Re: Need hints trying to locate a compositing issue.

Howdy,

On 9/23/20 11:09 PM, Nikolai Zhubr wrote:
> Hi all,
> 
> Sorry if this is not the best place to ask, feel free to point me to a 
> better one if necessary.
> 
> I'm using KDE 4.11 which came with my opensuse 13.2. Sure it is a pretty 
> old system but it still does its job fine every day and I plan to keep 
> it for some while. I've made quite a lot of updates to support newer 
> hardware etc.
> 
> Now to the point. I have desktop effects enabled (desktop cube, woobly 
> windows, etc) for years and had nothing wrong with it. The video adapter 
> is Intel HD (builtin), OpenGL works fine. Now I've found a reliably 
> reproducable issue. When I connect to a remote windows box using RDP and 
> start picture/fax viewer in it and then scroll the picture up/down 
> rapidly several times inside this remote picture/fax viewer while 
> simultaneously moving mouse around aggressively, an artifact appears. It 
> looks as if 2 flip-pages of window contents buffer being repeatedly 
> interchanged as mouse approaches control buttons (and some small 
> repainting therefore needs to happen) AND one of this pages then 
> exhibits a vertically misplaced portion of the picture, so part of the 
> window looks "flashing" rapidly until I stop moving the mouse. It feels 
> a bit like maybe some memory corruption so I'd like to try find and fix it.
> The issue does not happen with Desktop Effects disabled or set to 
> XRender, therefore I suppose the RDP application is not to blame. 
> Obviously it is related to OpenGL and compositing and vertical block 
> movement. Now my suspect list is the following:

Have you tried disabling buffer age support? 
https://community.kde.org/KWin/Environment_Variables#KWIN_USE_BUFFER_AGE

My wild guess is that kwin's command stream is not synchronized with the 
X command stream.

Cheers,
Vlad

> 1. kernel 4.14.174 - buggy drm module?
> 2. libdrm 2.4.67 - buggy library?
> 3. Mesa 11.2.2 - buggy library?
> 4. xorg 1.16.1 - buggy X?
> 5. intel X module 48.20200205.fc33 (from Fedora core 33) - buggy intel 
> driver?
> 6. kwin 4.11.20 - buggy compositor?
> 
> So pretty large list, and I'm not sure how to better dig it further. Any 
> hints greatly appreciated. Maybe it is a known issue already?
> 
> Thanks.
> 
> Regards,
> Nikolai