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/****************************************************************************
**
** 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.
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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. Since the
XBEL reader is only concerned with reading XML elements, it makes
extensive use of the \l{QXmlStreamReader::readNextStartElement()}
convenience function.
\snippet examples/xml/streambookmarks/xbelreader.cpp 1
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
\l{QXmlStreamReader::skipCurrentElement()}. The Q_ASSERT() macro is used
to provide a pre-condition for the function.
\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.
*/
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