[Qt-interest] Is QPainter::HighQualityAntialiasing render hint broken in Qt 4.6?

[liang jian]

    I seems that QPainter::HighQualityAntialiasing render hint is
broken in Qt 4.6. if I run overpainting exmaple In 4.5.3 with
QPainter::HighQualityAntialiasing render hint the image quality is far
better than that with QPainter::Antialiasing render hint. But now with
Qt 4.6, it show no difference, and the image quality is the same as
4.5.3 with QPainter::Antialiasing even if I have set
QPainter::HighQualityAntialiasing render hint. I know Qt 4.6 have
rewrote opengl paint engine, is this a side-effect or a bug?