Hmm, I think I celebrated too early. Everything I did above worked great; so long as I kept the DP port connected monitor set to the left in the display orientation of KDE. The moment I switched the DP monitor to the right of the laptop; chaos ensued.
I started another thread on this phenomenon @ Swapped position of FW16 & dGPU DP displays in KDE (X11), now steam games launch "confused", but thought I’d post here after I discovered a second scenario that strengthened my growing sense that using the dGPU port to drive a monitor also requires it to be set to the left-most monitor.
The short version (will keep the details about what a “confused game” and the “invisible line” means in the other thread):
- DP monitor direct connected to dGPU, orientation set so that monitor is on the left of the laptop, games play beautifully. settings as previously posted
- Moved laptop from table to desk, swapped orientation of monitors physically and in kde settings so the DP (still connected to dGPU) is on the right. launched game and it opens on the wrong monitor and introduces the “invisible line”. Reversing my /usr/share/sddm/scripts/Xsetup did not correct the behavior… but reversing the left/right monitors in KDE display orientation did correct the behaviour… direct connected dGPU monitor set to the left in KDE
- Moved the DP monitor to the side iGPU DP connection. Set KDE orientation so DP monitor is on the right (matching physical orientation). Removed
/usr/share/sddm/scripts/Xsetupsettings (not needed with SDDM using the iGPU). Rebooted and games behave properly; loading on the DP monitor (primary display in KDE) and no “invisible line”… and stayed true even if I swapped orientations between left and right inside KDE settings.
All scenarios above suggest:
- When an external monitor is direct connected to the dGPU, set it’s orientation as the left monitor or problems will occur in games
- When an external monitor is connected to the iGPU, set whatever orientation you want, there will be no problems.
------- Update -------
I think it is also important to note that this is while booted into a KDE X11 session. If I log out and launch KDE wayland the “windowed” game behaves properly, but a fullscreen game crashed xwayland… and so I stick to x11 where my game at least all launch.
------- Update 2 -------
I think I figured out another important detail… some steam games have a native linux version whereas many require PROTON to allow windows games to run on Linux. The two games focused on in my writings were not Linux native games, so PROTON / VULKAN / etc is involved. Launched a 3rd windowed game that has a Linux native version, and it launched/behaved properly.