Hi Tristan and X2Go devs,
I tested a KDE session, and the system tray icons successfully showed up under the KDE system tray. I tested both Kopete and KTorrent.
I attached the command-line output from this. (KWrite does not use a system tray icon. I ran KWrite anyway as a test.)
I was *unable* to reproduce this bug when using regular X11 forwarding (ssh -Y hostname) on an Ubuntu 14.04 machine running MATE 1.8.0. Under this configuration, the system tray icons successfully show up in the MATE system tray. I tested both Kopete and KTorrent.
Based on 1, 2 and 3, this bug may be a limitation of VcXsrv (our X server that runs on Windows) and Cygwin XWin rather than nxagent. VcXsrv and Cygwin XWin share a lot of code in common. If we prove this to be the case, we should keep this bug open as a "known issue" and reassign it to package x2goclient. (We may also fix the bug in VcXsrv too.)
Also, I will report this to the Cygwin/X mailing list. (Cygwin and Cygwin/X use their mailing lists to track bugs.)
Test Server: the xsession script)
Test Client 1: optional updates installed
Test Client 2: optional updates installed
Test Client 3: packages installed
-Mike#2