@kuriko
Turns out there is an extra comma in there ("int32_t, x"). So a typo on the website (which I copied).

But Although it compiles now I still could not figure out the last parameter. The doc says "uint8_t font" but thats something else then "IFont* font". What is 2 in your example?

It seems the official documentation (the Arduino Guide linked to the web page of the AtomS3R) is not correct. Am I doing something wrong or is this documentation wrong? It says:

drawChar
Draw an unicode character.

Syntax:

size_t drawChar(uint16_t uniCode, int32_t, x, int32_t y, uint8_t font)

But this doesn't compile. It should be something like: drawChar( x, y, char, color, color, zoom, zoom) (which seems to work fine)