Bug 335265

Summary: vsync doesn't work with OSS radeon and swapbufferswait off
Product: [Plasma] kwin Reporter: empire
Component: scene-openglAssignee: KWin default assignee <kwin-bugs-null>
Status: RESOLVED WORKSFORME    
Severity: major CC: empire, kde.org
Priority: NOR    
Version First Reported In: 4.11.9   
Target Milestone: ---   
Platform: Arch Linux   
OS: Linux   
Latest Commit: Version Fixed/Implemented In:
Sentry Crash Report:

Description empire 2014-05-24 09:28:29 UTC 
When using the open source radeon driver, if I disable the swapbufferswait driver option vsync does not work with kwin and I get a lot of tearing. I tried all settings in system settings -> desktop effects -> advanced -> tearing Prevention (VSync) but none eliminate tearing. (option re-use screen content does not work at all, it freezes my output, but that is another bug)

I don't want to use swapbufferswait, because it forces vsync on opengl everywhere, and I like to need it to be disabled for some opengl applications (wine games).

Reproducible: Always

Steps to Reproduce:
1. add Option      "SwapbuffersWait"   "off" in device section of xorg.conf
2. start kde
3. choose system settings -> desktop effects -> advanced -> tearing Prevention (VSync) to something other than "none" or "re-use screen content"
3. move windows around
Actual Results:  
tearing

Expected Results:  
no tearing
Comment 1 empire 2014-05-24 09:31:24 UTC 
Actually "Full screen repaints" work, but it is very slow (the windows lag many frames behind the mouse cursor) and therefore it is unusable. I know it is not recommended for the open source drivers.
Comment 2 Thomas Lübking 2014-05-24 11:48:01 UTC 
- "Full screen repaints" is the only way to get VSync on MESA*
- Only when cheap does what it says: it only syncs when you're "nearly"™ repainting the entire screen anyway (video playback)
- "Re-Use screen contents" would work, but DO NOT TOUCH THAT! If you ever do, RESTART kwin afterwards (the driver will likely enter a VERY SLOW mode when attempting to read from GL_FRONT) "kwin --replace &" (thus the big, fat warning in the config dialog ;-)

*unless the driver already supports GLX_EXT_buffer_age,  check "glxinfo | grep GLX_EXT_buffer_age"

Default should be "only when cheap", "full screen" should work, but will likely suffer from blurring.
Comment 3 kde.org 2021-11-06 17:30:34 UTC 
This issue report is quite old. Can you please confirm, that it still persists with KDE 5.23?
Comment 4 Bug Janitor Service 2021-11-21 04:38:51 UTC 
Dear Bug Submitter,

This bug has been in NEEDSINFO status with no change for at least
15 days. Please provide the requested information as soon as
possible and set the bug status as REPORTED. Due to regular bug
tracker maintenance, if the bug is still in NEEDSINFO status with
no change in 30 days the bug will be closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

If you have already provided the requested information, please
mark the bug as REPORTED so that the KDE team knows that the bug is
ready to be confirmed.

Thank you for helping us make KDE software even better for everyone!
Comment 5 Bug Janitor Service 2021-12-06 04:38:14 UTC 
This bug has been in NEEDSINFO status with no change for at least
30 days. The bug is now closed as RESOLVED > WORKSFORME
due to lack of needed information.

For more information about our bug triaging procedures please read the
wiki located here:
https://community.kde.org/Guidelines_and_HOWTOs/Bug_triaging

Thank you for helping us make KDE software even better for everyone!