Comment # 7 on bug 1192148 from Robert Simai

(In reply to Stefan Hundhammer from comment #3)

> The problem may be that Qt made a wrong decision what exactly is your
> primary screen. Maybe that can even be configured somewhere (in KDE? With
> xrandr?), but if yes, I don't know where.

Many thanks for your explanations, this was helpful and I found the setting:
"kcmshell5 kcm_kscreen" allows to set one of the devices to "primary" which
works around this problem as then its geometry is used. I have no idea where
this is stored.

But: the modules always comes up on the same screen as the Control Center and
this is what they should use. The downside pinning the geometry to the
landscape mode display is, now the modules have "wrong" geometry when started
from the portrait mode display, geometry then is 1344x756 on 1080x1920.

The underlying issue appears to be that Qt can not deal with multiple displays
at different geometries and expects them to be all the same. Not sure if you
can fix that but thanks for looking into it, and good luck!