lock screen without screensaver as a hotkey

[Peter Volkov <pva gentoo org>]

Hi!

I would like to code a bit and fix the problem I have:
Lock screen functionality works if I press "username" button in right
top angle and then "Lock screen". But whenever I try to lock the screen
with hotkey it does nothing. I've checked gnome-control-center sources
and lock button shell extension sources and found that shell extension
button (it works btw) calls: 
Main.screenShield.lock(true)
while hotkey is binded to some screensaver functionality that is not
installed on my laptop. I'd like to fix this correctly and thus I'm
looking for a hint(s) on what to do next. Could you suggest best course
of actions to fix this problem? I guess it's best to have some general
"lock screen" functionality that'll call screensaver's lock and if that
fall back on screenShield.lock() but what do you think?

Thanks in advance for any pointers,
--
Peter.