INCLUDEPATH how it works ?

[wysota]

No, it doesn't fail with anything. It's just a place where to look for header fiiles. Your problem is not that some header files were not found.

[tonnot]

Thanks, WY (and sincerely thank you very much for your patience)
So finally, If you are going to use some custom widgets (using promoting aproach) be carefull to add 'by hand' all the dependant files, isn't it ?
Thanks again

[wysota]

Using custom widgets "using promoting approach" is no different than using them directly in hand-written C++ code. You always need to add the header and implementation file (provided they exist) to the project.