QFontMetrics::tightBoundingRect() broken on HighDPI displays

In my debugged case, the QFontMetrics::tightBoundingRect() returned 53 pixels width but QFontMetrics::boundingRect() only returned 17.

The value should normally be similar. I use it to scale down text on widgets so that the width  of a string fits (height would be easy with pixelSize instead of pointSize but width is not).

Obviously that did not work. On normal displays, it works fine.