Multidisplay configuration randomly/unpredictably changes with each boot or return from screen-lock(screen-dim)

[Miroslav Zaťko]

Multidisplay configuration randomly/unpredictably changes with each boot or screen-unlock.

My hardware configuration is thinkpad P50 with intel/nvidia hybrid display adapters. "Internal" high-dpi 3840x2160px + "External" high-dpi 3840x2160px displays.

Multidisplay configuration which I am trying to achieve is: both monitors in 1920x1080px mode configured as extended desktop. I am mostly able to achieve it using "Displays" tool even there is some strange behavior(for example changing rotation of display when only switching resolution)

Problem: after almost each(let say 80%) boot and screen-unlock are display settings randomly/unpredictably changed and I have to do all displays setup again or even to restart lightdm. This is a bit curious as after boot, the setup is mostly misconfigured bud after restart only lightdm service it is much more often correct.
One important think is that this misconfiguration happend after login, greeter seems to be setup correct after almost each reboot or lightdm restart. Login is followed by some unwanted/unnecessary blinking and display modes switching which ends as misconfiguration mostly.

Some examples:
- both or one of monitor is set to native 3840x2160px resolution
- mirroring is set instead of extended desktop
- if kept in last correct 1920x1080px resolution then some weird panning is applied for one or both displays

- the same behavior occurs using any nvidia-XXX driver available in ubuntu or launchpad repositories.
- nouveau driver seems to not support any multidisplay configuration

Description: Ubuntu 15.10
Release: 15.10

ProblemType: Bug
DistroRelease: Ubuntu 15.10
Package: lightdm 1.16.7-0ubuntu1
ProcVersionSignature: Ubuntu 4.2.0-34.39-generic 4.2.8-ckt4
Uname: Linux 4.2.0-34-generic x86_64
NonfreeKernelModules: nvidia_uvm nvidia_drm nvidia_modeset nvidia
ApportVersion: 2.19.1-0ubuntu5
Architecture: amd64
CurrentDesktop: Unity
Date: Sat Mar 26 16:22:26 2016
InstallationDate: Installed on 2016-03-25 (0 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
SourcePackage: lightdm
UpgradeStatus: No upgrade log present (probably fresh install)