Font is not visible in TBrowser

ROOT
1

The font that appeared in the TBrowser and TTreeViewer is not clear and some letters are missing in the font. I am also attaching the screenshot. Please someone show me how to handle this problem.
Screenshot%20from%202019-06-22%2016-05-27

_ROOT Version:6
_Platform:Ubuntu 18.04
Compiler: Not Provided

2
3

That worked. Thanks a lot sir.

4

We have now (in the master) turned Xft on by default.