Windows flash by external screen on workspace change

[Pedro Côrte-Real]

https://gitlab.gnome.org/GNOME/gnome-shell/issues/455

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gnome-shell has the very interesting default of only doing virtual desktops on the internal screen. This works fine but has a strange visual glitch when changing virtual desktops where the contents of the internal screen flash through the external one.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: gnome-shell 3.28.1-0ubuntu2
ProcVersionSignature: Ubuntu 4.15.0-22.24-generic 4.15.17
Uname: Linux 4.15.0-22-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.1
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Thu May 31 21:06:47 2018
DisplayManager: gdm3
InstallationDate: Installed on 2018-05-31 (0 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
SourcePackage: gnome-shell
UpgradeStatus: No upgrade log present (probably fresh install)

[Daniel van Vugt (vanvugt)]

1. Please try removing all your extensions and see if the problem goes away:

b'org.gnome.shell' b'enabled-extensions' b"['<email address hidden>', '<email address hidden>', 'removeaccesibility@lomegor', '<email address hidden>', '<email address hidden>', '<email address hidden>', 'activities-config@nls1729', '<email address hidden>', '<email address hidden>', 'quickoverview@<email address hidden>', '<email address hidden>']"

2. If the problem persists then please try to send us a video of it.

3. Please also run 'lspci -k' and send us the output.

[Pedro Côrte-Real (pedrocr)]

This is really easy to reproduce. Just arrange your screens so your external screen is above the internal one instead of to the left or right. Now when you switch virtual desktops the contents are moved through the external screen.

[Launchpad Janitor (janitor)]

[Expired for gnome-shell (Ubuntu) because there has been no activity for 60 days.]

[Pedro Côrte-Real (pedrocr)]

I've disabled all extensions and recorded a video. Here's the output of lspci:

$ lspci -k
00:00.0 Host bridge: Intel Corporation Skylake Host Bridge/DRAM Registers (rev 08)
 Subsystem: Lenovo Xeon E3-1200 v5/E3-1500 v5/6th Gen Core Processor Host Bridge/DRAM Registers
 Kernel driver in use: skl_uncore
00:02.0 VGA compatible controller: Intel Corporation HD Graphics 520 (rev 07)
 Subsystem: Lenovo Skylake GT2 [HD Graphics 520]
 Kernel driver in use: i915
 Kernel modules: i915
00:08.0 System peripheral: Intel Corporation Skylake Gaussian Mixture Model
 Subsystem: Lenovo Xeon E3-1200 v5/v6 / E3-1500 v5 / 6th/7th Gen Core Processor Gaussian Mixture Model
00:14.0 USB controller: Intel Corporation Sunrise Point-LP USB 3.0 xHCI Controller (rev 21)
 Subsystem: Lenovo Sunrise Point-LP USB 3.0 xHCI Controller
 Kernel driver in use: xhci_hcd
00:14.2 Signal processing controller: Intel Corporation Sunrise Point-LP Thermal subsystem (rev 21)
 Subsystem: Lenovo Sunrise Point-LP Thermal subsystem
 Kernel driver in use: intel_pch_thermal
 Kernel modules: intel_pch_thermal
00:16.0 Communication controller: Intel Corporation Sunrise Point-LP CSME HECI #1 (rev 21)
 Subsystem: Lenovo Sunrise Point-LP CSME HECI
 Kernel driver in use: mei_me
 Kernel modules: mei_me
00:17.0 SATA controller: Intel Corporation Sunrise Point-LP SATA Controller [AHCI mode] (rev 21)
 Subsystem: Lenovo Sunrise Point-LP SATA Controller [AHCI mode]
 Kernel driver in use: ahci
 Kernel modules: ahci
00:1c.0 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port (rev f1)
 Kernel driver in use: pcieport
 Kernel modules: shpchp
00:1c.2 PCI bridge: Intel Corporation Sunrise Point-LP PCI Express Root Port (rev f1)
 Kernel driver in use: pcieport
 Kernel modules: shpchp
00:1f.0 ISA bridge: Intel Corporation Sunrise Point-LP LPC Controller (rev 21)
 Subsystem: Lenovo Sunrise Point-LP LPC Controller
00:1f.2 Memory controller: Intel Corporation Sunrise Point-LP PMC (rev 21)
 Subsystem: Lenovo Sunrise Point-LP PMC
00:1f.3 Audio device: Intel Corporation Sunrise Point-LP HD Audio (rev 21)
 Subsystem: Lenovo Sunrise Point-LP HD Audio
 Kernel driver in use: snd_hda_intel
 Kernel modules: snd_hda_intel, snd_soc_skl
00:1f.4 SMBus: Intel Corporation Sunrise Point-LP SMBus (rev 21)
 Subsystem: Lenovo Sunrise Point-LP SMBus
 Kernel modules: i2c_i801
00:1f.6 Ethernet controller: Intel Corporation Ethernet Connection I219-V (rev 21)
 Subsystem: Lenovo Ethernet Connection I219-V
 Kernel driver in use: e1000e
 Kernel modules: e1000e
02:00.0 Unassigned class [ff00]: Realtek Semiconductor Co., Ltd. RTS522A PCI Express Card Reader (rev 01)
 Subsystem: Lenovo RTS522A PCI Express Card Reader
 Kernel driver in use: rtsx_pci
 Kernel modules: rtsx_pci
04:00.0 Network controller: Intel Corporation Wireless 8260 (rev 3a)
 Subsystem: Intel Corporation Wireless 8260
 Kernel driver in use: iwlwifi
 Kernel modules: iwlwifi

[Daniel van Vugt (vanvugt)]

Bizarrely I /think/ that might be correct behaviour.

By default workspaces do not span all displays. So as you scroll between workspaces you probably will and should see windows from one display fly over the other. Because workspaces don't span all displays by default.

Not completely sure since I haven't tried using multiple monitors with multiple workspaces myself.

Have a look in gnome-tweaks and see if "Workspaces span displays" improves things at all...?

[Pedro Côrte-Real (pedrocr)]

Of course "Workspaces span displays" fixes it as everything moves at once. Putting the external screen on the left or right also fixes it. But that just shows how the animation is broken. When the screen is on top and doesn't span displays there's no reason for the contents of the internal screen that are switching virtual desktop to fly through the external screen. That's just a bug.

[Daniel van Vugt (vanvugt)]

I don't think it is really a bug.

Workspace switching is a smooth(ish) animation. Not instantaneous. As part of that animation, windows from the old workspace fly out and windows from the new workspace fly in. If your monitors are arranged vertically then this means the windows are indeed flying over the other monitor that's not switching.

Possible solutions would be:

 (a) Gnome Tweaks > Appearance > Animations = OFF ; or
 (b) Arrange your monitors horizontally ; or
 (c) Ask Gnome for a new feature to arrange workspaces horizontally ; or
 (d) Ask Gnome to hide windows from the other monitor during switch animations.

If you wish to go ahead with (c) or (d) then please report it at https://gitlab.gnome.org/GNOME/gnome-shell/issues
and let us know the ID of the new bug.

[Pedro Côrte-Real (pedrocr)]

>As part of that animation, windows from the old workspace fly out and windows from the new workspace fly in.

This makes perfect sense but there's no reason for that flying to happen over the external screen as that one isn't changing at all. None of those windows will ever stop in that space so it's just a strange movement of windows across screen real estate they never belong to.

I've already disabled animations to not have to deal with this. But the number of tweaks and extensions I've already had to do to get a semi-acceptable gnome-shell experience is amazing...

[Pedro Côrte-Real (pedrocr)]

Here's the upstream issue:

https://gitlab.gnome.org/GNOME/gnome-shell/issues/455