In setting up Chromium in Kiosk mode I found that it was displaying off the screen. I have an 8" 800x600 display but Kiosk mode is set for 1280x720 in the /boot/dietpi.txt file.
I was wondering if when setting up kiosk mode a question is could ask, along side which web address to use, is what resolution to use/the resolution of the display? Mostly just to save having the jump into the config file separately.
Just a thought, ignore if it is a stupid idea! 
You could use these flags:
–window-size=800,600
chromium --app=<webadress> --window-size=800,600 --start-fullscreen --kiosk
But IDK how this will behave with the set resolution in dietpi.txt
Well resolution is automatically added from /boot/dietpi.txt into chromium start script. I guess the idea was to do it more interactive and ask the user via dialog instead of expecting the user to change resolution in /boot/dietpi.txt manually.
But in which dialog? 
I meant it can be set as start option, no need to fiddle with the dietpi.txt
the only way to set resolution for Chromium Kiosk mode is to adjust dietpi.txt
I guess the idea was to do this via autostart option as well. If selected to set Chromium as autostart, a dialog is open to ask for the web site to de displayed. Within the same dialog, a user should be ask for the resolution.
But is it not possible to use a custom autostart script with a line like
chromium-browser --kiosk --app= --window-size=800,600 --start-fullscreen
?
But is it not possible to use a custom autostart script with a line like
chromium-browser --kiosk --app= --window-size=800,600 --start-fullscreen
?
That would invent the wheel again as we have a script already doing this, once Chromium has been selected to automatically start.
/var/lib/dietpi/dietpi-software/installed/chromium-autostart.sh
I re-read the thread and now I get the full idea about the question, I didn’t know there is already a dialogue which asks for the webpage etc for the kiosk mode 
Happens 