No window decorations and large mouse cursor after hotplugging 1× monitor into a 2× system

[Iain Lane]

My laptop has a 2× HiDPI display. In "displays" in unity-control-center, I've selected "Scale all window controls to match" as "Display with smallest controls".

1. Plug in a 1× monitor
2. The monitor is automatically initialised and the scaling factor is set to 1×
3. Open a window on the monitor
4. The mouse cursor is scaled at 2×, and the new windows have no window controls. There is a gap where they would be.

At 4, the cursor should have been 1×, and window controls should be visible.

ProblemType: Bug
DistroRelease: Ubuntu 16.10
Package: unity 7.5.0+16.10.20160606.1-0ubuntu1
ProcVersionSignature: Ubuntu 4.4.0-25.44-generic 4.4.13
Uname: Linux 4.4.0-25-generic x86_64
NonfreeKernelModules: wl
.tmp.unity_support_test.0:

ApportVersion: 2.20.2-0ubuntu1
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: Fri Jul 15 11:25:26 2016
DistUpgraded: Fresh install
DistroCodename: yakkety
DistroVariant: ubuntu
DkmsStatus:
 bcmwl, 6.30.223.248+bdcom, 4.4.0-23-generic, x86_64: installed (WARNING! Diff between built and installed module!)
 bcmwl, 6.30.223.248+bdcom, 4.4.0-25-generic, x86_64: installed (WARNING! Diff between built and installed module!)
GraphicsCard:
 Intel Corporation HD Graphics 5500 [8086:1616] (rev 09) (prog-if 00 [VGA controller])
   Subsystem: Dell HD Graphics 5500 [1028:0665]
InstallationDate: Installed on 2015-06-05 (405 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Alpha amd64 (20150605)
MachineType: Dell Inc. XPS 13 9343
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-4.4.0-25-generic.efi.signed root=/dev/mapper/ubuntu--vg-root ro quiet splash swapaccount=1 vt.handoff=7
SourcePackage: unity
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 07/14/2015
dmi.bios.vendor: Dell Inc.
dmi.bios.version: A05
dmi.board.name: 0310JH
dmi.board.vendor: Dell Inc.
dmi.board.version: A00
dmi.chassis.type: 9
dmi.chassis.vendor: Dell Inc.
dmi.modalias: dmi:bvnDellInc.:bvrA05:bd07/14/2015:svnDellInc.:pnXPS139343:pvr:rvnDellInc.:rn0310JH:rvrA00:cvnDellInc.:ct9:cvr:
dmi.product.name: XPS 13 9343
dmi.sys.vendor: Dell Inc.
version.compiz: compiz 1:0.9.12.2+16.10.20160606.2-0ubuntu1
version.ia32-libs: ia32-libs N/A
version.libdrm2: libdrm2 2.4.68-1
version.libgl1-mesa-dri: libgl1-mesa-dri 11.2.1-1ubuntu1
version.libgl1-mesa-dri-experimental: libgl1-mesa-dri-experimental N/A
version.libgl1-mesa-glx: libgl1-mesa-glx 11.2.1-1ubuntu1
version.xserver-xorg-core: xserver-xorg-core 2:1.18.3-1ubuntu6
version.xserver-xorg-input-evdev: xserver-xorg-input-evdev 1:2.10.2-1ubuntu1
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+git20160522-1ubuntu1
version.xserver-xorg-video-nouveau: xserver-xorg-video-nouveau 1:1.0.12-2
xserver.bootTime: Sat Jul 9 22:46:39 2016
xserver.configfile: default
xserver.logfile: /var/log/Xorg.0.log
xserver.outputs:
 product id 5153
 vendor SHP
xserver.version: 2:1.18.3-1ubuntu6