I have installed the Bullseye for the testing, and i have noticed that UI is smooth and there is NO screen tearing at all. (But the other things, which works in buster are problematic here on Bullseye...)
On the Buster there is screen tearing, which make me crazy... and my Question is:
Whats the difference between Bullseye vs Buster? and how can eliminate screen tearing in Buster please? Is it possible please?
Thanks
This probably has to do with two things:
They've switched to a compositing window manager in anticipation of adopting Wayland.
They've also (from the same article) started using the in-kernel KMS video driver, which is generally considered a better idea than not using it. This implies to me they did some work on the GPU specific driver, but I did not look into that further.
As to which is most responsible, I'd guess the latter but that is just an off-the-cuff guess.
how can eliminate screen tearing in Buster
This is really a separate question, since you can't do it just by making the two changes just described -- or at least, not the second one.1
You could try switching to mutter (the new window manager) but this may have detrimental effects on the desktop environment (DE).2 You could also look around for an existing widely used DE/WM combination that includes a compositing window manager, of which I think there are probably a decent handful available in RpiOS since they would be in Debian upstream.
However, this will mean a completely new desktop and probably one which uses a bit more CPU/GPU -- and I can't promise it will make the difference, as I've already said I think the KMS driver is mostly responsible.
It probably isn't impossible, but I think will require some skills and knowledge not possessed by the average pi user.
I have an explanation of the linux GUI desktop stack that goes through the relationship between these various parts.
