AlertWindow and kiosk mode

I’m working on a kiosk app for a Raspberry Pi (running Ubuntu Mate).

First minor niggle is I have to set the main window size to less than the monitor resolution for it to get into full-screen mode. Easy workaround though.

I’ve discovered that if I show an AlertWindow it takes the app out of full-screen mode, showing the taskbar etc, which is not ideal. Is there a way to avoid this? E.g. create a fake window component that is not actually an OS window?

(Obviously I can create a custom component, just wondering if there is any easy solution using AlertWindow)

Aren’t AlertWindows heavyweight, meaning they’re added to the desktop?

Yes that seems to be the case. Looks like I need a custom solution.