Just reported both:
https://bugreports.qt.io/browse/QTBUG-46700
https://bugreports.qt.io/browse/QTBUG-46778
Reverting back to 4.8.6 fixes it.
I want to use native instead of raster because:
1) when used remotely via x2go and ssh, qt apps are very fast using QT_GRAPHICSSYSTEM=native
2) with QT_GRAPHICSSYSTEM=native one is able to retain RGB subpixel hinting even over trasparent windows.
I'm using nvidia-340xx 340.76 with a geforce 9800GT and freetype2-infinality 2.4.12-2 if it matters.
Anybody can help please?
-EDIT
This does not seem to be related to an update of the xorg-server, nor to the graphic driver; i notice the same behaviour when using a remote (fast) vnc connection.
I bet it is a QT4 bug; someone could test please?