I am booting a Pi 4 running the latest version of Raspbian Lite into Chromium kiosk mode and outputting the display to 2 monitors.

I have successfully hooked up the 2 monitors, but the displays are mirrored showing the same output on each screen.

My goal is to have an "extended" screen where Chromium goes fullscreen and is stretched equally across the 2 monitors.

To this point, I have made minimal configuration updates. I have used NOOBS to install Raspbian Lite. I then installed X Server, Openbox and Chromium. The Pi boots directly into Chromium in kiosk mode and loads the webpage as expected.

I have edited the Openbox config like:

xset s off
xset s noblank
xset -dpms

setxkbmap -option terminate:ctrl_alt_bksp

chromium-browser --disable-infobars --kiosk 'https.myurl.com'

And added a .bash_profile with:

[[ -z $DISPLAY && $XDG_VTNR -eq 1 ]] && startx
  • I'd start by researching xrandr, eg. magnatecha.com/dual-monitors-with-openbox-and-xrandr (not a solution but an intro to the concept). My first goal would be a continuous display, ie., one where Chromium probably comes up on only one screen. Using a mouse might help.
    – goldilocks
    Feb 11 '20 at 15:54
  • The title of your question is wrong. A RPi 4B cannot run with Raspbian Stretch. It has to use Raspbian Buster.
    – Ingo
    Feb 11 '20 at 18:20

Don't fiddle with the config files.

Run Screen Configuration which has options to configure both screens. (This is basically a front end to xrandr.)

This is a GUI but AFAIK the only way to configure multiple screens.

If you hadn't wasted space with NOOBS you would have plenty of room for Raspbian with Desktop.

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