OpenType features in Pango

[Jeremy Smith <jeremy blazonco com>]

I have written a simple program that takes some text and a (very small) 
subset of CSS attributes over stdin, applies the attributes, calculates 
layout dimensions, and draws the text to a PNG.  It works great -- and 
once I got used to it, Pango was very easy to use.
Now I want to try and add some OpenType features to my program.  For 
example, I want to be able to use glyph substitution for ligatures 
(first priority) and stylistic sets (lower priority, but I imagine the 
methodology is similar to ligatures).
How difficult is it to use these features from Pango?  I've done some 
pretty exhaustive googling but I couldn't find any info on glyph 
substitution other than for language purposes.  Does anyone have an 
example they could point to?
Thanks so much!
Jeremy

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