Xfce Forum

VinzC

Member

From: Belgium

Registered: 2011-01-01

Posts: 17

PBM: Screen ghosting effects with nouveau when compositor is enabled

Hi all.

I'm a Gentoo user since 2004 and I have a laptop with nVidia optimus technology. I have disabled the embedded Intel video card however, to leave the nVidia adapter as my only working video card.

I have an issue with nouveau when the compositor is enabled. The question is I don't know whether it relates to the kernel module or the compositor, so please help me identify the root cause so that I can file a bug by the appropriate maintainers.

Now to my issue. I work with virtual desktops, one or two of which are used for full-screen windows. Geany is one of them and I regularly work with that software. I also have a web browser, namely Seamonkey. The issue is described as follows:

whenever I leave Seamonkey with a Youtube video playing in the active tab and I switch to Geany, the entire display is covered (or overlayed) with a ghost image of a previously displayed desktop or program. Sometimes the overlay image is that of the screensaver right before I unlocked it. Sometimes it can be the image of Geany itself. It can be a random image but it is always a complete image of what the display has previously showed.

Here's what appears instead of Geany while a video is playing in Seamonkey:
And no, it's not some trick of mine! it's not some image manipulation either (apart from the two sensitive items I wanted redacted)! Geany is completely hindered behind this. And even worse, the fact that xfce4-screenshooter took a screenshot of what was appearing on the screen means to me the *entire* video memory (or whatever it is) got corrupted like this — i.e. I didn't need an external camera to take this screenshot.

Note that sometimes the blinking cursor appears but this is not the case here. This happens on a virtual desktop basis. Switching virtual desktops makes the overlay ghost disappear but sometimes it reappears after a short while.

On the above screenshot the video that appears is not even the one that was playing when I took the screenshot! It's a video that I had played a few minutes ago. And, as you can see the full-screen video is itself garbled with the restored Seamonkey window, playing that video — as I mentioned: it can be a composition with several screens that appeared before.

It doesn't happen only with Geany but [Geany full screen] + [Seamonkey playing a Youtube video in the active tab] is a use case that triggers the issue every time.

Here's another example, Geany garbled with some remnants of my screensave unlock window and some notice from xscreensaver (login name redacted) :

Here's what should appear instead (same virtual desktop):

If I disable the compositor in Xfce "Window tweaks", the issue disappears. I described the problem in Gentoo forums.

So I'd like to know: is it a bug in nouveau? or is it a bug in X compositor? or is it both? or something else?

As I mentioned: I want to file a bug but I need to know where exactly. It's been more than one year I'm facing this bug and have started to change my habits to live with it, you get the picture.

Thanks in advance for your help.

Last edited by VinzC (2018-08-22 18:13:28)

CwF

Member

Registered: 2018-01-28

Posts: 305

Re: PBM: Screen ghosting effects with nouveau when compositor is enabled

I think I've seen this, look for and disable "shadows" options in the compositor. maybe...

VinzC

Member

From: Belgium

Registered: 2011-01-01

Posts: 17

Re: PBM: Screen ghosting effects with nouveau when compositor is enabled

I think I've seen this, look for and disable "shadows" options in the compositor. maybe...

Done that. Doesn't work. The only way is to disable compositing entirely.

MountainDewManiac

Member

From: Where Mr. Bankruptcy is Prez

Registered: 2013-03-24

Posts: 1,115

Re: PBM: Screen ghosting effects with nouveau when compositor is enabled

Do you still observe this issue if you use nVidia's video driver instead of the Nouveau one?

Regards,
MDM

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How to Ask for Help <=== Click on this link

alcornoqui

Member

Registered: 2014-07-28

Posts: 832

Re: PBM: Screen ghosting effects with nouveau when compositor is enabled

Don't know if it'll help, but I use this command when I want to disable transparency for a single window:

xprop -f _NET_WM_WINDOW_OPACITY_LOCKED 32c -set _NET_WM_WINDOW_OPACITY_LOCKED 1

I got it from this thread.

Good luck!

VinzC

Member

From: Belgium

Registered: 2011-01-01

Posts: 17

Re: PBM: Screen ghosting effects with nouveau when compositor is enabled

Do you still observe this issue if you use nVidia's video driver instead of the Nouveau one?

Regards,
MDM

No, I don't. It only happens with nouveau.

Don't know if it'll help, but I use this command when I want to disable transparency for a single window:

xprop -f _NET_WM_WINDOW_OPACITY_LOCKED 32c -set _NET_WM_WINDOW_OPACITY_LOCKED 1

I got it from this thread.

Good luck!

Thanks for the hint but I fail to understand if/how it would solve this issue. For instance, how do I determine what window(s) to make opaque/transparent? Besides with every compositor's option turned off, the problem still occurs. Even with transparency turned off the problem still occurs; I need to turn the compositor off to not experience this bug so I doubt adjusting transparency is likely to fix anything.

My technical understanding is about how video rendering is done through the compositor's buffers, which I deduced from seeing what screen corruptions do, how, and when. When the compositor is enabled, transparency happens through [what I'd call] the compositor's video "buffers" so it's highly unlikely that disabling transparency would cure the issue iif the problem lies with the compositor. But I might be wrong, of course.

Karadoc

Member

Registered: 2019-06-26

Posts: 1

Re: PBM: Screen ghosting effects with nouveau when compositor is enabled

Hello,
I have the very same issue since I had to change from NVidia proprietary drivers to Nouveau drivers. I'm using an up to date Arch Linux.
I'm very happy to see I'm not alone with this problem (I first thought it was due to a bug in Mesa/Nouveau but couldn't manage to find any reference of such issue in the FreeDesktop bugtracker).
The Xorg.0.log doesn't have any line about this issue.
I found this old bug in the XFCE bugtracker, that seems relevant to our situation, but without a decent answer : https://bugzilla.xfce.org/show_bug.cgi?id=12890
I had to fully disable the compositing (it was a nightmare to minimize/maximize the windows each time the ghost buffered screen was reloaded), but there really is a bug there.

My NVidia card is a Quadro FX 580 (G96CGL)

Regards