    of a tree view; our view implements a tree representation of items
+    in the application's source model. We add our view widget to a
+    layout that we install on a corresponding group box.
+
+    The proxy model view, on the other hand, contains several widgets
+    controlling the various aspects of transforming the source model's
+    data structure:
+
+    \snippet examples/itemviews/customsortfiltermodel/window.cpp 3
+    \snippet examples/itemviews/customsortfiltermodel/window.cpp 4
+
+    Note that whenever the user changes one of the filtering options,
+    we must explicitly reapply the filter. This is done by connecting
+    the various editors to functions that update the proxy model.
+
+    \snippet examples/itemviews/customsortfiltermodel/window.cpp 5
+
+    The sorting will be handled by the view. All we have to do is to
+    enable sorting for our proxy view by setting the
+    QTreeView::sortingEnabled property (which is false by
+    default). Then we add all the filtering widgets and the proxy view
+    to a layout that we install on a corresponding group box.
+
+    \snippet examples/itemviews/customsortfiltermodel/window.cpp 6
+
+    Finally, after putting our two group boxes into another layout
+    that we install on our main application widget, we customize the
+    application window.
+
+    As mentioned above, we create the source model in the \c main ()
+    function, calling the \c Window::setSourceModel() function to make
+    the application use it:
+
+    \snippet examples/itemviews/customsortfiltermodel/window.cpp 7
+
+    The QSortFilterProxyModel::setSourceModel() function makes the
+    proxy model process the data in the given model, in this case out
+    mail model. The \l {QAbstractItemView::}{setModel()} that the
+    view widget inherits from the QAbstractItemModel class, sets the
+    model for the view to present. Note that the latter function will
+    also create and set a new selection model.
+
+    \snippet examples/itemviews/customsortfiltermodel/window.cpp 8
+
+    The \c textFilterChanged() function is called whenever the user
+    changes the filter pattern or the case sensitivity.
+
+    We first retrieve the preferred syntax (the QRegExp::PatternSyntax
+    enum is used to interpret the meaning of the given pattern), then
+    we determine the preferred case sensitivity. Based on these
+    preferences and the current filter pattern, we set the proxy
+    model's \l {QSortFilterProxyModel::}{filterRegExp} property. The
+    \l {QSortFilterProxyModel::}{filterRegExp} property holds the
+    regular expression used to filter the contents of the source
+    model. Note that calling QSortFilterProxyModel's \l
+    {QSortFilterProxyModel::}{setFilterRegExp()} function also updates
+    the model.
+
+    \snippet examples/itemviews/customsortfiltermodel/window.cpp 9
+
+    The \c dateFilterChanged() function is called whenever the user
+    modifies the range of valid dates. We retrieve the new dates from
+    the user interface, and call the corresponding functions (provided
+    by our custom proxy model) to set the proxy model's minimum and
+    maximum dates. As we explained above, calling these functions also
+    updates the model.
+
+    \section1 The Main() Function
+
+    In this example, we have separated the application from the source
+    model by creating the model in the \c main () function. First we
+    create the application, then we create the source model:
+
+    \snippet examples/itemviews/customsortfiltermodel/main.cpp 0
+
+    The \c createMailModel() function is a convenience function
+    provided to simplify the constructor. All it does is to create and
+    return a model describing a collection of emails. The model is an
+    instance of the QStandardItemModel class, i.e., a generic model
+    for storing custom data typically used as a repository for
+    standard Qt data types. Each mail description is added to the
+    model using \c addMail(), another convenience function. See \l
+    {itemviews/customsortfiltermodel/main.cpp}{main.cpp} for details.
+*/