gnome: how to execute commands upon screensaver activation?

is there a way to run a specific command every time gnome-scree开发者_如何学JAVAnsaver is activated?

thanks

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Found there : http://people.gnome.org/~mccann/gnome-screensaver/docs/gnome-screensaver.html#gs-intro

Gnome Screensaver has a Dbus Signal named :

ActiveChanged

in

org.gnome.ScreenSaver

then call

GetActive()

and if it returns true you call your method