Can't get the display in clone mode on the lightdm connection screen

[orion666]

Hello i am on Linuxmint 20.1 with Lightdm login screen manager. I have two displays in mirror mode: 1 screen in vga and 1 video projector in hdmi. Mirror mode doesn''t work with the lightdm oginscreen manager but works fine after logging user.
I would want something like this when displaying the login screen manager >xrandr --output VGA1 --mode 1280x1024 --output HDMI2 --same-as VGA1
Currently there is some files in lightdm configuration and i tried to modify the slick-greeter.conf but nothing happened.
Here is the slick-greeter.conf : (i tried to modify only-on-monitor= HDMI1 or VGA1 and then it displays the login screen manager only on the VGA screen or HDMI screen. But i don't know how to displayon the same screen at same time. Thanks you for your help.
[greeter]
active-monitor=0
activate-numlock=0
show-ally=false
theme-name=Mint-X-Brown
icon-theme-name=hicolor
stretch-background-across-monitors=false
only-on-monitor=auto
background=/usr/share/backgrounds/LM20bleu

[SMG]

You have not indicated what desktop you are using. Cinnamon has a Login Window app which permits some changes on Settings tab. Maybe there is an option there which will produce what you want.

[orion666]

I am on Linuxmint 20.1 desktop xfce. I don't find any option to run the clone mode display on the login screen. I think you can do this only by editing a file in lightdm.

[SMG]

Maybe someone with Xfce will be able to help you.