QTextEdit does not get drawn correctly after adjusting scrollbar on Mac OS X

On Qt for Mac, If many lines are added quickly using the append slot QTextEdit often misrenders the text after a resizing of the window... it shows multiple instances of the same lines, so that the display looks wrong and is hard to read.

This can be seen with the following example :

#include <QtGui>

//class MyTextEdit : public QPlainTextEdit
class MyTextEdit : public QTextEdit
{
Q_OBJECT

public:
MyTextEdit();

private slots:
void AddSomeText();
};

MyTextEdit :: MyTextEdit()
{
setReadOnly(true);
QTimer::singleShot(200, this, SLOT(AddSomeText()));
}

void MyTextEdit :: AddSomeText()
{
static int count = 0;
for (int i=0; i<6; i++)

{ // appendPlainText(QString("This is Plain Text loop %2 with a string containing some text %1").arg(count++).arg(i)); append(QString("This is QTextEdit loop %2 with a string containing some text %1").arg(count++).arg(i)); }

QScrollBar * sb = verticalScrollBar();
sb->setValue(sb->maximum());

QTimer::singleShot(2000, this, SLOT(AddSomeText()));
}

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

QWidget w;
w.setMinimumWidth(640);
QBoxLayout * vbl = new QBoxLayout(QBoxLayout::TopToBottom, &w);
vbl->setMargin(5);
vbl->setSpacing(5);

MyTextEdit * mpte = new MyTextEdit;
vbl->addWidget(mpte);

w.show();

return app.exec();
}
#include "main.moc"