Corrupted HDMI output with Unity (works with, eg, Gnome shell)

The HDMI output to an external screen or projector
is corrupted, the GUI is not responsive and no further configuration can be done.

By corrupted I mean that:
* the screen is blinking from black to some colors and back
* the screen is formed of stripes that, somehow, resemble the desktop, but are misaligned and screwed up.

The system/screen status cannot be restored by disconnecting the HDMI cable,
but it seems to be not a kernel problem as I can easily restart lightdm
from a terminal (ctrl+alt+f1) to login again.

I tried with and w/o the intel drivers for both the standard kernel and the 4.0.2.
Nothing changes, the problem persists.

HDMI output works perfectly with Gnome Shell, hence I think that this is a unity/compiz bug.

The problem was not present in July.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: unity 7.3.2+15.04.20150420-0ubuntu1
ProcVersionSignature: Ubuntu 3.19.0-30.33-generic 3.19.8-ckt6
Uname: Linux 3.19.0-30-generic x86_64
.tmp.unity.support.test.0:

ApportVersion: 2.17.2-0ubuntu1.5
Architecture: amd64
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: Mon Oct 5 14:34:49 2015
DistUpgraded: Fresh install
DistroCodename: vivid
DistroVariant: ubuntu
GraphicsCard:
 Intel Corporation Haswell-ULT Integrated Graphics Controller [8086:0a16] (rev 0b) (prog-if 00 [VGA controller])
   Subsystem: Lenovo Device [17aa:3978]
InstallationDate: Installed on 2015-06-07 (120 days ago)
InstallationMedia: Ubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
MachineType: LENOVO 20268
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-3.19.0-30-generic.efi.signed root=UUID=38d98111-45b8-44b8-902a-b24bba2161fc ro quiet splash vt.handoff=7
SourcePackage: unity
UdevLog: Error: [Errno 2] No such file or directory: '/var/log/udev'
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 11/13/2014
dmi.bios.vendor: LENOVO
dmi.bios.version: 7CCN62WW
dmi.board.asset.tag: No Asset Tag
dmi.board.name: Cherry 3A Touch
dmi.board.vendor: LENOVO
dmi.board.version: 31900058WIN
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: IdeaPad U330 Touch
dmi.modalias: dmi:bvnLENOVO:bvr7CCN62WW:bd11/13/2014:svnLENOVO:pn20268:pvrIdeaPadU330Touch:rvnLENOVO:rnCherry3ATouch:rvr31900058WIN:cvnLENOVO:ct10:cvrIdeaPadU330Touch:
dmi.product.name: 20268
dmi.product.version: IdeaPad U330 Touch
dmi.sys.vendor: LENOVO
version.compiz: compiz 1:0.9.12.1+15.04.20150410.1-0ubuntu1
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.60-2
version.libgl1-mesa-dri: libgl1-mesa-dri 10.6.0-~0intel1
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 10.6.0-~0intel1
version.xserver-xorg-core: xserver-xorg-core 2:1.17.1-0ubuntu3.1
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.9.0-1ubuntu2
version.xserver-xorg-video-ati: xserver-xorg-video-ati 1:7.5.0-1ubuntu2
version.xserver-xorg-video-intel: xserver-xorg-video-intel 2:2.99.917-1~exp1ubuntu2.2
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.11-1ubuntu2build1
xserver.bootTime: Fri Oct 2 15:39:16 2015
xserver.configfile: default
xserver.errors: [dix] ELAN Touchscreen: unable to find touch point 0
xserver.logfile: /var/log/Xorg.0.log
xserver.outputs:
 product id 1331
 vendor IVO
xserver.version: 2:1.17.1-0ubuntu3.1