Bug 433813

Firefox and VSCode define what Ctrl+Tab does for themselves. Plasma or any other KDE software has no impact on it. You'd need to report this to them. Thanks!

I already reported this issue in Firefox (https://bugzilla.mozilla.org/show_bug.cgi?id=1695416), the maintainer tried to reproduce it on Ubuntu with Gnome and it worked there correctly. I also tried it in Gnome myself, and it worked there correctly. Furthermore, VS Code is also affected on KDE. This led me to the conclusion that it's a KDE-specific issue because it affects multiple applications and it works correctly on different platforms.

Unless I'm misunderstanding the original bug report, there is 0% chance that any KDE code is affecting this. We don't have anything that alters the way Ctrl+Tab works for 3rd-party apps.

Maybe you can attach a screen recording that shows the problem?

Here's the video (https://drive.google.com/file/d/1kimGpEYPm3pwoLxYKRQhcrAfym70Db1r/view), but it won't tell you much. The problem is, as I already said, that Ctrl-Tab brings up the pop-up window with thumbnails of tabs, however this pop-up remains on-screen even after I *release* Ctrl button. This does not happen on any other DE (Windows or Gnome). I have a fresh installation KDE, so I it's highly unlikely that I messed up with the configuration. Anyone with KDE and Firefox or VS Code can reproduce this behaviour.

My Firefox doesn't have that effect when I cycle through tabs with Ctrl+Tab. Is that functionality provided by a 3rd-prty add-on or something?

Created attachment 136334 [details]
KDE keyboard settings: Caps Lock as Ctrl

Thanks a lot for looking it! After you tried it, I realised that the problem is due to me using Caps Lock as Ctrl. When using the actual Ctrl key, I get the correct behavior: releasing the Ctrl key switches the tab as expected.

Having said that, I remapped Caps Lock to Ctrl in the KDE System Settings app (see the attached screenshot). And I believe that the issue is that while Caps Lock acts as Ctrl when pressing the key, it doesn't do so when *releasing* the key, which is verified by the incorrect behavior in Firefox and VS Code applications that utilise releasing of Ctrl.

I tried remapping Caps Lock to Ctrl with the command `setxkbmap -option ctrl:nocaps` and I get correct behavior when releasing the key. So I still believe it's a problem that needs to be addressed on the KDE side, in the System Settings for keyboard.

Thanks for narrowing that down.

Still, I'm wondering where you got that fancy visualization for your Firefox tab switcher. I won't be able to confirm the issue until I can get that to appear for myself.

Hi Nate,

It's hard for me to say, this windows has always been there for me. Maybe because I recycle the my own configuration. Here are the relevant Firefox settings:

browser.ctrlTab.recentlyUsedOrder: True
services.sync.prefs.sync.browser.ctrlTab.recentlyUsedOrder: True

Also, make sure to hold Ctrl after pressing Ctrl-Tab, this window takes a second to pop up.

If you still cannot reproduce it in Firefox, you could try Visual Studio Code - just recycle last opened editor tabs with Ctrl-Tab, here is a screengrab:

https://drive.google.com/file/d/12ddThuxndNbXeNR5ZVYwvIKWLZxV5SSe/view

I just checked, Atom editor also cycles between recent editor tabs with Ctrl-Tab.

Are you using Plasma on X11 or Plasma on Wayland?

Hi, Vlad. I am using Plasma on X11 with NVIDIA proprietary drivers if that helps.

Upgraded to Plasma 5.25.5 and the bug is still there.

OK, I found out what I've been doing wrong. There are two ways to map CAPS LOCK to CTRL: one is "Caps Lock behavior -> Make Caps Lock an additional Ctrl" and another one "Ctrl Position -> Caps Lock as Ctrl". The issue I reported only affected the former option while the latter one works correctly. This is a bit confusing but works for me, hence closing the issue.