Thanks Breakfastclub for the fast answer,
Effectively, what you describe as in the attached picture are the symptoms of my problems.
Thanks for the 2 workarounds, indeed, it works with "normal size" fonts.
The problem is that "normal" fonts are too small for my native laptop 13" screen in 1980x1200. That is why I'd like to set them to 120DPI (either of the 2 ways you describe).
Do you know if there is (will be) a corrective patch ?
Cheers,