Like @kshegunov already wrote using singleton should be avoided when possible and your use case really does't need any singleton.

It sounds that you are rather creating tight coupling between your different classes rather that have a lean path to use system tray.

So what are all these classes doing with the system tray icon and that menu ?

I have the same issue with updating the context menu with Qt 5.6 on Ubuntu 16.04 KDE Neo.

I tested in Ubuntu 14.04 up to 15.10 and the tray icon is still not shown. The systray whitelist is not available any more in those distributions though, and I'd rather not have to install packages that bring back the tray icon like https://launchpad.net/~gurqn/+archive/ubuntu/systray-trusty. I thought Qt 5.4.2 already supported app indicators?

OK, we found how to use -bundle...
https://developer.apple.com/library/mac/documentation/Porting/Conceptual/PortingUnix/compiling/compiling.html

By reading the documentation I linked to and the examples also available from Qt. The "System Tray Icon" example is a good start.

Good, glad ya got it sorted out. Sorry I've been super busy lately and haven't lurked the forums here. :)

@Wieland Thanks for the reply. I'll verify with Ubuntu GNOME to see if the fix has been backported to Ubuntu.

For future reference: I'm using the libraries provided by the official Ubuntu repositories.