Drawing antialiased text on Windows very slow

[Rawk]

I'm using this code:

QPainterPath path;
foreach(QString line, lines)
{
	x = xPosition(left, hAlign, width, fontMetrics.width(line));
	path.addText(x, y, stdFont, line);
	y += lineHeight;
}
QBrush brush(font.color());
QPen pen(font.color(), font.borderF(), Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin);
if (font.borderF() > 0)
	pen.setColor(font.borderColor());
setRenderHint(QPainter::Antialiasing);
setPen(pen);
setBrush(brush);
setFont(stdFont);
drawPath(path);

QPainterPath path;
foreach(QString line, lines)
{
	x = xPosition(left, hAlign, width, fontMetrics.width(line));
	path.addText(x, y, stdFont, line);
	y += lineHeight;
}
QBrush brush(font.color());
QPen pen(font.color(), font.borderF(), Qt::SolidLine, Qt::RoundCap, Qt::RoundJoin);
if (font.borderF() > 0)
	pen.setColor(font.borderColor());
setRenderHint(QPainter::Antialiasing);
setPen(pen);
setBrush(brush);
setFont(stdFont);
drawPath(path);

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The code is used in a class which inherits from QPainter. On Linux it runs quite well, but on Windows it takes way too long. If antialiasing isn't enabled the speed is OK, but the text looks pretty bad. Do you have any idea?