[REG]: Incorrect polygon rendering in 4.8.5

With the attached pyqt4/5 script, (also here) the rendering in 4.8.5 and 5.1.1 are incorrect.

Result on Debian Stable (qt4: 4.8.2, pyqt4: 4.9.3) (the good one):

on Arch Linux (qt4: 4.8.5 with patch for QTBUG-31579 included, pyqt4: 4.10.3)

on Arch Linux (qt5: 5.1.1, pyqt5: 5.0.1):

Noticing the incorrect rendering in the first one of qt4.8.5 and all of the qt5.1.1 ones.

This regression causes a issue in qtcurve theme (both qt4 and qt5 version) when drawing the v-shape arrow.