[REG 5.5->5.6] Rotated text drawn badly on Windows high resolution screen (DPR>1, native engine only)

Rotated text is drawn very badly or not at all on a Windows high-resolution screen. When QPainter returns 1 from QPaintDevice::devicePixelRatioF(), the text looks fine. When QPainter returns 3 (which is the case on our high-res laptop) from PaintDevice::devicePixelRatioF(), the text looks bad or fails to show at all. The same example app built for Macintosh looks good on a Retina monitor.

The attached zip file reproduces the problem. It makes a QMainWindow and draws text with zero rotation, +-45 degree rotation and +-90 degree rotation. It also uses qDebug() to print the devicePixelRatio to the console. The results are shown in the attached screen shots.

The Freetype font engine does not have the issue.