Bottom portion of screen is black/blank with 4 monitor display

[peter royal]

I have 4 monitors in a single X display using NVidia Base Mosaic. Using Ubuntu GNOME

I have two landscape monitors stacked with a portrait on either side.

If the portrait monitors are configured such that the BOTTOM of their screens align with the BOTTOM landscape monitor, both portraits and the bottom landscape monitor will not display anything below the lower 1/2 of the screen. I can move the pointer to the lower portion of the screen, and see the pointer there, but if I try and drag a window it acts as if there's an artificial bottom. It seems that the size of the non-displayable area is the same as the distance between the top of the portrait screens and the top of the landscape screens.

(I attached a screenshot of the displays configuration. The problem is when 3 and 4 are bottom aligned)

If the portrait monitors are configured such that the TOP of their screens align with the TOP landscape monitor, everything works as expected.

I do not believe this is an explicit X server issue because if I take my Gnome monitors.xml and have lightdm use that, everything works as expected. I believe it is related to the Gnome display manager. It is as if something that is deciding what the visible display area is has some bad math with this layout.

This was all functioning properly under 14.04.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: xorg 1:7.7+7ubuntu4
ProcVersionSignature: Ubuntu 3.19.0-21.21-generic 3.19.8
Uname: Linux 3.19.0-21-generic x86_64
NonfreeKernelModules: nvidia
.proc.driver.nvidia.registry: Binary: ""
.proc.driver.nvidia.version:
 NVRM version: NVIDIA UNIX x86_64 Kernel Module 340.76 Thu Jan 22 12:11:08 PST 2015
 GCC version: gcc version 4.9.2 (Ubuntu 4.9.2-10ubuntu13)
ApportVersion: 2.17.2-0ubuntu1.1
Architecture: amd64
CurrentDesktop: GNOME
Date: Fri Jun 26 08:12:55 2015
DistUpgraded: 2015-06-25 11:27:46,831 DEBUG enabling apt cron job
DistroCodename: vivid
DistroVariant: ubuntu
DkmsStatus:
 bbswitch, 0.7, 3.13.0-39-generic, x86_64: installed
 bbswitch, 0.7, 3.16.0-41-generic, x86_64: installed
 bbswitch, 0.7, 3.19.0-21-generic, x86_64: installed
 nvidia-340, 340.76, 3.19.0-21-generic, x86_64: installed
GraphicsCard:
 NVIDIA Corporation GM107GL [Quadro K620] [10de:13bb] (rev a2) (prog-if 00 [VGA controller])
   Subsystem: NVIDIA Corporation Device [10de:1098]
 NVIDIA Corporation GM107GL [Quadro K620] [10de:13bb] (rev a2) (prog-if 00 [VGA controller])
   Subsystem: NVIDIA Corporation Device [10de:1098]
MachineType: Hewlett-Packard HP Z600 Workstation
ProcKernelCmdLine: root=UUID=fc29ed89-f722-473a-b519-7af62918be40 ro quiet splash
SourcePackage: xorg
Symptom: display
UpgradeStatus: Upgraded to vivid on 2015-06-25 (0 days ago)
dmi.bios.date: 07/09/2010
dmi.bios.vendor: Hewlett-Packard
dmi.bios.version: 786G4 v03.10
dmi.board.name: 0AE8h
dmi.board.vendor: Hewlett-Packard
dmi.board.version: C
dmi.chassis.type: 6
dmi.chassis.vendor: Hewlett-Packard
dmi.modalias: dmi:bvnHewlett-Packard:bvr786G4v03.10:bd07/09/2010:svnHewlett-Packard:pnHPZ600Workstation:pvr:rvnHewlett-Packard:rn0AE8h:rvrC:cvnHewlett-Packard:ct6:cvr:
dmi.product.name: HP Z600 Workstation
dmi.sys.vendor: Hewlett-Packard
version.compiz: compiz N/A
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.60-2
version.libgl1-mesa-dri: libgl1-mesa-dri 10.5.2-0ubuntu1
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 10.5.2-0ubuntu1
version.nvidia-graphics-drivers: nvidia-graphics-drivers N/A
version.xserver-xorg-core: xserver-xorg-core 2:1.17.1-0ubuntu3
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.9.0-1ubuntu2
version.xserver-xorg-video-ati: xserver-xorg-video-ati N/A
version.xserver-xorg-video-intel: xserver-xorg-video-intel N/A
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau N/A
xserver.bootTime: Thu Jun 25 12:36:38 2015
xserver.configfile: /etc/X11/xorg.conf
xserver.devices:
 input Power Button KEYBOARD, id 6
 input Power Button KEYBOARD, id 7
 input Microsoft Microsoft Basic Optical Mouse v2.0 MOUSE, id 8
 input Lite-On Technology Corp. HP Basic USB Keyboard KEYBOARD, id 9
 input HP WMI hotkeys KEYBOARD, id 10
xserver.errors:

xserver.logfile: /var/log/Xorg.0.log
xserver.outputs:

xserver.version: 2:1.17.1-0ubuntu3

[peter royal (peter-royal)]

I have tried the nvidia-331, 340, 346 and 352 drivers and the problem is present with all of them. I do not believe it is a driver issue.

[Daniel van Vugt (vanvugt)]

Thank you for reporting this bug to Ubuntu.
Ubuntu 15.04 (vivid) reached end-of-life on February 4, 2016.

See this document for currently supported Ubuntu releases:
https://wiki.ubuntu.com/Releases

We appreciate that this bug may be old and you might not be interested in discussing it any more. But if you are then please upgrade to the latest Ubuntu version and re-test. If you then find the bug is still present in the newer Ubuntu version, please add a comment here telling us which new version it is in and change the bug status to Confirmed.