I had a quick look at the code, and I've immediately found a
fundamental problem: You are directly accessing
`library->svg_renderer_state`. This is a no-go for applications since
`FT_Library` is an opaque pointer that must not be dereferenced.
Is it actually necessary that `svg_renderer_state` is a member of
`FT_Library`? Your SVG code doesn't access it. If yes, we probably
need a driver property to pass the SVG renderer state structure back
and forth.
Basically, I use that location to store a structure that keeps some caching
data that the one hook writes to while the other one reads from. This avoids
computing the same thing again.
It's not really necessary to store it in FT_Library, if there's any other location
that all the hooks can access, it'd work fine. Do you have other candidates
to store the structure?