Bad Performance of QPainter::drawText on Linux

I have noticed that QPainter::drawText is horribly slow on Linux when using it with a scaled window mapping. Is there anything I can do about this? I already checked whether disabling anti-aliasing or enabled the raster-renderer makes a difference, but it doesn't. People on StackOverflow suggested to post it here since it seems to be a Qt bug.

Example: When using a viewport size of (450px, 200px), a window size of factor 100 (45000, 20000) and thus font sizes scaled up by factor 100 as well (1400pt), rendering 30 times the text "hello" takes about 4 seconds on Linux - both on OpenSuse and Ubuntu.

The same sample renders in a snap on Windows and Mac.

Just for clarification: although the font size is scaled up, the text appears in "normal" size on screen due to the described window<->viewport mapping.

Here is the simple sample code I am using:

void Widget::paintEvent(QPaintEvent *event)
{
const int scaleFactor = 100;

QPainter painter(this);

// Setup font
QFont font;
font.setPointSize(14*scaleFactor);
painter.setFont(font);

// Setup mapping
painter.setWindow(0, 0, width() * scaleFactor, height() * scaleFactor);

// Render the text
for (int i = 0; i < 30; i++)
painter.drawText(qrand() % (width() * scaleFactor), qrand() % (height() * scaleFactor), "Hello");
}