When I switch the main Screen on multiple screen, the main screen has to be on the left side, or the change won't apply. -> main screen must alwys be left.
I can confirm this bug. Please find my report below. I have an external monitor connected to a laptop. From the user’s perspective, the external monitor is on the RHS of the laptop. Using the XFCE4 “Settings-Display” app I configure as follows: • “Use this display” is selected for both monitors. • “Primary display” is selected for the external monitor. • “Mirror displays” is clear for both monitors. • Using the apps schematic, the external monitor is positioned to the RHS of the laptop, to reflect the actual physical configuration. Despite the above configuration, the Laptop display is set as the primary display; it alone shows the taskbar. If the setttings schematic is changed by moving the laptop display to the RHS of the external monitor then the external monitor correctly becomes the “primary display”. However, to move a window from the primary monitor to the laptop monitor I then have to drag it to the right; this is very counter-intuitive as the laptop is actually on the left. This is the only method I have found that successfully sets the external monitor as the primary display. I have no intention of ever switching back to KDE, but just to point out that this cannot be a hardware issue I can report that the monitors can be configured correctly in that environment; the problem is only in XFCE. XRANDR reports my configuration as follows: • Outputs are ◦ Laptop LVDS-1 1280x800 ◦ External Monitor DVI-D-1 1280x1024 primary • The commands xrandr --output LVDS-1 –primary xrandr --output DVI-D-1 –primary have no effect. However, xrandr -q reports the change in primary monitor (but no change occurs from the user point of view). I am running XFCE 4.12
Xfce 4.12 doesn't support the "primary monitor" setting. For more on what we have fixed for the upcoming 4.14 please continue reading here: https://simon.shimmerproject.org/2018/11/12/adventures-in-primary-display-land/ For 4.12 this is - unfortunately - a Won't Fix.