X11/Xlib.h: No such file or directory

Thanks to all of you. I tried this way but can’t compile the geoviewer.
I got an error message
grafik

Flair works but no geoviewer is found.
Thanks
Dunja

Dear @d.j,

The error message is pretty straightforward: you are missing the package. You just need to install it. Search online for the installation instruction for your operative system.