GtkStyle extendable?

[Dov Grobgeld <dov grobgeld gmail com>]

While playing around with pango, cairo and librsvg, I started thinking about how to wrap the result into a GtkLabel and how to set its properties. I then wondered whether GtkStyle is extendable? I.e. if I create a widget derived from GtkLabel called SvgLabel that has a property called Filter that describes what svg filter should be applied to it. Is it then possible to get it associated with a style property, e.g. filter="Bevel"? According to the GtkStyle documentation, a style is a fixed list of certain properties in a struct. Is it possible to "inherit" from this struct and add additional fields of my own that are somehow supported by the parser?

I think the use case is clear. I would like to be able in a style sheet to change all the SvgLabels named "foo*" to have filter "bevel" and all "bar" widgets to have filter "drow-shadow".

Thanks!
Dov