@sdetweil - ahhh. I need to do this from the desktop:

pi@MagicMirrors:~ $ xrandr -q
Screen 0: minimum 320 x 200, current 2160 x 1920, maximum 7680 x 7680
HDMI-1 connected primary 1080x1920+0+0 left (normal left inverted right x axis y axis) 477mm x 268mm
   1920x1080     60.00*+  60.00    50.00    59.94  
   1680x1050     59.88  
   1280x1024     75.02    60.02  
   1440x900      59.90  
   1280x960      60.00  
   1280x720      60.00    60.00    50.00    59.94  
   1024x768      75.03    70.07    60.00  
   832x624       74.55  
   800x600       72.19    75.00    60.32    56.25  
   720x576       50.00    50.00    50.00  
   720x480       60.00    60.00    59.94    59.94    59.94  
   640x480       75.00    72.81    66.67    60.00    59.94    59.94  
   720x400       70.08  
HDMI-2 connected 1080x1920+1080+0 right (normal left inverted right x axis y axis) 477mm x 268mm
   1920x1080     60.00*+  60.00    50.00    59.94  
   1680x1050     59.88  
   1280x1024     75.02    60.02  
   1440x900      59.90  
   1280x960      60.00  
   1280x720      60.00    60.00    50.00    59.94  
   1024x768      75.03    70.07    60.00  
   832x624       74.55  
   800x600       72.19    75.00    60.32    56.25  
   720x576       50.00    50.00    50.00  
   720x480       60.00    60.00    59.94    59.94    59.94  
   640x480       75.00    72.81    66.67    60.00    59.94    59.94  
   720x400       70.08  
pi@MagicMirrors:~ $ 

@sdetweil . I get the following when trying to run different xrandr commands:

Can't open display

@sdetweil , so I did the firmware update and rebooted.

Slightly different now but still can not quite get this to work. When I now run a terminal on screen 1 the output of ‘echo $DISPLAY’ is ‘:0.0’ and when I run the terminal on the 2nd window the output is ‘:0’. However the same is seen when I try to either user ‘0’ or ‘0.0’ in run.sh (mm gets display on the 1st monitor.

I have again tried to use different numbers (1,2,3 and 0.1, 0.2, 0.3) but again, these are not valid entries.

@NathTheDude said in Rpi 4 and two monitors:

@sdetweil , I opened up a terminal session on each screen and both indicated the same display was being used (:0).

From the ‘Appearance Settings’ window (‘Prefences’ > ‘Apprearance Settings’, there is a ‘Taskbar’ tab and in this tab you select which hdmi output you want the taskbar to be on. You can choose both.

Sorry, with my previous comment - I meant to say you ‘CANT’ choose both (taskbar can only be on one screen/output).

@sdetweil , yeah buster.

I can see temples on both screens, the image does not flow between screens. When looking at the 'Appearance Settings’, the is a tab for each HMDI with different settings but these are purely for what image is seen on the desktop. You can use the same image on both desktops however this is purely related to the desktop image or so is what I understand of it.

@sdetweil , I opened up a terminal session on each screen and both indicated the same display was being used (:0).

From the ‘Appearance Settings’ window (‘Prefences’ > ‘Apprearance Settings’, there is a ‘Taskbar’ tab and in this tab you select which hdmi output you want the taskbar to be on. You can choose both.

@OldSunGuy , sorry mis read your comment. Not sure how I would start a terminal on one screen and a different terminal on another.

@OldSunGuy - I get :0.0

I wonder if both screens are being seen as 0.0, if that is the case I guess I would expect the MM screen to cover both screens and not just the first :-/

Hey @OldSunGuy , thanks. ‘0’ and ‘0.0’ seem to be the first monitor however I get an error when I try anything else. So far I have tried using each of the following: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9

Each time I try to start npm (npm start) apart from when I use 0 or 0.0 I get the following (with the value reflecting the number I changed in ‘run-start.sh’):

(electron:2238): Gtk-WARNING **: 06:14:02.236: cannot open display: :0.1

@sdetweil - not sure if this is relevant but it does not seem to matter what value I set in ‘run-start.sh’, when I reboot the pi it will always start MM on the first screen. Should it not fail if it is using ‘run-start.sh’?

Also with an incorrect value being added to ‘run-start.sh’, when I run ‘mm.sh’ this always works and displays MM on the first screen.

okay, I think I understand it now. When I reboot it is using ‘mm.sh’, within mm.sh is the following:

cd ~/MagicMirror
DISPLAY=:0 npm start

Which I assume means that the ‘run-start.sh’ is not used during boot up?

When I change this value to anything other than 0, this will also fail with the same error seen when trying to run npm previously.

@sdetweil , so using ‘0’ or ‘0.0’ give the same result and start MM on the first monitor.

So far I have tried 1,2,3,4,5,6,7,8,9 and 0.1, 0.2, 0.3, 0.4, 0.5

How far do I go? :)