Comment 11 for bug 850885

I have the same problem here. As additional hint: During my user session, my monitors are layouted correctly (Laptop monitor right, external left, as configured in Unity Control Center), but lightdm doesn't respect that (as ~/.config/monitors.xml isn't read by lightdm I suppose), so during login the external monitor is on the right.

The display resolutions are the same during login and user session.

This seems to lead to the problem that the display buffer needs to change because the monitors are going to be switched. Could it "solve" (optically) the problem if lightdm would just accept the multi monitor setting of the user?

This seems to need another setting in Unity Control Center/Display like "Use this settings for login screen" (needs to be "unlocked" like in user settings too).