Sorry I was not clear (and maybe in the wrong forum), I'm coding in C (platformIO).
But I'll try to use UiFlow and compare if I see the same behavior. I guess that the core primitive are the same so it may show me the good way.
I could not figure out how to handle text modifications on the screen. After changing the text, I still can see the text previously written in the background, so it's quite unreadable.
Do I have to use the drawing function to first clear the zone ?