Rpi 4 and two monitors

NathTheDude

@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? :)

OldSunGuy

@NathTheDude The 2nd monitor should be display 0, screen 1. Use this:

DISPLAY=:0.1

NathTheDude

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.

OldSunGuy

@NathTheDude If you start a terminal on one desktop and run:

echo $DISPLAY

Then start a terminal on the other desktop and run:

echo $DISPLAY

do you get the same results?

NathTheDude

@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 :-/

NathTheDude

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

sdetweil

@NathTheDude if they are two independent desktops, then you should have a menu on the second desktop, just like the first…

also, you can move the mouse to the second desktop and do ctrl-alt-t to open a terminal there

I have an micro hdmi adapter coming later today so I can put up a second physical display on my pi4…

NathTheDude

@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.

sdetweil

@NathTheDude so, it looks like one big desktop…

u should be using Buster OS, right? so you can see the temples across the big image, some on the right display, some on the left…

NOT the same on both?

NathTheDude

@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.