I am considering using Rubyvis, a Ruby Port of the Protovis library, to generate plots for scientific publications. Rubyvis renders charts as SVG files. However, I haven't found a way to use subscripts or superscripts in text (such as diagram titles or axis labels).
The documentation for the Label class states:
The character data must be plain text (unicode), though the text can be styled using the font property. If rich text is needed, external HTML elements can be overlaid on the canvas by hand.
This sounds like the library itself does not support this functionality.
Is there a way to get subscripts and superscripts (and possible other rich text) directly in the output graphics file, when is is not embedded in a website?