source: trunk/doc/src/examples/qxmlstreambookmarks.qdoc@ 357

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/*!
    \example xml/streambookmarks
    \title QXmlStream Bookmarks Example

    The QXmlStream Bookmarks example provides a reader for XML Bookmark
    Exchange Language (XBEL) files using Qt's QXmlStreamReader class
    for reading, and QXmlStreamWriter class for writing the files.

    \image xmlstreamexample-screenshot.png

    \section1 XbelWriter Class Definition

    The \c XbelWriter class is a subclass of QXmlStreamReader, which provides
    an XML parser with a streaming API. \c XbelWriter also contains a private
    instance of QTreeWidget in order to display the bookmarks according to
    hierarchies.

    \snippet examples/xml/streambookmarks/xbelwriter.h 0

    \section1 XbelWriter Class Implementation

    The \c XbelWriter constructor accepts a \a treeWidget to initialize within
    its definition. We enable \l{QXmlStreamWriter}'s auto-formatting property
    to ensure line-breaks and indentations are added automatically to empty
    sections between elements, increasing readability as the data is split into
    several lines.

    \snippet examples/xml/streambookmarks/xbelwriter.cpp 0

    The \c writeFile() function accepts a QIODevice object and sets it using
    \c setDevice(). This function then writes the document type
    definition(DTD), the start element, the version, and \c{treeWidget}'s
    top-level items.

    \snippet examples/xml/streambookmarks/xbelwriter.cpp 1

    The \c writeItem() function accepts a QTreeWidget object and writes it
    to the stream, depending on its \c tagName, which can either be a "folder",
    "bookmark", or "separator".

    \snippet examples/xml/streambookmarks/xbelwriter.cpp 2

    \section1 XbelReader Class Definition

    The \c XbelReader class is a subclass of QXmlStreamReader, the pendent
    class for QXmlStreamWriter. \c XbelReader contains a private instance
    of QTreeWidget to group bookmarks according to their hierarchies.

    \snippet examples/xml/streambookmarks/xbelreader.h 0

    \section1 XbelReader Class Implementation

    The \c XbelReader constructor accepts a QTreeWidget to initialize the
    \c treeWidget within its definition. A QStyle object is used to set
    \c{treeWidget}'s style property. The \c folderIcon is set to QIcon::Normal
    mode where the pixmap is only displayed when the user is not interacting
    with the icon. The QStyle::SP_DirClosedIcon, QStyle::SP_DirOpenIcon, and
    QStyle::SP_FileIcon correspond to standard pixmaps that follow the style
    of your GUI.

    \snippet examples/xml/streambookmarks/xbelreader.cpp 0

    The \c read() function accepts a QIODevice and sets it using
    \l{QXmlStreamReader::setDevice()}{setDevice()}. The actual process
    of reading only takes place if the file is a valid XBEL 1.0 file. 
    Note that the XML input needs to be well-formed to be accepted by 
    QXmlStreamReader. Otherwise, the \l{QXmlStreamReader::raiseError()}
    {raiseError()} function is used to display an error message.

    \snippet examples/xml/streambookmarks/xbelreader.cpp 1

    The \c readUnknownElement() function reads an unknown element. The
    Q_ASSERT() macro is used to provide a pre-condition for the function.

    \snippet examples/xml/streambookmarks/xbelreader.cpp 2

    The \c readXBEL() function reads the name of a startElement and calls
    the appropriate function to read it, depending on whether if its a
    "folder", "bookmark" or "separator". Otherwise, it calls
    \c readUnknownElement().

    \snippet examples/xml/streambookmarks/xbelreader.cpp 3

    The \c readTitle() function reads the bookmark's title.

    \snippet examples/xml/streambookmarks/xbelreader.cpp 4

    The \c readSeparator() function creates a separator and sets its flags.
    The text is set to 30 "0xB7", the HEX equivalent for period, and then
    read using \c readElementText().

    \snippet examples/xml/streambookmarks/xbelreader.cpp 5

    \section1 MainWindow Class Definition

    The \c MainWindow class is a subclass of QMainWindow, with a
    \c File menu and a \c Help menu.

    \snippet examples/xml/streambookmarks/mainwindow.h 0

    \section1 MainWindow Class Implementation

    The \c MainWindow constructor instantiates the QTreeWidget object, \c
    treeWidget and sets its header with a QStringList object, \c labels.
    The constructor also invokes \c createActions() and \c createMenus()
    to set up the menus and their corresponding actions. The \c statusBar()
    is used to display the message "Ready" and the window's size is fixed
    to 480x320 pixels.

    \snippet examples/xml/streambookmarks/mainwindow.cpp 0

    The \c open() function enables the user to open an XBEL file using
    QFileDialog::getOpenFileName(). A warning message is displayed along
    with the \c fileName and \c errorString if the file cannot be read or
    if there is a parse error.

    \snippet examples/xml/streambookmarks/mainwindow.cpp 1

    The \c saveAs() function displays a QFileDialog, prompting the user for
    a \c fileName using QFileDialog::getSaveFileName(). Similar to the
    \c open() function, this function also displays a warning message if
    the file cannot be written to.

    \snippet examples/xml/streambookmarks/mainwindow.cpp 2

    The \c about() function displays a QMessageBox with a brief description
    of the example.

    \snippet examples/xml/streambookmarks/mainwindow.cpp 3

    In order to implement the \c open(), \c saveAs(), \c exit(), \c about()
    and \c aboutQt() functions, we connect them to QAction objects and
    add them to the \c fileMenu and \c helpMenu. The connections are as shown
    below:

    \snippet examples/xml/streambookmarks/mainwindow.cpp 4

    The \c createMenus() function creates the \c fileMenu and \c helpMenu
    and adds the QAction objects to them in order to create the menu shown
    in the screenshot below:

    \table
    \row
         \o \inlineimage xmlstreamexample-filemenu.png
         \o \inlineimage xmlstreamexample-helpmenu.png
    \endtable

    \snippet examples/xml/streambookmarks/mainwindow.cpp 5

    \section1 \c{main()} Function

    The \c main() function instantiates \c MainWindow and invokes the \c show()
    function.

    \snippet examples/xml/streambookmarks/main.cpp 0

    See the \l{http://pyxml.sourceforge.net/topics/xbel/}
    {XML Bookmark Exchange Language Resource Page} for more information
    about XBEL files.
*/