Gnome on Xorg freezes for short time on every keyboard layout switch.

[Marat]

This happens on Ubuntu 18.04 only on Gnome and only on Xorg.
I use non-default shortcut for keyboard layout switching. I've tried CapsLock and Alt+Shift for this. I configured this shortcut through Gnome Tweaks. It's important, because when I use default shortcut (super+space, for some reason it is still present, even if you have configured different shortcut using Gnome Tweaks) the behaviour is different - there is still a delay, but there is also a layout switching window, and there is no whole Gnome freeze. There is already bugreport for that (https://bugs.launchpad.net/ubuntu/+source/gnome-control-center/+bug/1754702)

When switching keyboard layout with a non-default shortcut (e.g. CapsLock) gnome freezes for about half a second. This is an annoyance when typing.
In fact, for a short period of time whole GUI is frozen. If you'll just switch keyboard layout as fast as you can, you'll see, that GUI will freeze for some time and Xorg would eat most of CPU. If you run a movie player during that time (e.g. VLC or Videos) you'll notice, that while video is frozen or stutters horribly, sound is perfectly normal. The GUI will unfreeze soon after you stop switching keyboard layouts.

I have two keyboard layouts configured: EN and RU.

I've seen this bug on two different notebooks with Ubuntu 18.04. My friend also confirmed the same bug on Fedora with Gnome 3.28.

This bug does NOT affect Gnome on Wayland, nor MATE, nor Cinnamon. I have not tried KDE.

Here is a link of short screengrab, illustrating the issue, in this video I'm trying to type as fast as I can, while occasionally switching keyboard layout.
https://streamable.com/ue2um

Here is a link of the same, but with a Gnome on Wayland, there is no problem there:
https://streamable.com/vdr1d

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Nikolay Vinogradov (nikolay.vinogradov)]

Same issue here, bionic 18.04, nvidia optimus laptop, xorg (no wayland), super+space for layout switching.