I've experienced this sort of bug twice today on 16.04. Attached is a screenshot (it was quite difficult to paste a screenshot into a file and save it with most text missing :) and xserver log/debug info. Sometimes moving a mouse over the area makes the text appear, sometimes not.
ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: xorg 1:7.7+13ubuntu3
ProcVersionSignature: Ubuntu 4.4.0-21.37-generic 4.4.6
Uname: Linux 4.4.0-21-generic x86_64
.tmp.unity_support_test.0:
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
BootLog: /dev/sda1: clean, 860661/30769152 files, 38107309/123073521 blocks
CompizPlugins: No value set for `/apps/compiz-1/general/screen0/options/active_plugins'
CompositorRunning: compiz
CompositorUnredirectDriverBlacklist: '(nouveau|Intel).*Mesa 8.0'
CompositorUnredirectFSW: true
CurrentDesktop: Unity
Date: Wed May 4 13:52:35 2016
DistUpgraded: 2016-04-23 16:11:36,997 DEBUG icon theme changed, re-reading
DistroCodename: xenial
DistroVariant: ubuntu
DkmsStatus:
virtualbox, 5.0.18, 4.2.0-35-generic, x86_64: installed
virtualbox, 5.0.18, 4.4.0-21-generic, x86_64: installed
EcryptfsInUse: Yes
ExtraDebuggingInterest: Yes
GraphicsCard:
Intel Corporation Haswell-ULT Integrated Graphics Controller [8086:0a16] (rev 0b) (prog-if 00 [VGA controller])
Subsystem: Lenovo Haswell-ULT Integrated Graphics Controller [17aa:2217]
InstallationDate: Installed on 2015-12-02 (154 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
MachineType: LENOVO 20C0S1CWAU
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.4.0-21-generic root=UUID=bbf6846f-7622-4638-8e7e-286b6badb71d ro quiet splash vt.handoff=7
SourcePackage: xorg
UpgradeStatus: Upgraded to xenial on 2016-04-23 (10 days ago)
dmi.bios.date: 01/14/2016
dmi.bios.vendor: LENOVO
dmi.bios.version: GQET48WW (1.28 )
dmi.board.asset.tag: Not Available
dmi.board.name: 20C0S1CWAU
dmi.board.vendor: LENOVO
dmi.board.version: 0B98417 PRO
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvrGQET48WW(1.28):bd01/14/2016:svnLENOVO:pn20C0S1CWAU:pvrThinkPadS1Yoga:rvnLENOVO:rn20C0S1CWAU:rvr0B98417PRO:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 20C0S1CWAU
dmi.product.version: ThinkPad S1 Yoga
dmi.sys.vendor: LENOVO
version.compiz: compiz 1:0.9.12.2+16.04.20160415-0ubuntu1
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.67-1
version.libgl1-mesa-dri: libgl1-mesa-dri 11.2.0-1ubuntu2
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 11.2.0-1ubuntu2
version.xserver-xorg-core: xserver-xorg-core 2:1.18.3-1ubuntu2
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.10.1-1ubuntu2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.7.0-1
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917+git20160325-1ubuntu1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.12-1build2
xserver.bootTime: Wed May 4 11:51:56 2016
xserver.configfile: default
xserver.errors:
Wacom ISDv4 EC Pen stylus: Invalid type 'cursor' for this device.
Wacom ISDv4 EC Pen stylus: Invalid type 'touch' for this device.
Wacom ISDv4 EC Pen stylus: Invalid type 'pad' for this device.
xserver.logfile: /var/log/Xorg.0.log
xserver.outputs:
product id 1079
vendor LGD
xserver.version: 2:1.18.3-1ubuntu2
Status changed to 'Confirmed' because the bug affects multiple users.