I have an application (Graffer: https://github.com/jtappin/graffer.git) that uses plplot as its plotting engine, but when I try to use the script or symbol fonts (plsfont(PL_FCI_SCRIPT,...) or plsfont(PL_FCI_SYMBOL,...) I just get the regular Sans-serif font.

Is this because I don't have the needed fonts installed, or because the various cairo (and epsqt) drivers don't support them?

I am running Manjaro Linux and do have the ttf-ms-fonts package (and a good many other fonts) installed.