A patch is behind the second link. You apparently installed Xfce before updating the system.
There is a literature of this bug if you search the site, e.g.,
https://trisquel.info/forum/screen-tearing-and-high-cpu#comment-99720 and
https://trisquel.info/en/issues/7610
- [Trisquel-users] XFCE problems anew (anold!) jbahn
- [Trisquel-users] Re : XFCE problems anew (anold!) lcerf
- Re: [Trisquel-users] XFCE problems anew (anold!) jbahn
- [Trisquel-users] Re : XFCE problems anew (anold!) lcerf
- Re: [Trisquel-users] XFCE problems anew (anold!) jbahn
