QPlainTextEdit:text lines are not drawn correcty on Mac OS X after adjusting scrollbar

On Qt for Mac, If many lines are added quickly using the appendPlainText slot QPlainTextEdit often misrenders the text after a resizing of the window... it doesn't render some or all of some of the 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"