In the following example the text is 12 points large only in the first report generated, all later reports have small fonts. Using setDefaultFont instead works correctly.

#include <QtGui>

class MainWindow: public QMainWindow
{
Q_OBJECT
public:
MainWindow(QWidget * parent = 0)
: QMainWindow(parent), report(0)

{ m_textEdit = new QTextEdit(this); setCentralWidget(m_textEdit); QTimer *timer = new QTimer(this); connect(timer, SIGNAL(timeout()), this, SLOT(generateReport())); timer->start(1000); }

private slots:
void generateReport()

{ static int count = 0; QFont f; f.setPointSize(12); QTextDocument *oldReport = report; report = new QTextDocument(this); // report->setDefaultFont(f); // this always works QTextCursor tc(report); tc.insertText(QString("Hello Qt %1!").arg(++count)); m_textEdit->clear(); m_textEdit->setDocument(report); m_textEdit->setFont(f); // only this doesn't the second time delete oldReport; }

private:
QTextEdit * m_textEdit;
QTextDocument *report;
};

#include "main.moc"

int main(int argc, char * argv[])
{
QApplication app(argc, argv);
MainWindow mainWindow;
mainWindow.show();
return app.exec();
}