Created attachment 7688 XFCE won't start properly with nvidia's composition pipeline XFCE 4.12 stuck after inserting password at GDM. This happens after enabling composition pipeline or full composition pipeline and saving it to xorg. It's like XFCE is working but not properly, because it loads perfectly when I press Ctrl+alt +f2 then Ctrl+Alt+F7. Also documented(390.25 nvidia driver) at https://forum.manjaro.org/t/nvidia-390-25-xfce-login-problem-workaround/42070 Xubuntu 18.04 nvidia 390.48 proprietary driver XFCE 4.12 Ryzen 1700 NVIDIA 1060 GTX 6gb
Found a solution I did manage to get things sorted out regarding xorg with CompositionPipeline enabled on boot by deleting the secondary display position values in the displays.xml file for xfce in /home/XXXXX/.config/xfce4/xfconf/xfce-perchannel-xml/displays.xml (deleting that file also works).
It looks like a driver issue, perhaps something related to xfwm4 or xfce4-session, but definitively not xfdesktop. Since you fixed the issue by simply adjusting tweaking an existing configuration file, I'm going to close this bug, reopen if it still affects you somehow.