Comment 10 for bug 209358

It seems that this Qt version has hardcoded the generic type "Helvetica" as "Sans Serif". Helvetica is defined at /etc/fonts/conf.d/30-metric-aliases.conf as "Nimbus Sans L"

You can change it there or add to your ~/.fonts.conf the following stanzas:

        <alias binding="same">
          <family>Helvetica</family>
          <accept>
          <family>Arial</family>
          </accept>
        </alias>

Then refresh your font cache with fc-cache, restart your application and you should be watching a nice, crisp, hinted font.

Substitute Arial for the font of your choice. BEWARE: there are some consequences to this that I don't understand well because of font metrics and what not, read this bug for more information:

https://bugs.launchpad.net/ubuntu/+source/fontconfig/+bug/203824