Activating dual display only after authentication

[pedrito]

Hi all.
I wonder if I could change the behavior of the dual-display : i want it activated only when my user session is started / unlocked and that it can't apply when I logout / session is locked / before login . What would be for you guys the smartest way to do that ?
I tried to find out in my process monitor the process that manages the dual-display but could not find it...  :'(

[pedrito]

I have just got that the multi display is managed by lightDM. What if I disabled the light DM service and just added it to my session startup applications ? Could it work for my purpose ? the related machine is a sensitive PC in production and I would rather not f*** up the display when testing something, so your opinion is very welcome :-)