glad you sorted out all the problems: I always feel sorta guilty when someone have issues on something I worked on before...

for the disappearing tube a solution could be to just draw a switched off tube on the background (fondo.png).
The original plan for the nixies was to put some weird background and make the tube glass tranparencies do the tricks or replicate the user OS wallpaper to let people personalize the clock (ala window mode)

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In case anyone is curious to check how open a .png with c and sdl on the tablet here the clock minisource:
https://garage.maemo.org/frs/downloa...lock-0.0.3.tgz