Add custom background to section in home page

Okay! Finally I have found the solution! (even if I don’t understand why we have to do this that way).

In fact we have not to modify the function.php file but the customizer.php with the code I quoted above (in the question).

Now I really feel released from that issue, but anyone could explain me why is it that file that we have to modify? I think I haven’t really understood the role of the differents files.

The inc subdirectory

The inc subdirectory content

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