XFCE 4.10 shutdown commands on Ubuntu 12.04 LTS

Question

ubuntu

Good evening!
Given: Work computer running XFCE 4.10 To complete the work, I use the Logout menu .

Task: execute additionally some command when pressing any button from this menu and, if possible, add your own.
Question 1: how to find out what specifically and exactly happens when any of these buttons is pressed (for example, in the /etc/AAA file in the BBB section, the prescribed CCC command is executed)
Question 2: Depending on the state of the system (distribution kit, package sets, installed drivers and etc.) these buttons are "gray", inactive and, accordingly, unavailable for use. How to find out where the settings for the availability / inaccessibility of these buttons are registered.

Answer 1

What graphical environment is used? If LightDM then you can try this solution
LightDM login and logout scripts