mainwindow.cpp Example File
xmlpatterns/schema/mainwindow.cpp

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 #include <QtGui>
 #include <QtXmlPatterns>

 #include "mainwindow.h"
 #include "xmlsyntaxhighlighter.h"

 class MessageHandler : public QAbstractMessageHandler
 {
     public:
         MessageHandler()
             : QAbstractMessageHandler(0)
         {
         }

         QString statusMessage() const
         {
             return m_description;
         }

         int line() const
         {
             return m_sourceLocation.line();
         }

         int column() const
         {
             return m_sourceLocation.column();
         }

     protected:
         virtual void handleMessage(QtMsgType type, const QString &description,
                                    const QUrl &identifier, const QSourceLocation &sourceLocation)
         {
             Q_UNUSED(type);
             Q_UNUSED(identifier);

             m_messageType = type;
             m_description = description;
             m_sourceLocation = sourceLocation;
         }

     private:
         QtMsgType m_messageType;
         QString m_description;
         QSourceLocation m_sourceLocation;
 };

 MainWindow::MainWindow()
 {
     setupUi(this);

     new XmlSyntaxHighlighter(schemaView->document());
     new XmlSyntaxHighlighter(instanceEdit->document());

     schemaSelection->addItem(tr("Contact Schema"));
     schemaSelection->addItem(tr("Recipe Schema"));
     schemaSelection->addItem(tr("Order Schema"));

     instanceSelection->addItem(tr("Valid Contact Instance"));
     instanceSelection->addItem(tr("Invalid Contact Instance"));

     connect(schemaSelection, SIGNAL(currentIndexChanged(int)), SLOT(schemaSelected(int)));
     connect(instanceSelection, SIGNAL(currentIndexChanged(int)), SLOT(instanceSelected(int)));
     connect(validateButton, SIGNAL(clicked()), SLOT(validate()));
     connect(instanceEdit, SIGNAL(textChanged()), SLOT(textChanged()));

     validationStatus->setAlignment(Qt::AlignCenter | Qt::AlignVCenter);

     schemaSelected(0);
     instanceSelected(0);
 }

 void MainWindow::schemaSelected(int index)
 {
     instanceSelection->clear();
     if (index == 0) {
         instanceSelection->addItem(tr("Valid Contact Instance"));
         instanceSelection->addItem(tr("Invalid Contact Instance"));
     } else if (index == 1) {
         instanceSelection->addItem(tr("Valid Recipe Instance"));
         instanceSelection->addItem(tr("Invalid Recipe Instance"));
     } else if (index == 2) {
         instanceSelection->addItem(tr("Valid Order Instance"));
         instanceSelection->addItem(tr("Invalid Order Instance"));
     }
     textChanged();

     QFile schemaFile(QString(":/schema_%1.xsd").arg(index));
     schemaFile.open(QIODevice::ReadOnly);
     const QString schemaText(QString::fromUtf8(schemaFile.readAll()));
     schemaView->setPlainText(schemaText);

     validate();
 }

 void MainWindow::instanceSelected(int index)
 {
     QFile instanceFile(QString(":/instance_%1.xml").arg((2*schemaSelection->currentIndex()) + index));
     instanceFile.open(QIODevice::ReadOnly);
     const QString instanceText(QString::fromUtf8(instanceFile.readAll()));
     instanceEdit->setPlainText(instanceText);

     validate();
 }

 void MainWindow::validate()
 {
     const QByteArray schemaData = schemaView->toPlainText().toUtf8();
     const QByteArray instanceData = instanceEdit->toPlainText().toUtf8();

     MessageHandler messageHandler;

     QXmlSchema schema;
     schema.setMessageHandler(&messageHandler);

     schema.load(schemaData);

     bool errorOccurred = false;
     if (!schema.isValid()) {
         errorOccurred = true;
     } else {
         QXmlSchemaValidator validator(schema);
         if (!validator.validate(instanceData))
             errorOccurred = true;
     }

     if (errorOccurred) {
         validationStatus->setText(messageHandler.statusMessage());
         moveCursor(messageHandler.line(), messageHandler.column());
     } else {
         validationStatus->setText(tr("validation successful"));
     }

     const QString styleSheet = QString("QLabel {background: %1; padding: 3px}")
                                       .arg(errorOccurred ? QColor(Qt::red).lighter(160).name() :
                                                            QColor(Qt::green).lighter(160).name());
     validationStatus->setStyleSheet(styleSheet);
 }

 void MainWindow::textChanged()
 {
     instanceEdit->setExtraSelections(QList<QTextEdit::ExtraSelection>());
 }

 void MainWindow::moveCursor(int line, int column)
 {
     instanceEdit->moveCursor(QTextCursor::Start);
     for (int i = 1; i < line; ++i)
         instanceEdit->moveCursor(QTextCursor::Down);

     for (int i = 1; i < column; ++i)
         instanceEdit->moveCursor(QTextCursor::Right);

     QList<QTextEdit::ExtraSelection> extraSelections;
     QTextEdit::ExtraSelection selection;

     const QColor lineColor = QColor(Qt::red).lighter(160);
     selection.format.setBackground(lineColor);
     selection.format.setProperty(QTextFormat::FullWidthSelection, true);
     selection.cursor = instanceEdit->textCursor();
     selection.cursor.clearSelection();
     extraSelections.append(selection);

     instanceEdit->setExtraSelections(extraSelections);

     instanceEdit->setFocus();
 }