How to use QDomDocument to change the svg attribute?



  • A little svg file:

    <?xml version="1.0" standalone="no"?>
    <!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" 
    "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
    
    <svg width="100%" height="100%" version="1.1"
    xmlns="http://www.w3.org/2000/svg">
    
    <text id="HW" x="50" y="50" fill="blue" stroke="none" font-family="Microsoft YaHei" font-size="16">10</text>
    
    </svg>
    

    Now, I want to show the svg on a QSvgWidget, and change the text to "60", and repaint the QSvgWidget to show the text "60", but I failed.

    #ifndef SVG_WIDGET_H
    #define SVG_WIDGET_H
    
    #include <QWidget>
    #include <QtSvg>
    #include <QVBoxLayout>
    #include <QPushButton>
    #include <QDomDocument>
    
    class SVGWidget : public QWidget
    {
        Q_OBJECT
    
    public:
        SVGWidget(QWidget* parent = 0) : QWidget(parent)
        {
            m_btn = new QPushButton("Change");
            connect(m_btn, SIGNAL(clicked(bool)), this, SLOT(change()));
    
            QFile file(":/t.svg");
            file.open(QFile::ReadOnly | QFile::Text);
            m_domDoc.setContent(&file);
            file.close();
    
            m_svgWidget = new QSvgWidget;
            m_svgWidget->load(m_domDoc.toByteArray());
    
            QVBoxLayout* vLayout = new QVBoxLayout(this);
            vLayout->addWidget(m_btn);
            vLayout->addWidget(m_svgWidget);
    
            this->setFixedSize(800, 480);
        }
    
        ~SVGWidget()
        {
        }
    
    public slots:
        void change()
        {
            // change the value, I used two ways to try it, but both failed.
            QDomNodeList domNodeList1 = m_domDoc.elementsByTagName("text");
    
            // way 1
            QDomText domText = domNodeList1.at(0).toText();
            domText.setNodeValue("60");
            qDebug() << "way 1" << domText.nodeValue();
    
            // way 2
            QDomNode domNode = domNodeList1.at(0);
            domNode.setNodeValue("60");
            qDebug() << "way 2" << domNode.nodeValue();
    
            // repaint the widget
            m_svgWidget->load(m_domDoc.toByteArray());
        }
    
    private:
        QSvgWidget*   m_svgWidget;
        QPushButton*  m_btn;
        QDomDocument  m_domDoc;
    };
    
    #endif // SVG_WIDGET_H
    

    Can someone give me some advice?


  • Qt Champions 2017

    Hi
    text tag is inside svg tag and the 10 text is actually inside a text element.

     void change() {
        QDomElement root = m_domDoc.firstChildElement();
        qDebug() << "root=" << root.tagName();
        QDomNodeList text = root.elementsByTagName("text");
        if (text.size() && text.at(0).isElement() ) {
          QDomElement elem =  text.at(0).toElement();
          qDebug() << "text value " <<  elem.nodeValue();
          qDebug() << " text child" <<  elem.childNodes().at(0).nodeValue() << "type " << elem.childNodes().at(0).nodeName() ;
    
          elem.childNodes().at(0).setNodeValue("60"); // change it
        }
    

    output
    root= "svg"
    text value ""
    text child "10" type "#text"


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