- xscreensaver+gdmflexiserver work well, it automatically locks, but clicking on "New Login" presented by xscreensaver it fails with the message about gdmflexiserver no longer being supported. This makes letting other users log in practically impossible.
- gnome-screensaver never automatically locks. I can lock it with Win+L, and everything is OK. But if I forget to lock it when I leave my desk, the screensaver does not lock, no matter what options I have in gnome-screensaver-preferences or gnome-power-manager.
I read in #538694 that the problem is in versions of gnome-screensaver after 2.26. In all later versions, gnome-screensaver relies on the the idle time reported by gnome-session. I have GNOME installed, since other users use it, but I don't want to start a full GNOME session just so gnome-screensaver will lock. Activating the screensaver isn't necessary (since I have it set to blank, anyway). I've had to play with the DPMS settings, so the screen blanks automatically but does not lock. So essentially this is a security issue for me. If I could figure a way to run gnome-session without starting a full GNOME-session, I think it could work. In the bug report I found, someone said they were able to workaround the problem by only installing gnome-session-bin, but this will not work for me since the other users of the system use GNOME.
The xscreensaver+gdmflexiserver is a problem, but it's not a security problem. I am the primary user of this machine, so using this option would work well for me 95% of the time. It's when others want to use my computer that this becomes an issue. I don't want them to reboot the machine while I'm not here, but I want them to be able to launch their own GNOME session without impinging on my normal session.
I only need a solution to one problem; if I solve one of the above problems the other problem will become immaterial. If another display manger (e.g. Slim) would work better for this purpose, by all means recommend it.