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# Outliner to show use of DOM

This example presents a small outliner program to show the basic usage of the DOM classes. The format of the outlines is the OPML format as described in http://www.opml.org/spec.

This example shows how to load a DOM tree from an XML file and how to traverse it.

Sample XML file (todos.opml):

    <?xml version="1.0" encoding="ISO-8859-1"?>
    <opml version="1.0">
        <head>
            <title>Todo List</title>
            <dateCreated>Tue, 31 Oct 2000 17:00:17 CET</dateCreated>
            <dateModified>Tue, 31 Oct 2000 17:00:17 CET</dateModified>
            <ownerName>Arthur Dent</ownerName>
            <ownerEmail>info@trolltech.com</ownerEmail>
        </head>
        <body>
            <outline text="Background">
                <outline text="This is an example todo list."/>
            </outline>
            <outline text="Books to read">
                <outline text="Science Fiction">
                    <outline text="Philip K. Dick">
                        <outline text="Do Androids Dream of Electical Sheep?"/>
                        <outline text="The Three Stigmata of Palmer Eldritch"/>
                    </outline>
                    <outline text="Robert A. Heinlein">
                        <outline text="Stranger in a Strange Land"/>
                    </outline>
                    <outline text="Isaac Asimov">
                        <outline text="Foundation and Empire"/>
                    </outline>
                </outline>
                <outline text="Qt Books (in English)">
                    <outline text="Dalheimer: Programming with Qt"/>
                    <outline text="Griffith: KDE 2/Qt Programming Bible"/>
                    <outline text="Hughes: Linux Rapid Application Development"/>
                    <outline text="Solin: Qt Programming in 24 hours"/>
                    <outline text="Ward: Qt 2 Programming for Linux and Windows 2000"/>
                </outline>
            </outline>
            <outline text="Shopping list">
                <outline text="General">
                    <outline text="Towel"/>
                    <outline text="Hair dryer"/>
                    <outline text="Underpants"/>
                </outline>
                <outline text="For Sunday">
                    <outline text="Beef"/>
                    <outline text="Rice"/>
                    <outline text="Carrots"/>
                    <outline text="Beans"/>
                    <outline text="Beer"/>
                    <outline text="Wine"/>
                    <outline text="Orange juice"/>
                </outline>
            </outline>
            <outline text="Write a letter to Ford">
            </outline>
        </body>
    </opml>

Header file (outlinetree.h):

    /****************************************************************************
    ** $Id:  qt/outlinetree.h   3.1.0-b1   edited Jun 9 2001 $
    **
    ** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
    **
    ** This file is part of an example program for Qt.  This example
    ** program may be used, distributed and modified without limitation.
    **
    *****************************************************************************/

    #ifndef OUTLINETREE_H
    #define OUTLINETREE_H

    #include <qlistview.h>
    #include <qdom.h>

    class OutlineTree : public QListView
    {
        Q_OBJECT

    public:
        OutlineTree( const QString fileName, QWidget *parent = 0, const char *name = 0 );
        ~OutlineTree();

    private:
        QDomDocument domTree;
        void getHeaderInformation( const QDomElement &header );
        void buildTree( QListViewItem *parentItem, const QDomElement &parentElement );
    };

    #endif // OUTLINETREE_H

Implementation (outlinetree.cpp):

    /****************************************************************************
    ** $Id:  qt/outlinetree.cpp   3.1.0-b1   edited Jun 9 2001 $
    **
    ** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
    **
    ** This file is part of an example program for Qt.  This example
    ** program may be used, distributed and modified without limitation.
    **
    *****************************************************************************/

    #include "outlinetree.h"
    #include <qfile.h>
    #include <qmessagebox.h>

    OutlineTree::OutlineTree( const QString fileName, QWidget *parent, const char *name )
        : QListView( parent, name )
    {
        // div. configuration of the list view
        addColumn( "Outlines" );
        setSorting( -1 );
        setRootIsDecorated( TRUE );

        // read the XML file and create DOM tree
        QFile opmlFile( fileName );
        if ( !opmlFile.open( IO_ReadOnly ) ) {
            QMessageBox::critical( 0,
                    tr( "Critical Error" ),
                    tr( "Cannot open file %1" ).arg( fileName ) );
            return;
        }
        if ( !domTree.setContent( &opmlFile ) ) {
            QMessageBox::critical( 0,
                    tr( "Critical Error" ),
                    tr( "Parsing error for file %1" ).arg( fileName ) );
            opmlFile.close();
            return;
        }
        opmlFile.close();

        // get the header information from the DOM
        QDomElement root = domTree.documentElement();
        QDomNode node;
        node = root.firstChild();
        while ( !node.isNull() ) {
            if ( node.isElement() && node.nodeName() == "head" ) {
                QDomElement header = node.toElement();
                getHeaderInformation( header );
                break;
            }
            node = node.nextSibling();
        }
        // create the tree view out of the DOM
        node = root.firstChild();
        while ( !node.isNull() ) {
            if ( node.isElement() && node.nodeName() == "body" ) {
                QDomElement body = node.toElement();
                buildTree( 0, body );
                break;
            }
            node = node.nextSibling();
        }
    }

    OutlineTree::~OutlineTree()
    {
    }

    void OutlineTree::getHeaderInformation( const QDomElement &header )
    {
        // visit all children of the header element and look if you can make
        // something with it
        QDomNode node = header.firstChild();
        while ( !node.isNull() ) {
            if ( node.isElement() ) {
                // case for the different header entries
                if ( node.nodeName() == "title" ) {
                    QDomText textChild = node.firstChild().toText();
                    if ( !textChild.isNull() ) {
                        setColumnText( 0, textChild.nodeValue() );
                    }
                }
            }
            node = node.nextSibling();
        }
    }

    void OutlineTree::buildTree( QListViewItem *parentItem, const QDomElement &parentElement )
    {
        QListViewItem *thisItem = 0;
        QDomNode node = parentElement.firstChild();
        while ( !node.isNull() ) {
            if ( node.isElement() && node.nodeName() == "outline" ) {
                // add a new list view item for the outline
                if ( parentItem == 0 )
                    thisItem = new QListViewItem( this, thisItem );
                else
                    thisItem = new QListViewItem( parentItem, thisItem );
                thisItem->setText( 0, node.toElement().attribute( "text" ) );
                // recursive build of the tree
                buildTree( thisItem, node.toElement() );
            }
            node = node.nextSibling();
        }
    }

Main (main.cpp):

    /****************************************************************************
    ** $Id:  qt/main.cpp   3.1.0-b1   edited Jun 9 2001 $
    **
    ** Copyright (C) 1992-2000 Trolltech AS.  All rights reserved.
    **
    ** This file is part of an example program for Qt.  This example
    ** program may be used, distributed and modified without limitation.
    **
    *****************************************************************************/

    #include <qapplication.h>
    #include "outlinetree.h"

    int main( int argc, char **argv )
    {
        QApplication a( argc, argv );

        OutlineTree outline( "todos.opml" );
        a.setMainWidget( &outline );
        outline.show();

        return a.exec();
    }

See also Qt XML Examples.