- surface-userdata-raw surfaceprocedure
- set! (surface-userdata-raw surface) valsetter
- surface-userdata-raw-set! surface valsetter
Get or set the sdl2:surface's "userdata" field, as a pointer or #f.
If you want to store a pointer to a Scheme object here, be sure to evict the object first. Otherwise the object's location in memory might change, rendering the pointer invalid.