Hi all,

I have a big problem and I am googling now for days (better: weeks) to find a solution, but don't. I hope someone here can help me.

I have bought a nice HiDPI monitor which requires two DVI cables to cope with the necessary bandwith. It is connected to an Nvidia graphics card. The display is logically divided into two parts side-by-side, and this appears respectively in the display configuration. A deeper check reveals that the server creates a single framebuffer, and the pseudo displays are simply showing subareas of this framebuffer. Nevertheless, KDE thinks that these are two separate displays, with the result that the task bar covers only half of the screen, "full screen" windows also, and there are additional side effects regarding dialog/menu placements and scrolling lags. The login screen has similar effects, it shows two screens. I tried to find an option of xrandr to treat this configuration as a single display and to report this (somehow) to KDE, but I didn't find a way.

Later on, I discovered that there is a somewhat older protocol, xinerama, that could solve the problem. When I turn it on, the login screen is fine, but after login, KDE either crashes or hangs at 100% of the progress bar, depending on the KDE version (there was a bug in 5.2 which caused the crash, and which is now resolved; I also tried 5.6.x version from the Kubuntu backport PPA). In the latter case, some messages from kscreen appear in syslog, saying that it misses xrandr. I would file a bug if I knew how to collect the necessary information, but I am not a Linux expert.

Is there any way to solve my problem? Is there anything that I can try? I do not believe that I am the only one who ran into this problem. Someone who is using a video wall will likely have the same problem. I would unwillingly switch to Cinnamon, which does not show such effects, as I use KDE on other machines with delight.

Regards
K.