Fixing Tearing with Kubuntu 13.04 and nVidia 304.88

UPDATE 26th May 2014: I tried this same fix on Kubuntu 14.04, and it black-screened the system. I'd also been tinkering with some other stuff at the same time, so haven't tracked it down exactly (or what the new fix might be), but I suspect it is the GL_YIELD change to /etc/profile below. I don't recommend doing it unless you're ready to rollback/recover the original.. UPDATE 20th Oct 2014: Tried a very similar fix on 14.04 and this time it worked, so not sure what was going on here.

After finding a workaround to fix tearing on Mint 15 Cinnamon, I jumped to Kubuntu 13.04 because there were some strange issues with screen recording in Mint, I assume because of the tearing workaround affected some of the internals in the graphics stack that screen capture uses.

Unfortunately, Kubuntu had the same tearing issue that Xubuntu exhibited. The solution again was a workaround, but different:

• Install KDE 4.11 as per the instructions at this noobslab article:

  sudo add-apt-repository ppa:kubuntu-ppa/backports
  sudo apt-get update
  sudo apt-get dist-upgrade

  (Not sure if this was actually necessary, but it was one of the other things I tried first).
• In "Desktop Effects -- KDE Control Module" => Advanced tab, set Compositing type to "OpenGL 3.1" and Tearing Prevention (VSync) to "Re-use screen content".
• Add:

  export __GL_YIELD="USLEEP"

  To /etc/profile as per this KDE forum post. _{NOTE: But see above regarding this possibly having problems in more recent versions}.

That should fix the tearing.

Note on Fullscreen Games

For some reason, the above worked in the general desktop environment, but fullscreen games were still tearing. The fix that worked in that case was to uncheck "Suspend desktop effects for fullscreen windows". Not sure why that made things better, since I would have thought the other way around would work, but that's the change that fixed it.

Things That Didn't Work

For reference, here are the things I tried that didn't work:

• Turn off compositing with Alt+Shift+F12 (no effect).
• Install KDE 4.11 (as noted above, this by itself didn't help, but may be necessary for the workaround).
• Install compiz. The tearing was perhaps a little better, but still not great, and compiz just doesn't look as good as kwin.

And one last resort I would have tried eventually: Re-compiling KDE with this patch.