Bug 451708

Summary: Plasma UI elements are always transparent in a VM
Product: [Plasma] plasmashell Reporter: Alistair Buxton <a.j.buxton>
Component: generalAssignee: Plasma Bugs List <plasma-bugs-null>
Status: RESOLVED NOT A BUG    
Severity: normal CC: kde, lemmyg, mikel5764, nate, noahadvs
Priority: NOR    
Version First Reported In: master   
Target Milestone: 1.0   
Platform: Other   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:
Attachments: Screenshot showing the background clearly showing through the launcher

Description Alistair Buxton 2022-03-19 23:49:40 UTC
STEPS TO REPRODUCE
1. Right click panel -> edit mode
2. Click "more options..." then set opacity to "opaque".
3. Exit edit mode and open the application launcher.

OBSERVED RESULT
Launcher has a slightly transparent background

EXPECTED RESULT
Launcher should not have a transparent background

SOFTWARE/OS VERSIONS
Kde Neon developer live image as of day of bug report
Comment 1 Alistair Buxton 2022-03-19 23:52:01 UTC
Also affects the alternative "Application Menu" launcher.
Comment 2 Alistair Buxton 2022-03-19 23:57:01 UTC
Created attachment 147606 [details]
Screenshot showing the background clearly showing through the launcher
Comment 3 galder 2022-03-20 09:34:22 UTC
Hello,
could you please provide details of your computer environment.
Graphical platform etc...
Regards
Comment 4 Alistair Buxton 2022-03-20 12:30:07 UTC
(In reply to galder from comment #3)
> Hello,
> could you please provide details of your computer environment.
> Graphical platform etc...
> Regards

Quickemu 3.11 using /usr/bin/qemu-system-x86_64 v6.0.0
 - Host:     Ubuntu 20.04.3 LTS running Linux 5.4 (al-desktop)
 - CPU:      Intel(R) Core(TM) i7-6700 CPU @ 3.40GHz
 - CPU VM:   1 Socket(s), 2 Core(s), 2 Thread(s), 8G RAM
 - BOOT:     EFI (Linux), OVMF (/usr/share/OVMF/OVMF_CODE_4M.fd), SecureBoot (off).
 - Disk:     kdeneon-developer/disk.qcow2 (16G)
             Just created, booting from kdeneon-developer/neon-developer-current.iso
 - Boot ISO: kdeneon-developer/neon-developer-current.iso
 - Display:  SDL, virtio-vga, GL (on), VirGL (on)
 - ssh:      On host:  ssh user@localhost -p 22220
 - SPICE:    On host:  spicy --title "kdeneon-developer" --port 5930 --spice-shared-dir /home/al/Public
 - WebDAV:   On guest: dav://localhost:9843/
 - 9P:       On guest: sudo mount -t 9p -o trans=virtio,version=9p2000.L,msize=104857600 Public-al ~/Public
 - Process:  Starting kdeneon-developer.conf as kdeneon-developer (2462784)
Comment 5 galder 2022-03-20 14:32:42 UTC
Hello,
is it x11 or Wayland session?
I tried to test Neon master in a VM but unfortunately the updating the pkgs to latest broken the VM. :)
Comment 6 Alistair Buxton 2022-03-20 14:58:50 UTC
(In reply to galder from comment #5)
> Hello,
> is it x11 or Wayland session?
> I tried to test Neon master in a VM but unfortunately the updating the pkgs
> to latest broken the VM. :)

It is X11.

Btw if you install quickemu then running latest KDE Neon image in VM can be done with two commands:

`quickget kdeneon developer && quickemu kdeneon-developer.conf`
Comment 7 galder 2022-03-20 15:12:36 UTC
Sorry I'm using Kubuntu 21.10 and virtual box to test Kde Neon.
I compiled current master plasma-desktop  and plasma-workplace in Kubuntu 21.10. 
I believe they should be responsible for the plasma panel.
The opacity and translucency works as expected for me in x11 and Wayland.
Regards
Comment 8 galder 2022-03-20 15:13:19 UTC
Operating System: Kubuntu 21.10
KDE Plasma Version: 5.24.3
KDE Frameworks Version: 5.92.0
Qt Version: 5.15.2
Kernel Version: 5.13.0-35-generic (64-bit)
Graphics Platform: X11
Processors: 8 × Intel® Core™ i7-7700HQ CPU @ 2.80GHz
Memory: 15.5 GiB of RAM
Graphics Processor: NVIDIA GeForce GTX 1060/PCIe/SSE2
Comment 9 Nate Graham 2022-03-27 16:56:41 UTC
Cannot reproduce on bare metal. Must be something to do with running in a VM.

Do other panel widget popups exhibit the same issue? Or is it only Kickoff/other launcher menus?
Comment 10 Alistair Buxton 2022-03-27 18:49:11 UTC
(In reply to Nate Graham from comment #9)
> Cannot reproduce on bare metal. Must be something to do with running in a VM.
> 
> Do other panel widget popups exhibit the same issue? Or is it only
> Kickoff/other launcher menus?

Yes, every widget popup I tried has this problem, including:

 * Application launcher
 * Application menu
 * Application dashboard
 * Calendar popup from any clock
 * Audio controls
 * Networks
 * Calculator
Comment 11 Alistair Buxton 2022-03-27 18:52:51 UTC
Also all tooltips, including the previews on the task bar, and desktop notifications.
Comment 12 Alistair Buxton 2022-03-27 19:01:48 UTC
Also the toolbar that is displayed when you edit a panel is itself transparent, regardless of the opacity setting.
Comment 13 Nate Graham 2022-03-27 21:05:13 UTC
Yep, this is a VM-related issue.

I don't know if the problem is in Plasma, or KWin.
Comment 14 Nate Graham 2025-10-17 19:05:43 UTC
Now I know. :)

The problem is that by default, most VMs don't use hardware-accelerated graphics, but the fancy blur effects require it. Software-rendering for blur effects has awful performance, so it's disabled.

Ultimately this is something you have to fix in your own VM, by manually turning on hardware-accelerated graphics.
Comment 15 Alistair Buxton 2025-10-17 19:24:19 UTC
(In reply to Nate Graham from comment #14)
> Now I know. :)
> 
> The problem is that by default, most VMs don't use hardware-accelerated
> graphics, but the fancy blur effects require it. Software-rendering for blur
> effects has awful performance, so it's disabled.
> 
> Ultimately this is something you have to fix in your own VM, by manually
> turning on hardware-accelerated graphics.

Why is blurring required for panels to NOT have transparency effects?
Comment 16 Nate Graham 2025-10-17 19:29:12 UTC
That one I can't answer, as I'm not sure.

That said, there was at one point another bug that the panel applets didn't respect the opacity setting of their parent panel, which has been fixed IIRC for Plasma 6.5.