Created attachment 143784 [details]
Demo of the problem
* Background
compton has the ability to do partial screen update. It will gather the dam=
aged
regions from Xorg, query the buffer age using GLX, and then only update the
part of the screen that is damaged.
* Problem
When partial screen update is enabled, sometimes closed window is left on t=
he
screen.=20
Please see the attachment.=20
In the clip, at first, I was repeatedly opening/closing Rofi, trying to
triggered bug (it does not reproduce consistently). After several attempts,
Rofi window is left on the screen after I closed it. Then, I moved my mouse
around to trigger updates of the window underneath.
However, if I capture a trace of this happening with apitrace, this problem
doesn't happen during the replay of the trace.
* Thoughts
Could it be mesa is returning the wrong buffer age of the back buffer?
* To reproduce
Build compton from the repo. Run it with `compton --config /dev/null
--use-damage --experimental-backends --backend glx`. Then try open/close wi=
ndow
several times.
* System info
Card: Radeon RX590
DDX: xf86-video-amdgpu
Mesa version: 19.0.0