Hey !

Alors je crains de ne pas voir tout compris ! Mais ça m'intéresse évidemment.

Je tape "systemctl stop gdm" dans un terminal puis je redémarre ?

Ensuite le moniteur principal est un pc portable HP connecté en HDMI avec un moniteur ASUS. Dans "Displays", l'HP est bien configuré comme étant "Primary" et le ASUS "Secondery".

Voici un xrandr :

Screen 0: minimum 8 x 8, current 3520 x 1080, maximum 32767 x 32767
eDP1 connected primary 1600x900+0+0 (normal left inverted right x axis y axis) 344mm x 193mm
   1920x1080     60.06 +  40.04  
   1400x1050     59.98  
   1600x900      60.00* 
   1280x1024     60.02  
   1280x960      60.00  
   1368x768      60.00  
   1280x720      60.00  
   1024x768      60.00  
   1024x576      60.00  
   960x540       60.00  
   800x600       60.32    56.25  
   864x486       60.00  
   640x480       59.94  
   720x405       60.00  
   640x360       60.00  
HDMI1 connected 1920x1080+1600+0 (normal left inverted right x axis y axis) 598mm x 336mm
   1920x1080     60.00*+  50.00    59.94    59.99  
   1920x1080i    60.00    50.00    59.94  
   1600x1200     60.00  
   1680x1050     59.88  
   1280x1024     75.02    60.02  
   1440x900      59.90  
   1280x960      60.00  
   1366x768      59.79  
   1152x864      75.00  
   1280x720      60.00    50.00    59.94  
   1024x768      75.08    70.07    60.00  
   832x624       74.55  
   800x600       72.19    75.00    60.32    56.25  
   720x576       50.00  
   720x480       60.00    59.94  
   640x480       75.00    72.81    66.67    60.00    59.94  
   720x400       70.08  
VIRTUAL1 disconnected (normal left inverted right x axis y axis)

Enfin, je ne connais pas encore Xorg.conf, je vais me renseigner mais du coup je ne vois pas où copier tes dernieres lignes :

Section "ServerLayout"
    Identifier     "Layout0"
    Screen      0  "Screen0"
    Screen      1  "Screen1" RightOf "Screen0"
    InputDevice    "Keyboard0" "CoreKeyboard"
    InputDevice    "Mouse0" "CorePointer"
EndSection

...
Section "InputDevice"

    # generated from default
    Identifier     "Mouse0"


...
Section "Monitor"
    Identifier     "Monitor0"
    VendorName     "Unknown"
    ModelName      "Unknown"
    HorizSync       28.0 - 33.0
    VertRefresh     43.0 - 72.0
    Option         "DPMS"
EndSection

Section "Device"
    Identifier     "Device0"
    Driver         "nvidia"
    VendorName     "NVIDIA Corporation"
    Option      "TwinViewXineramaInfoOrder" "DFP"
EndSection

Section "Screen"
    Identifier     "Screen0"
    Device         "Device0"
    Monitor        "Monitor0"
    DefaultDepth    24
    Option         "TwinView" "true"
    Option         "MetaModes" "nvidia-auto-select, nvidia-auto-select"
    SubSection     "Display"
        Depth       24
        Modes         "1920x1200"
    EndSubSection
EndSection

...

Merci pour ton aide.