Screen resolution - who is the master?

Hi
I’m currently under Zorin OS (linux).
Things are a little less smooth than with windows.
Today, connecting my computer to a video projector, I needed to change the screen resolution.
I choose a poorer resolution and all apps UI objects got bigger (normal).
However, when I switched back to a sharper resolution, all apps but OO went back to normal.


I uninstalled it, but it is still the same.
First, I though it was an OS issue, but:

  • all the apps are normal
  • a reboot changed nothing
  • re installing OO changed nothing (however I kept my user data).
    So right now I don’t know what is the cause off the issue : an OO parameter or an OS bug (but it seems unlikely.
    Thanks for your help.