Hi Werner,
Is there any chance you can modify FT_Set_Var_Design_Coordinates() to detect when the set face coordinates are not changed and shortcircuit out early? Currently, if one calls that function too often (say, for every glyph load, which is how we want to call it in cairo), it causes font metrics and autohinter reinitialization even if the coordinates didn't change. Can you please fix that? Matthias and I are hacking together this week, trying to finish font variations support in the Pango stack.