Re-opening this issue as it is not 100% solved and understood...

The situation is: with extensions XFIXES enabled in nxagent/x2goagent   
we observe KDE crashes on Ubuntu precise and above. The crashes happen  
  in kwin.

The problem could be tracked down to some problems in libxfixes. The   
change must have been between libxfixes from oneiric and libxfixes   
from precise.

On IRC I wrote this about the observed issue:

15:48 < sunweaver> siretart: I might have found the libxfixes issue   
with libxfixes since precise...
15:48 < sunweaver> at least I have several question marks...
15:49 < sunweaver> the xserver-xorg src package in precise has a patch  
  named: 500_pointer_barrier_thresholds.diff
15:50 < sunweaver> this patches in xfixes v6 code into the xfixes v5 extension
15:51 < sunweaver> in that patch you can also see that the xfixes   
extension version is also incremented (5 -> 6)
15:52 < sunweaver> the libxfixes 1:5.0-4ubuntu4 and the package   
x11proto-fixes-dev 1:5.0-2ubuntu1 package also have patches for this   
improvement: both named
                    01_fixesproto-v6.diff.
15:54 < sunweaver> However, when looking at a build of libxfixes   
5.0-4ubuntu4 I see a config.h file that announces itself with   
PACKAGE_VERSION 5.0.
15:55 < sunweaver> So, my current guess is that libxfixes annouces   
itself as v5 and also does a xlib-xserver version handshake based on   
v5, but then
                    executes code from libxfixes v6 which then breaks nxagent.
15:55 < sunweaver> Is that possible?

Can anyone comment on this?

Mike

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