Qt5 still ignores fontconfig on some Linux desktops

Hello, this is a continuation of https://bugreports.qt.io/browse/QTBUG-29582 .

I run Cinnamon and MATE on openSUSE 13.2. I've tried everything to make QT5 apps obey the font settings, above all the DPI setting. QT5 apps are almost unreadable on my high resolution screen under Cinnamon. QT5 apps do obey the Gnome font settings when launched under Gnome Shell, but they look totally different under Cinnamon. I tried the following environment variables:

export DESKTOP_SESSION="gnome"
export XDG_CURRENT_DESKTOP="gnome"
QT_STYLE_OVERRIDE=gtk

But the fonts are still not at the right DPI. I'm attaching a screenshot of the issue.

A secondary and less important issue is that the color of the QT apps in Cinnamon and Mate is also wrong.

Could support please be added to QT5 so that QT5 apps obey the Cinnamon and Mate GTK settings?

Thanks a lot!