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I am not familiar with bpftrace (though that does look extremely potent), but XSetSelectionOwner is called when an application wants to make data available via the clipboard, not access it. Also not sure if that would also catch stuff with Xlib, and I guess it won't if it's statically linked (this is why I pivoted hax11 from hooking library calls to MITM-ing the connection).

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My bad, I actually had the "production" trace command set to look for `XGetSelectionOwner`, but mis-pasted into my comment ;) Will that fare any better? It did make a few more PIDs/culprits end up in the trace output for me after all.

You are correct that "bringing your own function"/shared object will break that particular bpftrace script, but I would assume one could find a way to set up a probe in the X server, where all clients messing with clipboard state via some kind of IPC have to pass thru? (Again, I can only wildly speculate how X11 works under the hood - kinda shameful that I never bothered to look over all these years :-S )

I think XConvertSelection would be more effective. Applications which use the XFixes extension to receive notifications of new owners won't need to use XGetSelectionOwner.

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