Modal exclusive mode graphic application

Hi, I am quite new in Linux... and I am not able to find answer for this :

I have my c application - hello word / just one graphic window with close button ... simple.

I am able to start/run it from gui desktop as well as from terminal which I start in gui desktop. It just open graphic window, prints hello word into this window, show close button and after pressing button it close application. Thats all.

My idea is to use this upboard as embedded system, without any possibility to allow end user to use gui desktop, shell, terminal whatever ,... except of my application hello word right after boot ( by the other words, "to boot into my graphic application", which will I disable close button from -> no way to escape from it into os).

I am able to switch and boot ubilinux in text mode , without gui, however in this case, my application dont run, because there in no graphic display (error message with this meaning is there showed instead).

So the question is, how to boot linux and then automatic start my graphic application in this lets say "exclusive" mode , without gui desktop on background of this application ?
Is there any tutorial, how to create embedded graphic system with UPBoard ?
Thanks for ideas.