c_cairo_device_set_user_data

Undocumented in source but is binding to C. You might be able to learn more by searching the web for its name.
__gshared extern (C)
cairo_status_t function(cairo_device_t* device, cairo_user_data_key_t* key, void* userData, cairo_destroy_func_t destroy) c_cairo_device_set_user_data;

Meta